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[PATCH 4/7] coresight: Add claim tag warnings and debug messages

James Clark posted 7 patches 10 months, 1 week ago
There is a newer version of this series
[PATCH 4/7] coresight: Add claim tag warnings and debug messages
Posted by James Clark 10 months, 1 week ago 
Add a dev_dbg() message so that external debugger conflicts are more
visible. There are multiple reasons for -EBUSY so a message for this
particular one could be helpful. Add errors for and enumerate all the
other cases that are impossible.

Signed-off-by: James Clark <james.clark@linaro.org>
---
 drivers/hwtracing/coresight/coresight-core.c | 48 ++++++++++++--------
 drivers/hwtracing/coresight/coresight-priv.h |  5 +-
 2 files changed, 34 insertions(+), 19 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-core.c b/drivers/hwtracing/coresight/coresight-core.c
index 7b53165c93af..7fe5d5d432c4 100644
--- a/drivers/hwtracing/coresight/coresight-core.c
+++ b/drivers/hwtracing/coresight/coresight-core.c
@@ -133,16 +133,6 @@ static inline u32 coresight_read_claim_tags(struct csdev_access *csa)
 			 csdev_access_relaxed_read32(csa, CORESIGHT_CLAIMCLR));
 }
 
-static inline bool coresight_is_claimed_self_hosted(struct csdev_access *csa)
-{
-	return coresight_read_claim_tags(csa) == CORESIGHT_CLAIM_SELF_HOSTED;
-}
-
-static inline bool coresight_is_claimed_any(struct coresight_device *csdev)
-{
-	return coresight_read_claim_tags(&csdev->access) != 0;
-}
-
 static inline void coresight_set_self_claim_tag(struct csdev_access *csa)
 {
 	csdev_access_relaxed_write32(csa, CORESIGHT_CLAIM_SELF_HOSTED,
@@ -169,18 +159,40 @@ static inline void coresight_clear_self_claim_tag(struct csdev_access *csa)
  */
 int coresight_claim_device_unlocked(struct coresight_device *csdev)
 {
+	int tag;
+	struct csdev_access *csa;
+
 	if (WARN_ON(!csdev))
 		return -EINVAL;
 
-	if (coresight_is_claimed_any(csdev))
+	csa = &csdev->access;
+	tag = coresight_read_claim_tags(csa);
+
+	switch (tag) {
+	case CORESIGHT_CLAIM_FREE:
+		coresight_set_self_claim_tag(csa);
+		if (coresight_read_claim_tags(csa) == CORESIGHT_CLAIM_SELF_HOSTED)
+			return 0;
+
+		/* There was a race setting the tag, clean up and fail */
+		coresight_clear_self_claim_tag(csa);
 		return -EBUSY;
 
-	coresight_set_self_claim_tag(&csdev->access);
-	if (coresight_is_claimed_self_hosted(&csdev->access))
-		return 0;
-	/* There was a race setting the tag, clean up and fail */
-	coresight_clear_self_claim_tag(&csdev->access);
-	return -EBUSY;
+	case CORESIGHT_CLAIM_EXTERNAL:
+		/* External debug is an expected state, so log and report BUSY */
+		dev_dbg(&csdev->dev, "Busy: Claimed by external debugger");
+		return -EBUSY;
+
+	default:
+	case CORESIGHT_CLAIM_SELF_HOSTED:
+	case CORESIGHT_CLAIM_INVALID:
+		/*
+		 * Warn here because we clear a lingering self hosted tag
+		 * on probe, so other tag combinations are impossible.
+		 */
+		dev_err_once(&csdev->dev, "Invalid claim tag state: %x", tag);
+		return -EBUSY;
+	}
 }
 EXPORT_SYMBOL_GPL(coresight_claim_device_unlocked);
 
@@ -205,7 +217,7 @@ EXPORT_SYMBOL_GPL(coresight_claim_device);
  */
 void coresight_disclaim_device_unlocked(struct csdev_access *csa)
 {
-	if (coresight_is_claimed_self_hosted(csa))
+	if (coresight_read_claim_tags(csa) == CORESIGHT_CLAIM_SELF_HOSTED)
 		coresight_clear_self_claim_tag(csa);
 	else
 		/*
diff --git a/drivers/hwtracing/coresight/coresight-priv.h b/drivers/hwtracing/coresight/coresight-priv.h
index cc7ff1e36ef4..a83113225797 100644
--- a/drivers/hwtracing/coresight/coresight-priv.h
+++ b/drivers/hwtracing/coresight/coresight-priv.h
@@ -36,7 +36,10 @@ extern const struct device_type coresight_dev_type[];
  * See PSCI - ARM DEN 0022D, Section: 6.8.1 Debug and Trace save and restore.
  */
 #define CORESIGHT_CLAIM_MASK		GENMASK(1, 0)
-#define CORESIGHT_CLAIM_SELF_HOSTED	BIT(1)
+#define CORESIGHT_CLAIM_FREE		0
+#define CORESIGHT_CLAIM_EXTERNAL	1
+#define CORESIGHT_CLAIM_SELF_HOSTED	2
+#define CORESIGHT_CLAIM_INVALID		3
 
