Dynamic trace id was introduced in coresight subsystem, so trace id is
allocated dynamically. However, some hardware ATB source has static trace
id and it cannot be changed via software programming. For such source,
it can call coresight_get_static_trace_id to get the fixed trace id from
device node and pass id to coresight_trace_id_get_static_system_id to
reserve the id.

Signed-off-by: Mao Jinlong <quic_jinlmao@quicinc.com>
---
 .../hwtracing/coresight/coresight-platform.c  | 26 +++++++++++++
 .../hwtracing/coresight/coresight-trace-id.c  | 38 ++++++++++++++-----
 .../hwtracing/coresight/coresight-trace-id.h  |  9 +++++
 include/linux/coresight.h                     |  1 +
 4 files changed, 64 insertions(+), 10 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-platform.c b/drivers/hwtracing/coresight/coresight-platform.c
index 64e171eaad82..703abf0fa3f9 100644
--- a/drivers/hwtracing/coresight/coresight-platform.c
+++ b/drivers/hwtracing/coresight/coresight-platform.c
@@ -183,6 +183,18 @@ static int of_coresight_get_cpu(struct device *dev)
 	return cpu;
 }
 
+/*
+ * of_coresight_get_trace_id: Get the atid of a source device.
+ *
+ * Returns 0 on success.
+ */
+static int of_coresight_get_static_trace_id(struct device *dev, u32 *id)
+{
+
+	return of_property_read_u32(dev->of_node, "arm,static-trace-id", id);
+}
+
+
 /*
  * of_coresight_parse_endpoint : Parse the given output endpoint @ep
  * and fill the connection information in @pdata->out_conns
@@ -317,6 +329,11 @@ static inline int of_coresight_get_cpu(struct device *dev)
 {
 	return -ENODEV;
 }
+
+static inline int of_coresight_get_static_trace_id(struct device *dev, u32 *id)
+{
+	return -ENODEV;
+}
 #endif
 
 #ifdef CONFIG_ACPI
@@ -796,6 +813,15 @@ int coresight_get_cpu(struct device *dev)
 }
 EXPORT_SYMBOL_GPL(coresight_get_cpu);
 
+int coresight_get_static_trace_id(struct device *dev, u32 *id)
+{
+	if (!is_of_node(dev->fwnode))
+		return -EINVAL;
+
+	return of_coresight_get_static_trace_id(dev, id);
+}
+EXPORT_SYMBOL_GPL(coresight_get_static_trace_id);
+
 struct coresight_platform_data *
 coresight_get_platform_data(struct device *dev)
 {
diff --git a/drivers/hwtracing/coresight/coresight-trace-id.c b/drivers/hwtracing/coresight/coresight-trace-id.c
index af5b4ef59cea..ca3c3de4683e 100644
--- a/drivers/hwtracing/coresight/coresight-trace-id.c
+++ b/drivers/hwtracing/coresight/coresight-trace-id.c
@@ -11,6 +11,12 @@
 
 #include "coresight-trace-id.h"
 
+enum trace_id_flags {
+	TRACE_ID_ANY = 0x0,
+	TRACE_ID_PREFER_ODD = 0x1,
+	TRACE_ID_REQ_STATIC = 0x2,
+};
+
 /* Default trace ID map. Used on systems that don't require per sink mappings */
 static struct coresight_trace_id_map id_map_default;
 
@@ -80,16 +86,19 @@ static int coresight_trace_id_find_odd_id(struct coresight_trace_id_map *id_map)
  * Otherwise allocate next available ID.
  */
 static int coresight_trace_id_alloc_new_id(struct coresight_trace_id_map *id_map,
-					   int preferred_id, bool prefer_odd_id)
+					   int preferred_id, unsigned int flags)
 {
 	int id = 0;
 
 	/* for backwards compatibility, cpu IDs may use preferred value */
-	if (IS_VALID_CS_TRACE_ID(preferred_id) &&
-	    !test_bit(preferred_id, id_map->used_ids)) {
-		id = preferred_id;
-		goto trace_id_allocated;
-	} else if (prefer_odd_id) {
+	if (IS_VALID_CS_TRACE_ID(preferred_id)) {
+		if (!test_bit(preferred_id, id_map->used_ids)) {
+			id = preferred_id;
+			goto trace_id_allocated;
+		} else if (WARN((flags & TRACE_ID_REQ_STATIC), "Trace ID %d is used.\n",
+					preferred_id))
+			return -EINVAL;
+	} else if (flags & TRACE_ID_PREFER_ODD) {
 	/* may use odd ids to avoid preferred legacy cpu IDs */
 		id = coresight_trace_id_find_odd_id(id_map);
 		if (id)
@@ -175,7 +184,7 @@ static int coresight_trace_id_map_get_cpu_id(int cpu, struct coresight_trace_id_
 	 */
 	id = coresight_trace_id_alloc_new_id(id_map,
 					     CORESIGHT_LEGACY_CPU_TRACE_ID(cpu),
-					     false);
+					     TRACE_ID_ANY);
 	if (!IS_VALID_CS_TRACE_ID(id))
 		goto get_cpu_id_out_unlock;
 
@@ -222,14 +231,15 @@ static void coresight_trace_id_map_put_cpu_id(int cpu, struct coresight_trace_id
 	DUMP_ID_MAP(id_map);
 }
 
-static int coresight_trace_id_map_get_system_id(struct coresight_trace_id_map *id_map)
+static int coresight_trace_id_map_get_system_id(struct coresight_trace_id_map *id_map,
+					int preferred_id, unsigned int traceid_flags)
 {
 	unsigned long flags;
 	int id;
 
 	spin_lock_irqsave(&id_map_lock, flags);
 	/* prefer odd IDs for system components to avoid legacy CPU IDS */
-	id = coresight_trace_id_alloc_new_id(id_map, 0, true);
+	id = coresight_trace_id_alloc_new_id(id_map, preferred_id, traceid_flags);
 	spin_unlock_irqrestore(&id_map_lock, flags);
 
 	DUMP_ID(id);
@@ -271,10 +281,18 @@ EXPORT_SYMBOL_GPL(coresight_trace_id_read_cpu_id);
 
 int coresight_trace_id_get_system_id(void)
 {
-	return coresight_trace_id_map_get_system_id(&id_map_default);
+	return coresight_trace_id_map_get_system_id(&id_map_default, 0,
+			TRACE_ID_PREFER_ODD);
 }
 EXPORT_SYMBOL_GPL(coresight_trace_id_get_system_id);
 