 #define TIMEOUT_US		100
 #define BMVAL(val, lsb, msb)	((val & GENMASK(msb, lsb)) >> lsb)
-- 
2.34.1
Re: [PATCH 4/7] coresight: Add claim tag warnings and debug messages
Posted by Leo Yan 9 months, 1 week ago 
On Tue, Feb 11, 2025 at 10:39:40AM +0000, James Clark wrote:
> 
> Add a dev_dbg() message so that external debugger conflicts are more
> visible. There are multiple reasons for -EBUSY so a message for this
> particular one could be helpful. Add errors for and enumerate all the
> other cases that are impossible.
> 
> Signed-off-by: James Clark <james.clark@linaro.org>
> ---
>  drivers/hwtracing/coresight/coresight-core.c | 48 ++++++++++++--------
>  drivers/hwtracing/coresight/coresight-priv.h |  5 +-
>  2 files changed, 34 insertions(+), 19 deletions(-)
> 
> diff --git a/drivers/hwtracing/coresight/coresight-core.c b/drivers/hwtracing/coresight/coresight-core.c
> index 7b53165c93af..7fe5d5d432c4 100644
> --- a/drivers/hwtracing/coresight/coresight-core.c
> +++ b/drivers/hwtracing/coresight/coresight-core.c
> @@ -133,16 +133,6 @@ static inline u32 coresight_read_claim_tags(struct csdev_access *csa)
>                          csdev_access_relaxed_read32(csa, CORESIGHT_CLAIMCLR));
>  }
> 
> -static inline bool coresight_is_claimed_self_hosted(struct csdev_access *csa)
> -{
> -       return coresight_read_claim_tags(csa) == CORESIGHT_CLAIM_SELF_HOSTED;
> -}
> -
> -static inline bool coresight_is_claimed_any(struct coresight_device *csdev)
> -{
> -       return coresight_read_claim_tags(&csdev->access) != 0;
> -}
> -
>  static inline void coresight_set_self_claim_tag(struct csdev_access *csa)
>  {
>         csdev_access_relaxed_write32(csa, CORESIGHT_CLAIM_SELF_HOSTED,
> @@ -169,18 +159,40 @@ static inline void coresight_clear_self_claim_tag(struct csdev_access *csa)
>   */
>  int coresight_claim_device_unlocked(struct coresight_device *csdev)
>  {
> +       int tag;
> +       struct csdev_access *csa;
> +
>         if (WARN_ON(!csdev))
>                 return -EINVAL;
> 
> -       if (coresight_is_claimed_any(csdev))
> +       csa = &csdev->access;
> +       tag = coresight_read_claim_tags(csa);
> +
> +       switch (tag) {
> +       case CORESIGHT_CLAIM_FREE:
> +               coresight_set_self_claim_tag(csa);
> +               if (coresight_read_claim_tags(csa) == CORESIGHT_CLAIM_SELF_HOSTED)
> +                       return 0;
> +

It would be a rare case if a failure happens here.  Seems to me, it
would be valuable to print a log for this edge case.

Otherwise, looks good to me.