+int coresight_trace_id_get_static_system_id(int trace_id)
+{
+	return coresight_trace_id_map_get_system_id(&id_map_default,
+			trace_id, TRACE_ID_REQ_STATIC);
+}
+EXPORT_SYMBOL_GPL(coresight_trace_id_get_static_system_id);
+
 void coresight_trace_id_put_system_id(int id)
 {
 	coresight_trace_id_map_put_system_id(&id_map_default, id);
diff --git a/drivers/hwtracing/coresight/coresight-trace-id.h b/drivers/hwtracing/coresight/coresight-trace-id.h
index 3797777d367e..ca2fdf31c835 100644
--- a/drivers/hwtracing/coresight/coresight-trace-id.h
+++ b/drivers/hwtracing/coresight/coresight-trace-id.h
@@ -122,6 +122,15 @@ int coresight_trace_id_read_cpu_id(int cpu);
  */
 int coresight_trace_id_get_system_id(void);
 
+/**
+ * Allocate a CoreSight static trace ID for a system component.
+ *
+ * Used to allocate static IDs for system trace sources such as dummy source.
+ *
+ * return: Trace ID or -EINVAL if allocation is impossible.
+ */
+int coresight_trace_id_get_static_system_id(int id);
+
 /**
  * Release an allocated system trace ID.
  *
diff --git a/include/linux/coresight.h b/include/linux/coresight.h
index f09ace92176e..2cdc0b1cd536 100644
--- a/include/linux/coresight.h
+++ b/include/linux/coresight.h
@@ -643,6 +643,7 @@ void coresight_relaxed_write64(struct coresight_device *csdev,
 void coresight_write64(struct coresight_device *csdev, u64 val, u32 offset);
 
 extern int coresight_get_cpu(struct device *dev);
+extern int coresight_get_static_trace_id(struct device *dev, u32 *id);
 
 struct coresight_platform_data *coresight_get_platform_data(struct device *dev);
 struct coresight_connection *
-- 
2.46.0

On 10/09/2024 11:01, Mao Jinlong wrote:
> Dynamic trace id was introduced in coresight subsystem, so trace id is
> allocated dynamically. However, some hardware ATB source has static trace
> id and it cannot be changed via software programming. For such source,
> it can call coresight_get_static_trace_id to get the fixed trace id from
> device node and pass id to coresight_trace_id_get_static_system_id to
> reserve the id.
> 
> Signed-off-by: Mao Jinlong <quic_jinlmao@quicinc.com>

This patch is technically doing two different things :

1. Support for reading the static traceid from the firmware. (users of 
which comes later in Dummy)

2. Support for allocating a "specific" traceid for system sources.


Both the names are a bit similar and could be confusing.

For (1), I don't think we need to add a helper like that. See my 
comments below, and drop all of that from here this patch.


> ---
>   .../hwtracing/coresight/coresight-platform.c  | 26 +++++++++++++
>   .../hwtracing/coresight/coresight-trace-id.c  | 38 ++++++++++++++-----
>   .../hwtracing/coresight/coresight-trace-id.h  |  9 +++++
>   include/linux/coresight.h                     |  1 +
>   4 files changed, 64 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/hwtracing/coresight/coresight-platform.c b/drivers/hwtracing/coresight/coresight-platform.c
> index 64e171eaad82..703abf0fa3f9 100644
> --- a/drivers/hwtracing/coresight/coresight-platform.c
> +++ b/drivers/hwtracing/coresight/coresight-platform.c
> @@ -183,6 +183,18 @@ static int of_coresight_get_cpu(struct device *dev)
>   	return cpu;
>   }
>   
> +/*
> + * of_coresight_get_trace_id: Get the atid of a source device.
> + *
> + * Returns 0 on success.
> + */
> +static int of_coresight_get_static_trace_id(struct device *dev, u32 *id)
> +{
> +
> +	return of_property_read_u32(dev->of_node, "arm,static-trace-id", id);
> +}
> +
> +
>   /*
>    * of_coresight_parse_endpoint : Parse the given output endpoint @ep
>    * and fill the connection information in @pdata->out_conns
> @@ -317,6 +329,11 @@ static inline int of_coresight_get_cpu(struct device *dev)
>   {
>   	return -ENODEV;
>   }
> +
> +static inline int of_coresight_get_static_trace_id(struct device *dev, u32 *id)
> +{
> +	return -ENODEV;
> +}
>   #endif


>   
>   #ifdef CONFIG_ACPI
> @@ -796,6 +813,15 @@ int coresight_get_cpu(struct device *dev)
>   }
>   EXPORT_SYMBOL_GPL(coresight_get_cpu);
>   
> +int coresight_get_static_trace_id(struct device *dev, u32 *id)
> +{
> +	if (!is_of_node(dev->fwnode))
> +		return -EINVAL;
> +
> +	return of_coresight_get_static_trace_id(dev, id);

Please could we not directly use :

fwnode_property_read_u32(dev_fwnode(dev), "arm,static-trace-id", 
&traceid) in the dummy driver ?

The rest looks fine to me.

Suzuki


> +}
> +EXPORT_SYMBOL_GPL(coresight_get_static_trace_id);
> +
>   struct coresight_platform_data *
>   coresight_get_platform_data(struct device *dev)
>   {
> diff --git a/drivers/hwtracing/coresight/coresight-trace-id.c b/drivers/hwtracing/coresight/coresight-trace-id.c
> index af5b4ef59cea..ca3c3de4683e 100644
> --- a/drivers/hwtracing/coresight/coresight-trace-id.c
> +++ b/drivers/hwtracing/coresight/coresight-trace-id.c
> @@ -11,6 +11,12 @@
>   
>   #include "coresight-trace-id.h"
>   
> +enum trace_id_flags {
> +	TRACE_ID_ANY = 0x0,
> +	TRACE_ID_PREFER_ODD = 0x1,
> +	TRACE_ID_REQ_STATIC = 0x2,
> +};
> +
>   /* Default trace ID map. Used on systems that don't require per sink mappings */
>   static struct coresight_trace_id_map id_map_default;
>   
> @@ -80,16 +86,19 @@ static int coresight_trace_id_find_odd_id(struct coresight_trace_id_map *id_map)
>    * Otherwise allocate next available ID.
>    */
>   static int coresight_trace_id_alloc_new_id(struct coresight_trace_id_map *id_map,
> -					   int preferred_id, bool prefer_odd_id)
> +					   int preferred_id, unsigned int flags)
>   {
>   	int id = 0;
>   
>   	/* for backwards compatibility, cpu IDs may use preferred value */
> -	if (IS_VALID_CS_TRACE_ID(preferred_id) &&
> -	    !test_bit(preferred_id, id_map->used_ids)) {
> -		id = preferred_id;
> -		goto trace_id_allocated;
> -	} else if (prefer_odd_id) {
> +	if (IS_VALID_CS_TRACE_ID(preferred_id)) {
> +		if (!test_bit(preferred_id, id_map->used_ids)) {
> +			id = preferred_id;
> +			goto trace_id_allocated;
> +		} else if (WARN((flags & TRACE_ID_REQ_STATIC), "Trace ID %d is used.\n",
> +					preferred_id))
> +			return -EINVAL;
> +	} else if (flags & TRACE_ID_PREFER_ODD) {
>   	/* may use odd ids to avoid preferred legacy cpu IDs */
>   		id = coresight_trace_id_find_odd_id(id_map);
>   		if (id)
> @@ -175,7 +184,7 @@ static int coresight_trace_id_map_get_cpu_id(int cpu, struct coresight_trace_id_
>   	 */
>   	id = coresight_trace_id_alloc_new_id(id_map,
>   					     CORESIGHT_LEGACY_CPU_TRACE_ID(cpu),
> -					     false);
> +					     TRACE_ID_ANY);
>   	if (!IS_VALID_CS_TRACE_ID(id))
>   		goto get_cpu_id_out_unlock;
>   
> @@ -222,14 +231,15 @@ static void coresight_trace_id_map_put_cpu_id(int cpu, struct coresight_trace_id
>   	DUMP_ID_MAP(id_map);
>   }
>   
> -static int coresight_trace_id_map_get_system_id(struct coresight_trace_id_map *id_map)
> +static int coresight_trace_id_map_get_system_id(struct coresight_trace_id_map *id_map,
> +					int preferred_id, unsigned int traceid_flags)
>   {
>   	unsigned long flags;
>   	int id;
>   
>   	spin_lock_irqsave(&id_map_lock, flags);
>   	/* prefer odd IDs for system components to avoid legacy CPU IDS */
> -	id = coresight_trace_id_alloc_new_id(id_map, 0, true);
> +	id = coresight_trace_id_alloc_new_id(id_map, preferred_id, traceid_flags);
>   	spin_unlock_irqrestore(&id_map_lock, flags);
>   
>   	DUMP_ID(id);
> @@ -271,10 +281,18 @@ EXPORT_SYMBOL_GPL(coresight_trace_id_read_cpu_id);
>   
>   int coresight_trace_id_get_system_id(void)
>   {
> -	return coresight_trace_id_map_get_system_id(&id_map_default);
> +	return coresight_trace_id_map_get_system_id(&id_map_default, 0,
> +			TRACE_ID_PREFER_ODD);
>   }
>   EXPORT_SYMBOL_GPL(coresight_trace_id_get_system_id);
>   
> +int coresight_trace_id_get_static_system_id(int trace_id)
> +{
> +	return coresight_trace_id_map_get_system_id(&id_map_default,
> +			trace_id, TRACE_ID_REQ_STATIC);
> +}
> +EXPORT_SYMBOL_GPL(coresight_trace_id_get_static_system_id);
> +
>   void coresight_trace_id_put_system_id(int id)
>   {
>   	coresight_trace_id_map_put_system_id(&id_map_default, id);
> diff --git a/drivers/hwtracing/coresight/coresight-trace-id.h b/drivers/hwtracing/coresight/coresight-trace-id.h
> index 3797777d367e..ca2fdf31c835 100644
> --- a/drivers/hwtracing/coresight/coresight-trace-id.h
> +++ b/drivers/hwtracing/coresight/coresight-trace-id.h
> @@ -122,6 +122,15 @@ int coresight_trace_id_read_cpu_id(int cpu);
>    */
>   int coresight_trace_id_get_system_id(void);
>   
> +/**
> + * Allocate a CoreSight static trace ID for a system component.
> + *
> + * Used to allocate static IDs for system trace sources such as dummy source.
> + *
> + * return: Trace ID or -EINVAL if allocation is impossible.
> + */
> +int coresight_trace_id_get_static_system_id(int id);
> +
>   /**
>    * Release an allocated system trace ID.
>    *
> diff --git a/include/linux/coresight.h b/include/linux/coresight.h
> index f09ace92176e..2cdc0b1cd536 100644
> --- a/include/linux/coresight.h
> +++ b/include/linux/coresight.h
> @@ -643,6 +643,7 @@ void coresight_relaxed_write64(struct coresight_device *csdev,
>   void coresight_write64(struct coresight_device *csdev, u64 val, u32 offset);
>   
>   extern int coresight_get_cpu(struct device *dev);
> +extern int coresight_get_static_trace_id(struct device *dev, u32 *id);
>   
>   struct coresight_platform_data *coresight_get_platform_data(struct device *dev);
>   struct coresight_connection *

On 2024/10/9 17:50, Suzuki K Poulose wrote:
> On 10/09/2024 11:01, Mao Jinlong wrote:
>> Dynamic trace id was introduced in coresight subsystem, so trace id is
>> allocated dynamically. However, some hardware ATB source has static trace
>> id and it cannot be changed via software programming. For such source,
>> it can call coresight_get_static_trace_id to get the fixed trace id from
>> device node and pass id to coresight_trace_id_get_static_system_id to
>> reserve the id.
>>
>> Signed-off-by: Mao Jinlong <quic_jinlmao@quicinc.com>
> 
> This patch is technically doing two different things :
> 
> 1. Support for reading the static traceid from the firmware. (users of 
> which comes later in Dummy)
> 
> 2. Support for allocating a "specific" traceid for system sources.
> 
> 
> Both the names are a bit similar and could be confusing.
> 
> For (1), I don't think we need to add a helper like that. See my 
> comments below, and drop all of that from here this patch.

Hi Suzuki,

This helper will be common for other new drivers in future.
Some other driver will use it, not only for dummy driver.