> +               /* There was a race setting the tag, clean up and fail */
> +               coresight_clear_self_claim_tag(csa);
>                 return -EBUSY;
> 
> -       coresight_set_self_claim_tag(&csdev->access);
> -       if (coresight_is_claimed_self_hosted(&csdev->access))
> -               return 0;
> -       /* There was a race setting the tag, clean up and fail */
> -       coresight_clear_self_claim_tag(&csdev->access);
> -       return -EBUSY;
> +       case CORESIGHT_CLAIM_EXTERNAL:
> +               /* External debug is an expected state, so log and report BUSY */
> +               dev_dbg(&csdev->dev, "Busy: Claimed by external debugger");
> +               return -EBUSY;
> +
> +       default:
> +       case CORESIGHT_CLAIM_SELF_HOSTED:
> +       case CORESIGHT_CLAIM_INVALID:
> +               /*
> +                * Warn here because we clear a lingering self hosted tag
> +                * on probe, so other tag combinations are impossible.
> +                */
> +               dev_err_once(&csdev->dev, "Invalid claim tag state: %x", tag);
> +               return -EBUSY;
> +       }
>  }
>  EXPORT_SYMBOL_GPL(coresight_claim_device_unlocked);
> 
> @@ -205,7 +217,7 @@ EXPORT_SYMBOL_GPL(coresight_claim_device);
>   */
>  void coresight_disclaim_device_unlocked(struct csdev_access *csa)
>  {
> -       if (coresight_is_claimed_self_hosted(csa))
> +       if (coresight_read_claim_tags(csa) == CORESIGHT_CLAIM_SELF_HOSTED)
>                 coresight_clear_self_claim_tag(csa);
>         else
>                 /*
> diff --git a/drivers/hwtracing/coresight/coresight-priv.h b/drivers/hwtracing/coresight/coresight-priv.h
> index cc7ff1e36ef4..a83113225797 100644
> --- a/drivers/hwtracing/coresight/coresight-priv.h
> +++ b/drivers/hwtracing/coresight/coresight-priv.h
> @@ -36,7 +36,10 @@ extern const struct device_type coresight_dev_type[];
>   * See PSCI - ARM DEN 0022D, Section: 6.8.1 Debug and Trace save and restore.
>   */
>  #define CORESIGHT_CLAIM_MASK           GENMASK(1, 0)
> -#define CORESIGHT_CLAIM_SELF_HOSTED    BIT(1)
> +#define CORESIGHT_CLAIM_FREE           0
> +#define CORESIGHT_CLAIM_EXTERNAL       1
> +#define CORESIGHT_CLAIM_SELF_HOSTED    2
> +#define CORESIGHT_CLAIM_INVALID                3
> 
>  #define TIMEOUT_US             100
>  #define BMVAL(val, lsb, msb)   ((val & GENMASK(msb, lsb)) >> lsb)
> --
> 2.34.1
> 
> _______________________________________________
> CoreSight mailing list -- coresight@lists.linaro.org
> To unsubscribe send an email to coresight-leave@lists.linaro.org
Re: [PATCH 4/7] coresight: Add claim tag warnings and debug messages
Posted by James Clark 9 months ago 

On 13/03/2025 2:40 pm, Leo Yan wrote:
> On Tue, Feb 11, 2025 at 10:39:40AM +0000, James Clark wrote:
>>
>> Add a dev_dbg() message so that external debugger conflicts are more
>> visible. There are multiple reasons for -EBUSY so a message for this
>> particular one could be helpful. Add errors for and enumerate all the
>> other cases that are impossible.
>>
>> Signed-off-by: James Clark <james.clark@linaro.org>
>> ---
>>   drivers/hwtracing/coresight/coresight-core.c | 48 ++++++++++++--------
>>   drivers/hwtracing/coresight/coresight-priv.h |  5 +-
>>   2 files changed, 34 insertions(+), 19 deletions(-)
>>
>> diff --git a/drivers/hwtracing/coresight/coresight-core.c b/drivers/hwtracing/coresight/coresight-core.c
>> index 7b53165c93af..7fe5d5d432c4 100644
>> --- a/drivers/hwtracing/coresight/coresight-core.c
>> +++ b/drivers/hwtracing/coresight/coresight-core.c
>> @@ -133,16 +133,6 @@ static inline u32 coresight_read_claim_tags(struct csdev_access *csa)
>>                           csdev_access_relaxed_read32(csa, CORESIGHT_CLAIMCLR));
>>   }
>>
>> -static inline bool coresight_is_claimed_self_hosted(struct csdev_access *csa)
>> -{
>> -       return coresight_read_claim_tags(csa) == CORESIGHT_CLAIM_SELF_HOSTED;
>> -}
>> -
>> -static inline bool coresight_is_claimed_any(struct coresight_device *csdev)
>> -{
>> -       return coresight_read_claim_tags(&csdev->access) != 0;
>> -}
>> -
>>   static inline void coresight_set_self_claim_tag(struct csdev_access *csa)
>>   {
>>          csdev_access_relaxed_write32(csa, CORESIGHT_CLAIM_SELF_HOSTED,
>> @@ -169,18 +159,40 @@ static inline void coresight_clear_self_claim_tag(struct csdev_access *csa)
>>    */
>>   int coresight_claim_device_unlocked(struct coresight_device *csdev)
>>   {
>> +       int tag;
>> +       struct csdev_access *csa;
>> +
>>          if (WARN_ON(!csdev))
>>                  return -EINVAL;
>>
>> -       if (coresight_is_claimed_any(csdev))
>> +       csa = &csdev->access;
>> +       tag = coresight_read_claim_tags(csa);
>> +
>> +       switch (tag) {
>> +       case CORESIGHT_CLAIM_FREE:
>> +               coresight_set_self_claim_tag(csa);
>> +               if (coresight_read_claim_tags(csa) == CORESIGHT_CLAIM_SELF_HOSTED)
>> +                       return 0;
>> +
> 
> It would be a rare case if a failure happens here.  Seems to me, it
> would be valuable to print a log for this edge case.
> 
> Otherwise, looks good to me.
> 

Yeah I can add dev_dbg("Busy: Couldn't set self claim tag"). Just to 
distinguish this race case from the other busy case.

Patchew 2.1-devel-b67e4c2

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