Thanks
Jinlong Mao

> 
> 
>> ---
>>   .../hwtracing/coresight/coresight-platform.c  | 26 +++++++++++++
>>   .../hwtracing/coresight/coresight-trace-id.c  | 38 ++++++++++++++-----
>>   .../hwtracing/coresight/coresight-trace-id.h  |  9 +++++
>>   include/linux/coresight.h                     |  1 +
>>   4 files changed, 64 insertions(+), 10 deletions(-)
>>
>> diff --git a/drivers/hwtracing/coresight/coresight-platform.c b/ 
>> drivers/hwtracing/coresight/coresight-platform.c
>> index 64e171eaad82..703abf0fa3f9 100644
>> --- a/drivers/hwtracing/coresight/coresight-platform.c
>> +++ b/drivers/hwtracing/coresight/coresight-platform.c
>> @@ -183,6 +183,18 @@ static int of_coresight_get_cpu(struct device *dev)
>>       return cpu;
>>   }
>> +/*
>> + * of_coresight_get_trace_id: Get the atid of a source device.
>> + *
>> + * Returns 0 on success.
>> + */
>> +static int of_coresight_get_static_trace_id(struct device *dev, u32 *id)
>> +{
>> +
>> +    return of_property_read_u32(dev->of_node, "arm,static-trace-id", 
>> id);
>> +}
>> +
>> +
>>   /*
>>    * of_coresight_parse_endpoint : Parse the given output endpoint @ep
>>    * and fill the connection information in @pdata->out_conns
>> @@ -317,6 +329,11 @@ static inline int of_coresight_get_cpu(struct 
>> device *dev)
>>   {
>>       return -ENODEV;
>>   }
>> +
>> +static inline int of_coresight_get_static_trace_id(struct device 
>> *dev, u32 *id)
>> +{
>> +    return -ENODEV;
>> +}
>>   #endif
> 
> 
>>   #ifdef CONFIG_ACPI
>> @@ -796,6 +813,15 @@ int coresight_get_cpu(struct device *dev)
>>   }
>>   EXPORT_SYMBOL_GPL(coresight_get_cpu);
>> +int coresight_get_static_trace_id(struct device *dev, u32 *id)
>> +{
>> +    if (!is_of_node(dev->fwnode))
>> +        return -EINVAL;
>> +
>> +    return of_coresight_get_static_trace_id(dev, id);
> 
> Please could we not directly use :
> 
> fwnode_property_read_u32(dev_fwnode(dev), "arm,static-trace-id", 
> &traceid) in the dummy driver ?
> 
> The rest looks fine to me.
> 
> Suzuki
> 
> 
>> +}
>> +EXPORT_SYMBOL_GPL(coresight_get_static_trace_id);
>> +
>>   struct coresight_platform_data *
>>   coresight_get_platform_data(struct device *dev)
>>   {
>> diff --git a/drivers/hwtracing/coresight/coresight-trace-id.c b/ 
>> drivers/hwtracing/coresight/coresight-trace-id.c
>> index af5b4ef59cea..ca3c3de4683e 100644
>> --- a/drivers/hwtracing/coresight/coresight-trace-id.c
>> +++ b/drivers/hwtracing/coresight/coresight-trace-id.c
>> @@ -11,6 +11,12 @@
>>   #include "coresight-trace-id.h"
>> +enum trace_id_flags {
>> +    TRACE_ID_ANY = 0x0,
>> +    TRACE_ID_PREFER_ODD = 0x1,
>> +    TRACE_ID_REQ_STATIC = 0x2,
>> +};
>> +
>>   /* Default trace ID map. Used on systems that don't require per sink 
>> mappings */
>>   static struct coresight_trace_id_map id_map_default;
>> @@ -80,16 +86,19 @@ static int coresight_trace_id_find_odd_id(struct 
>> coresight_trace_id_map *id_map)
>>    * Otherwise allocate next available ID.
>>    */
>>   static int coresight_trace_id_alloc_new_id(struct 
>> coresight_trace_id_map *id_map,
>> -                       int preferred_id, bool prefer_odd_id)
>> +                       int preferred_id, unsigned int flags)
>>   {
>>       int id = 0;
>>       /* for backwards compatibility, cpu IDs may use preferred value */
>> -    if (IS_VALID_CS_TRACE_ID(preferred_id) &&
>> -        !test_bit(preferred_id, id_map->used_ids)) {
>> -        id = preferred_id;
>> -        goto trace_id_allocated;
>> -    } else if (prefer_odd_id) {
>> +    if (IS_VALID_CS_TRACE_ID(preferred_id)) {
>> +        if (!test_bit(preferred_id, id_map->used_ids)) {
>> +            id = preferred_id;
>> +            goto trace_id_allocated;
>> +        } else if (WARN((flags & TRACE_ID_REQ_STATIC), "Trace ID %d 
>> is used.\n",
>> +                    preferred_id))
>> +            return -EINVAL;
>> +    } else if (flags & TRACE_ID_PREFER_ODD) {
>>       /* may use odd ids to avoid preferred legacy cpu IDs */
>>           id = coresight_trace_id_find_odd_id(id_map);
>>           if (id)
>> @@ -175,7 +184,7 @@ static int coresight_trace_id_map_get_cpu_id(int 
>> cpu, struct coresight_trace_id_
>>        */
>>       id = coresight_trace_id_alloc_new_id(id_map,
>>                            CORESIGHT_LEGACY_CPU_TRACE_ID(cpu),
>> -                         false);
>> +                         TRACE_ID_ANY);
>>       if (!IS_VALID_CS_TRACE_ID(id))
>>           goto get_cpu_id_out_unlock;
>> @@ -222,14 +231,15 @@ static void 
>> coresight_trace_id_map_put_cpu_id(int cpu, struct coresight_trace_id
>>       DUMP_ID_MAP(id_map);
>>   }
>> -static int coresight_trace_id_map_get_system_id(struct 
>> coresight_trace_id_map *id_map)
>> +static int coresight_trace_id_map_get_system_id(struct 
>> coresight_trace_id_map *id_map,
>> +                    int preferred_id, unsigned int traceid_flags)
>>   {
>>       unsigned long flags;
>>       int id;
>>       spin_lock_irqsave(&id_map_lock, flags);
>>       /* prefer odd IDs for system components to avoid legacy CPU IDS */
>> -    id = coresight_trace_id_alloc_new_id(id_map, 0, true);
>> +    id = coresight_trace_id_alloc_new_id(id_map, preferred_id, 
>> traceid_flags);
>>       spin_unlock_irqrestore(&id_map_lock, flags);
>>       DUMP_ID(id);
>> @@ -271,10 +281,18 @@ EXPORT_SYMBOL_GPL(coresight_trace_id_read_cpu_id);
>>   int coresight_trace_id_get_system_id(void)
>>   {
>> -    return coresight_trace_id_map_get_system_id(&id_map_default);
>> +    return coresight_trace_id_map_get_system_id(&id_map_default, 0,
>> +            TRACE_ID_PREFER_ODD);
>>   }
>>   EXPORT_SYMBOL_GPL(coresight_trace_id_get_system_id);
>> +int coresight_trace_id_get_static_system_id(int trace_id)
>> +{
>> +    return coresight_trace_id_map_get_system_id(&id_map_default,
>> +            trace_id, TRACE_ID_REQ_STATIC);
>> +}
>> +EXPORT_SYMBOL_GPL(coresight_trace_id_get_static_system_id);
>> +
>>   void coresight_trace_id_put_system_id(int id)
>>   {
>>       coresight_trace_id_map_put_system_id(&id_map_default, id);
>> diff --git a/drivers/hwtracing/coresight/coresight-trace-id.h b/ 
>> drivers/hwtracing/coresight/coresight-trace-id.h
>> index 3797777d367e..ca2fdf31c835 100644
>> --- a/drivers/hwtracing/coresight/coresight-trace-id.h
>> +++ b/drivers/hwtracing/coresight/coresight-trace-id.h
>> @@ -122,6 +122,15 @@ int coresight_trace_id_read_cpu_id(int cpu);
>>    */
>>   int coresight_trace_id_get_system_id(void);
>> +/**
>> + * Allocate a CoreSight static trace ID for a system component.
>> + *
>> + * Used to allocate static IDs for system trace sources such as dummy 
>> source.
>> + *
>> + * return: Trace ID or -EINVAL if allocation is impossible.
>> + */
>> +int coresight_trace_id_get_static_system_id(int id);
>> +
>>   /**
>>    * Release an allocated system trace ID.
>>    *
>> diff --git a/include/linux/coresight.h b/include/linux/coresight.h
>> index f09ace92176e..2cdc0b1cd536 100644
>> --- a/include/linux/coresight.h
>> +++ b/include/linux/coresight.h
>> @@ -643,6 +643,7 @@ void coresight_relaxed_write64(struct 
>> coresight_device *csdev,
>>   void coresight_write64(struct coresight_device *csdev, u64 val, u32 
>> offset);
>>   extern int coresight_get_cpu(struct device *dev);
>> +extern int coresight_get_static_trace_id(struct device *dev, u32 *id);
>>   struct coresight_platform_data *coresight_get_platform_data(struct 
>> device *dev);
>>   struct coresight_connection *
> 

On 09/10/2024 11:37, Jinlong Mao wrote:
> 
> 
> On 2024/10/9 17:50, Suzuki K Poulose wrote:
>> On 10/09/2024 11:01, Mao Jinlong wrote:
>>> Dynamic trace id was introduced in coresight subsystem, so trace id is
>>> allocated dynamically. However, some hardware ATB source has static 
>>> trace
>>> id and it cannot be changed via software programming. For such source,
>>> it can call coresight_get_static_trace_id to get the fixed trace id from
>>> device node and pass id to coresight_trace_id_get_static_system_id to
>>> reserve the id.
>>>
>>> Signed-off-by: Mao Jinlong <quic_jinlmao@quicinc.com>
>>
>> This patch is technically doing two different things :
>>
>> 1. Support for reading the static traceid from the firmware. (users of 
>> which comes later in Dummy)
>>
>> 2. Support for allocating a "specific" traceid for system sources.
>>
>>
>> Both the names are a bit similar and could be confusing.
>>
>> For (1), I don't think we need to add a helper like that. See my 
>> comments below, and drop all of that from here this patch.
> 
> Hi Suzuki,
> 
> This helper will be common for other new drivers in future.
> Some other driver will use it, not only for dummy driver.

Ok, fair enough. But couldn't we still use the fwnode_xx directly from
the "helper" rather than defining of_xxx. That way it should work for
ACPI based systems too.

> 
> Thanks
> Jinlong Mao
> 
>>
>>
>>> ---
>>>   .../hwtracing/coresight/coresight-platform.c  | 26 +++++++++++++
>>>   .../hwtracing/coresight/coresight-trace-id.c  | 38 ++++++++++++++-----
>>>   .../hwtracing/coresight/coresight-trace-id.h  |  9 +++++
>>>   include/linux/coresight.h                     |  1 +
>>>   4 files changed, 64 insertions(+), 10 deletions(-)
>>>
>>> diff --git a/drivers/hwtracing/coresight/coresight-platform.c b/ 
>>> drivers/hwtracing/coresight/coresight-platform.c
>>> index 64e171eaad82..703abf0fa3f9 100644
>>> --- a/drivers/hwtracing/coresight/coresight-platform.c
>>> +++ b/drivers/hwtracing/coresight/coresight-platform.c
>>> @@ -183,6 +183,18 @@ static int of_coresight_get_cpu(struct device *dev)
>>>       return cpu;
>>>   }
>>> +/*
>>> + * of_coresight_get_trace_id: Get the atid of a source device.
>>> + *
>>> + * Returns 0 on success.
>>> + */
>>> +static int of_coresight_get_static_trace_id(struct device *dev, u32 
>>> *id)
>>> +{
>>> +
>>> +    return of_property_read_u32(dev->of_node, "arm,static-trace-id", 
>>> id);
>>> +}
>>> +
>>> +

Drop these ^^


>>>   /*
>>>    * of_coresight_parse_endpoint : Parse the given output endpoint @ep
>>>    * and fill the connection information in @pdata->out_conns
>>> @@ -317,6 +329,11 @@ static inline int of_coresight_get_cpu(struct 
>>> device *dev)
>>>   {
>>>       return -ENODEV;
>>>   }
>>> +
>>> +static inline int of_coresight_get_static_trace_id(struct device 
>>> *dev, u32 *id)
>>> +{
>>> +    return -ENODEV;
>>> +}
>>>   #endif
>>
>>
>>>   #ifdef CONFIG_ACPI
>>> @@ -796,6 +813,15 @@ int coresight_get_cpu(struct device *dev)
>>>   }
>>>   EXPORT_SYMBOL_GPL(coresight_get_cpu);
>>> +int coresight_get_static_trace_id(struct device *dev, u32 *id)
>>> +{
>>> +    if (!is_of_node(dev->fwnode))
>>> +        return -EINVAL;
>>> +
>>> +    return of_coresight_get_static_trace_id(dev, id);
>>
>> Please could we not directly use :
>>
>> fwnode_property_read_u32(dev_fwnode(dev), "arm,static-trace-id", 
>> &traceid) in the dummy driver ?

	return fwnode_property_read_u32(dev_fwnode(dev), "arm,static-trace-id", 
id);


Suzuki


>>
>> The rest looks fine to me.
>>
>> Suzuki
>>
>>
>>> +}
>>> +EXPORT_SYMBOL_GPL(coresight_get_static_trace_id);
>>> +
>>>   struct coresight_platform_data *
>>>   coresight_get_platform_data(struct device *dev)
>>>   {
>>> diff --git a/drivers/hwtracing/coresight/coresight-trace-id.c b/ 
>>> drivers/hwtracing/coresight/coresight-trace-id.c
>>> index af5b4ef59cea..ca3c3de4683e 100644
>>> --- a/drivers/hwtracing/coresight/coresight-trace-id.c
>>> +++ b/drivers/hwtracing/coresight/coresight-trace-id.c
>>> @@ -11,6 +11,12 @@
>>>   #include "coresight-trace-id.h"
>>> +enum trace_id_flags {
>>> +    TRACE_ID_ANY = 0x0,
>>> +    TRACE_ID_PREFER_ODD = 0x1,
>>> +    TRACE_ID_REQ_STATIC = 0x2,
>>> +};
>>> +
>>>   /* Default trace ID map. Used on systems that don't require per 
>>> sink mappings */
>>>   static struct coresight_trace_id_map id_map_default;
>>> @@ -80,16 +86,19 @@ static int coresight_trace_id_find_odd_id(struct 
>>> coresight_trace_id_map *id_map)
>>>    * Otherwise allocate next available ID.
>>>    */
>>>   static int coresight_trace_id_alloc_new_id(struct 
>>> coresight_trace_id_map *id_map,
>>> -                       int preferred_id, bool prefer_odd_id)
>>> +                       int preferred_id, unsigned int flags)
>>>   {
>>>       int id = 0;
>>>       /* for backwards compatibility, cpu IDs may use preferred value */
>>> -    if (IS_VALID_CS_TRACE_ID(preferred_id) &&
>>> -        !test_bit(preferred_id, id_map->used_ids)) {
>>> -        id = preferred_id;
>>> -        goto trace_id_allocated;
>>> -    } else if (prefer_odd_id) {
>>> +    if (IS_VALID_CS_TRACE_ID(preferred_id)) {
>>> +        if (!test_bit(preferred_id, id_map->used_ids)) {
>>> +            id = preferred_id;
>>> +            goto trace_id_allocated;
>>> +        } else if (WARN((flags & TRACE_ID_REQ_STATIC), "Trace ID %d 
>>> is used.\n",
>>> +                    preferred_id))
>>> +            return -EINVAL;
>>> +    } else if (flags & TRACE_ID_PREFER_ODD) {
>>>       /* may use odd ids to avoid preferred legacy cpu IDs */
>>>           id = coresight_trace_id_find_odd_id(id_map);
>>>           if (id)
>>> @@ -175,7 +184,7 @@ static int coresight_trace_id_map_get_cpu_id(int 
>>> cpu, struct coresight_trace_id_
>>>        */
>>>       id = coresight_trace_id_alloc_new_id(id_map,
>>>                            CORESIGHT_LEGACY_CPU_TRACE_ID(cpu),
>>> -                         false);
>>> +                         TRACE_ID_ANY);
>>>       if (!IS_VALID_CS_TRACE_ID(id))
>>>           goto get_cpu_id_out_unlock;
>>> @@ -222,14 +231,15 @@ static void 
>>> coresight_trace_id_map_put_cpu_id(int cpu, struct coresight_trace_id
>>>       DUMP_ID_MAP(id_map);
>>>   }
>>> -static int coresight_trace_id_map_get_system_id(struct 
>>> coresight_trace_id_map *id_map)
>>> +static int coresight_trace_id_map_get_system_id(struct 
>>> coresight_trace_id_map *id_map,
>>> +                    int preferred_id, unsigned int traceid_flags)
>>>   {
>>>       unsigned long flags;
>>>       int id;
>>>       spin_lock_irqsave(&id_map_lock, flags);
>>>       /* prefer odd IDs for system components to avoid legacy CPU IDS */
>>> -    id = coresight_trace_id_alloc_new_id(id_map, 0, true);
>>> +    id = coresight_trace_id_alloc_new_id(id_map, preferred_id, 
>>> traceid_flags);
>>>       spin_unlock_irqrestore(&id_map_lock, flags);
>>>       DUMP_ID(id);
>>> @@ -271,10 +281,18 @@ EXPORT_SYMBOL_GPL(coresight_trace_id_read_cpu_id);
>>>   int coresight_trace_id_get_system_id(void)
>>>   {
>>> -    return coresight_trace_id_map_get_system_id(&id_map_default);
>>> +    return coresight_trace_id_map_get_system_id(&id_map_default, 0,
>>> +            TRACE_ID_PREFER_ODD);
>>>   }
>>>   EXPORT_SYMBOL_GPL(coresight_trace_id_get_system_id);
>>> +int coresight_trace_id_get_static_system_id(int trace_id)
>>> +{
>>> +    return coresight_trace_id_map_get_system_id(&id_map_default,
>>> +            trace_id, TRACE_ID_REQ_STATIC);
>>> +}
>>> +EXPORT_SYMBOL_GPL(coresight_trace_id_get_static_system_id);
>>> +
>>>   void coresight_trace_id_put_system_id(int id)
>>>   {
>>>       coresight_trace_id_map_put_system_id(&id_map_default, id);
>>> diff --git a/drivers/hwtracing/coresight/coresight-trace-id.h b/ 
>>> drivers/hwtracing/coresight/coresight-trace-id.h
>>> index 3797777d367e..ca2fdf31c835 100644
>>> --- a/drivers/hwtracing/coresight/coresight-trace-id.h
>>> +++ b/drivers/hwtracing/coresight/coresight-trace-id.h
>>> @@ -122,6 +122,15 @@ int coresight_trace_id_read_cpu_id(int cpu);
>>>    */
>>>   int coresight_trace_id_get_system_id(void);
>>> +/**
>>> + * Allocate a CoreSight static trace ID for a system component.
>>> + *
>>> + * Used to allocate static IDs for system trace sources such as 
>>> dummy source.
>>> + *
>>> + * return: Trace ID or -EINVAL if allocation is impossible.
>>> + */
>>> +int coresight_trace_id_get_static_system_id(int id);
>>> +
>>>   /**
>>>    * Release an allocated system trace ID.
>>>    *
>>> diff --git a/include/linux/coresight.h b/include/linux/coresight.h
>>> index f09ace92176e..2cdc0b1cd536 100644
>>> --- a/include/linux/coresight.h
>>> +++ b/include/linux/coresight.h
>>> @@ -643,6 +643,7 @@ void coresight_relaxed_write64(struct 
>>> coresight_device *csdev,
>>>   void coresight_write64(struct coresight_device *csdev, u64 val, u32 
>>> offset);
>>>   extern int coresight_get_cpu(struct device *dev);
>>> +extern int coresight_get_static_trace_id(struct device *dev, u32 *id);
>>>   struct coresight_platform_data *coresight_get_platform_data(struct 
>>> device *dev);
>>>   struct coresight_connection *
>>
> 

On 2024/10/10 17:19, Suzuki K Poulose wrote:
> On 09/10/2024 11:37, Jinlong Mao wrote:
>>
>>
>> On 2024/10/9 17:50, Suzuki K Poulose wrote:
>>> On 10/09/2024 11:01, Mao Jinlong wrote:
>>>> Dynamic trace id was introduced in coresight subsystem, so trace id is
>>>> allocated dynamically. However, some hardware ATB source has static 
>>>> trace
>>>> id and it cannot be changed via software programming. For such source,
>>>> it can call coresight_get_static_trace_id to get the fixed trace id 
>>>> from
>>>> device node and pass id to coresight_trace_id_get_static_system_id to
>>>> reserve the id.
>>>>
>>>> Signed-off-by: Mao Jinlong <quic_jinlmao@quicinc.com>
>>>
>>> This patch is technically doing two different things :
>>>
>>> 1. Support for reading the static traceid from the firmware. (users 
>>> of which comes later in Dummy)
>>>
>>> 2. Support for allocating a "specific" traceid for system sources.
>>>
>>>
>>> Both the names are a bit similar and could be confusing.
>>>
>>> For (1), I don't think we need to add a helper like that. See my 
>>> comments below, and drop all of that from here this patch.
>>
>> Hi Suzuki,
>>
>> This helper will be common for other new drivers in future.
>> Some other driver will use it, not only for dummy driver.
> 
> Ok, fair enough. But couldn't we still use the fwnode_xx directly from
> the "helper" rather than defining of_xxx. That way it should work for
> ACPI based systems too.
> 
Sure. I will use the fwnode_xx.

>>
>> Thanks
>> Jinlong Mao
>>
>>>
>>>
>>>> ---
>>>>   .../hwtracing/coresight/coresight-platform.c  | 26 +++++++++++++
>>>>   .../hwtracing/coresight/coresight-trace-id.c  | 38 +++++++++++++ 
>>>> +-----
>>>>   .../hwtracing/coresight/coresight-trace-id.h  |  9 +++++
>>>>   include/linux/coresight.h                     |  1 +
>>>>   4 files changed, 64 insertions(+), 10 deletions(-)
>>>>
>>>> diff --git a/drivers/hwtracing/coresight/coresight-platform.c b/ 
>>>> drivers/hwtracing/coresight/coresight-platform.c
>>>> index 64e171eaad82..703abf0fa3f9 100644
>>>> --- a/drivers/hwtracing/coresight/coresight-platform.c
>>>> +++ b/drivers/hwtracing/coresight/coresight-platform.c
>>>> @@ -183,6 +183,18 @@ static int of_coresight_get_cpu(struct device 
>>>> *dev)
>>>>       return cpu;
>>>>   }
>>>> +/*
>>>> + * of_coresight_get_trace_id: Get the atid of a source device.
>>>> + *
>>>> + * Returns 0 on success.
>>>> + */
>>>> +static int of_coresight_get_static_trace_id(struct device *dev, u32 
>>>> *id)
>>>> +{
>>>> +
>>>> +    return of_property_read_u32(dev->of_node, "arm,static-trace- 
>>>> id", id);
>>>> +}
>>>> +
>>>> +
> 
> Drop these ^^
> 
> 
>>>>   /*
>>>>    * of_coresight_parse_endpoint : Parse the given output endpoint @ep
>>>>    * and fill the connection information in @pdata->out_conns
>>>> @@ -317,6 +329,11 @@ static inline int of_coresight_get_cpu(struct 
>>>> device *dev)
>>>>   {
>>>>       return -ENODEV;
>>>>   }
>>>> +
>>>> +static inline int of_coresight_get_static_trace_id(struct device 
>>>> *dev, u32 *id)
>>>> +{
>>>> +    return -ENODEV;
>>>> +}
>>>>   #endif
>>>
>>>
>>>>   #ifdef CONFIG_ACPI
>>>> @@ -796,6 +813,15 @@ int coresight_get_cpu(struct device *dev)
>>>>   }
>>>>   EXPORT_SYMBOL_GPL(coresight_get_cpu);
>>>> +int coresight_get_static_trace_id(struct device *dev, u32 *id)
>>>> +{
>>>> +    if (!is_of_node(dev->fwnode))
>>>> +        return -EINVAL;
>>>> +
>>>> +    return of_coresight_get_static_trace_id(dev, id);
>>>
>>> Please could we not directly use :
>>>
>>> fwnode_property_read_u32(dev_fwnode(dev), "arm,static-trace-id", 
>>> &traceid) in the dummy driver ?
> 
>      return fwnode_property_read_u32(dev_fwnode(dev), "arm,static-trace- 
> id", id);
> 
> 
> Suzuki
> 
> 
>>>
>>> The rest looks fine to me.
>>>
>>> Suzuki
>>>
>>>
>>>> +}
>>>> +EXPORT_SYMBOL_GPL(coresight_get_static_trace_id);
>>>> +
>>>>   struct coresight_platform_data *
>>>>   coresight_get_platform_data(struct device *dev)
>>>>   {
>>>> diff --git a/drivers/hwtracing/coresight/coresight-trace-id.c b/ 
>>>> drivers/hwtracing/coresight/coresight-trace-id.c
>>>> index af5b4ef59cea..ca3c3de4683e 100644
>>>> --- a/drivers/hwtracing/coresight/coresight-trace-id.c
>>>> +++ b/drivers/hwtracing/coresight/coresight-trace-id.c
>>>> @@ -11,6 +11,12 @@
>>>>   #include "coresight-trace-id.h"
>>>> +enum trace_id_flags {
>>>> +    TRACE_ID_ANY = 0x0,
>>>> +    TRACE_ID_PREFER_ODD = 0x1,
>>>> +    TRACE_ID_REQ_STATIC = 0x2,
>>>> +};
>>>> +
>>>>   /* Default trace ID map. Used on systems that don't require per 
>>>> sink mappings */
>>>>   static struct coresight_trace_id_map id_map_default;
>>>> @@ -80,16 +86,19 @@ static int coresight_trace_id_find_odd_id(struct 
>>>> coresight_trace_id_map *id_map)
>>>>    * Otherwise allocate next available ID.
>>>>    */
>>>>   static int coresight_trace_id_alloc_new_id(struct 
>>>> coresight_trace_id_map *id_map,
>>>> -                       int preferred_id, bool prefer_odd_id)
>>>> +                       int preferred_id, unsigned int flags)
>>>>   {
>>>>       int id = 0;
>>>>       /* for backwards compatibility, cpu IDs may use preferred 
>>>> value */
>>>> -    if (IS_VALID_CS_TRACE_ID(preferred_id) &&
>>>> -        !test_bit(preferred_id, id_map->used_ids)) {
>>>> -        id = preferred_id;
>>>> -        goto trace_id_allocated;
>>>> -    } else if (prefer_odd_id) {
>>>> +    if (IS_VALID_CS_TRACE_ID(preferred_id)) {
>>>> +        if (!test_bit(preferred_id, id_map->used_ids)) {
>>>> +            id = preferred_id;
>>>> +            goto trace_id_allocated;
>>>> +        } else if (WARN((flags & TRACE_ID_REQ_STATIC), "Trace ID %d 
>>>> is used.\n",
>>>> +                    preferred_id))
>>>> +            return -EINVAL;
>>>> +    } else if (flags & TRACE_ID_PREFER_ODD) {
>>>>       /* may use odd ids to avoid preferred legacy cpu IDs */
>>>>           id = coresight_trace_id_find_odd_id(id_map);
>>>>           if (id)
>>>> @@ -175,7 +184,7 @@ static int coresight_trace_id_map_get_cpu_id(int 
>>>> cpu, struct coresight_trace_id_
>>>>        */
>>>>       id = coresight_trace_id_alloc_new_id(id_map,
>>>>                            CORESIGHT_LEGACY_CPU_TRACE_ID(cpu),
>>>> -                         false);
>>>> +                         TRACE_ID_ANY);
>>>>       if (!IS_VALID_CS_TRACE_ID(id))
>>>>           goto get_cpu_id_out_unlock;
>>>> @@ -222,14 +231,15 @@ static void 
>>>> coresight_trace_id_map_put_cpu_id(int cpu, struct coresight_trace_id
>>>>       DUMP_ID_MAP(id_map);
>>>>   }
>>>> -static int coresight_trace_id_map_get_system_id(struct 
>>>> coresight_trace_id_map *id_map)
>>>> +static int coresight_trace_id_map_get_system_id(struct 
>>>> coresight_trace_id_map *id_map,
>>>> +                    int preferred_id, unsigned int traceid_flags)
>>>>   {
>>>>       unsigned long flags;
>>>>       int id;
>>>>       spin_lock_irqsave(&id_map_lock, flags);
>>>>       /* prefer odd IDs for system components to avoid legacy CPU 
>>>> IDS */
>>>> -    id = coresight_trace_id_alloc_new_id(id_map, 0, true);
>>>> +    id = coresight_trace_id_alloc_new_id(id_map, preferred_id, 
>>>> traceid_flags);
>>>>       spin_unlock_irqrestore(&id_map_lock, flags);
>>>>       DUMP_ID(id);
>>>> @@ -271,10 +281,18 @@ 
>>>> EXPORT_SYMBOL_GPL(coresight_trace_id_read_cpu_id);
>>>>   int coresight_trace_id_get_system_id(void)
>>>>   {
>>>> -    return coresight_trace_id_map_get_system_id(&id_map_default);
>>>> +    return coresight_trace_id_map_get_system_id(&id_map_default, 0,
>>>> +            TRACE_ID_PREFER_ODD);
>>>>   }
>>>>   EXPORT_SYMBOL_GPL(coresight_trace_id_get_system_id);
>>>> +int coresight_trace_id_get_static_system_id(int trace_id)
>>>> +{
>>>> +    return coresight_trace_id_map_get_system_id(&id_map_default,
>>>> +            trace_id, TRACE_ID_REQ_STATIC);
>>>> +}
>>>> +EXPORT_SYMBOL_GPL(coresight_trace_id_get_static_system_id);
>>>> +
>>>>   void coresight_trace_id_put_system_id(int id)
>>>>   {
>>>>       coresight_trace_id_map_put_system_id(&id_map_default, id);
>>>> diff --git a/drivers/hwtracing/coresight/coresight-trace-id.h b/ 
>>>> drivers/hwtracing/coresight/coresight-trace-id.h
>>>> index 3797777d367e..ca2fdf31c835 100644
>>>> --- a/drivers/hwtracing/coresight/coresight-trace-id.h
>>>> +++ b/drivers/hwtracing/coresight/coresight-trace-id.h
>>>> @@ -122,6 +122,15 @@ int coresight_trace_id_read_cpu_id(int cpu);
>>>>    */
>>>>   int coresight_trace_id_get_system_id(void);
>>>> +/**
>>>> + * Allocate a CoreSight static trace ID for a system component.
>>>> + *
>>>> + * Used to allocate static IDs for system trace sources such as 
>>>> dummy source.
>>>> + *
>>>> + * return: Trace ID or -EINVAL if allocation is impossible.
>>>> + */
>>>> +int coresight_trace_id_get_static_system_id(int id);
>>>> +
>>>>   /**
>>>>    * Release an allocated system trace ID.
>>>>    *
>>>> diff --git a/include/linux/coresight.h b/include/linux/coresight.h
>>>> index f09ace92176e..2cdc0b1cd536 100644
>>>> --- a/include/linux/coresight.h
>>>> +++ b/include/linux/coresight.h
>>>> @@ -643,6 +643,7 @@ void coresight_relaxed_write64(struct 
>>>> coresight_device *csdev,
>>>>   void coresight_write64(struct coresight_device *csdev, u64 val, 
>>>> u32 offset);
>>>>   extern int coresight_get_cpu(struct device *dev);
>>>> +extern int coresight_get_static_trace_id(struct device *dev, u32 *id);
>>>>   struct coresight_platform_data *coresight_get_platform_data(struct 
>>>> device *dev);
>>>>   struct coresight_connection *
>>>
>>
>