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[PATCH] acpi: Use access_width over register_width for system memory accesses

Jarred White posted 1 patch 2 years, 4 months ago 
drivers/acpi/cppc_acpi.c | 24 +++++++++++++++++++++---
1 file changed, 21 insertions(+), 3 deletions(-)
[PATCH] acpi: Use access_width over register_width for system memory accesses
Posted by Jarred White 2 years, 4 months ago 
To align with ACPI 6.3+, since bit_width can be any 8-bit value, we cannot
depend on it being always on a clean 8b boundary. Instead, use access_width
to determine the size and use the offset and width to shift and mask the
bit swe want to read/write out. Make sure to add a check for system memory
since pcc redefines the access_width to subspace id.

Signed-off-by: Jarred White <jarredwhite@linux.microsoft.com>
---
 drivers/acpi/cppc_acpi.c | 24 +++++++++++++++++++++---
 1 file changed, 21 insertions(+), 3 deletions(-)

diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c
index 7ff269a78c20..07619b36c056 100644
--- a/drivers/acpi/cppc_acpi.c
+++ b/drivers/acpi/cppc_acpi.c
@@ -777,6 +777,7 @@ int acpi_cppc_processor_probe(struct acpi_processor *pr)
 			} else if (gas_t->space_id == ACPI_ADR_SPACE_SYSTEM_MEMORY) {
 				if (gas_t->address) {
 					void __iomem *addr;
+					size_t access_width;
 
 					if (!osc_cpc_flexible_adr_space_confirmed) {
 						pr_debug("Flexible address space capability not supported\n");
@@ -784,7 +785,8 @@ int acpi_cppc_processor_probe(struct acpi_processor *pr)
 							goto out_free;
 					}
 
-					addr = ioremap(gas_t->address, gas_t->bit_width/8);
+					access_width = ((8 << (gas_t->access_width - 1)) / 8);
+					addr = ioremap(gas_t->address, access_width);
 					if (!addr)
 						goto out_free;
 					cpc_ptr->cpc_regs[i-2].sys_mem_vaddr = addr;
@@ -980,6 +982,7 @@ int __weak cpc_write_ffh(int cpunum, struct cpc_reg *reg, u64 val)
 static int cpc_read(int cpu, struct cpc_register_resource *reg_res, u64 *val)
 {
 	void __iomem *vaddr = NULL;
+	int size;
 	int pcc_ss_id = per_cpu(cpu_pcc_subspace_idx, cpu);
 	struct cpc_reg *reg = &reg_res->cpc_entry.reg;
 
@@ -1015,7 +1018,12 @@ static int cpc_read(int cpu, struct cpc_register_resource *reg_res, u64 *val)
 		return acpi_os_read_memory((acpi_physical_address)reg->address,
 				val, reg->bit_width);
 
-	switch (reg->bit_width) {
+	if (reg->space_id == ACPI_ADR_SPACE_SYSTEM_MEMORY)
+		size = (8 << (reg->access_width - 1));
+	else
+		size = reg->bit_width;
+
+	switch (size) {
 	case 8:
 		*val = readb_relaxed(vaddr);
 		break;
@@ -1034,12 +1042,16 @@ static int cpc_read(int cpu, struct cpc_register_resource *reg_res, u64 *val)
 		return -EFAULT;
 	}
 
+	if (reg->space_id == ACPI_ADR_SPACE_SYSTEM_MEMORY)
+		*val = (*val >> reg->bit_offset) & GENMASK((reg->bit_width) - 1, 0);
+
 	return 0;
 }
 
 static int cpc_write(int cpu, struct cpc_register_resource *reg_res, u64 val)
 {
 	int ret_val = 0;
+	int size;
 	void __iomem *vaddr = NULL;
 	int pcc_ss_id = per_cpu(cpu_pcc_subspace_idx, cpu);
 	struct cpc_reg *reg = &reg_res->cpc_entry.reg;
@@ -1067,7 +1079,13 @@ static int cpc_write(int cpu, struct cpc_register_resource *reg_res, u64 val)
 		return acpi_os_write_memory((acpi_physical_address)reg->address,
 				val, reg->bit_width);
 
-	switch (reg->bit_width) {
+	if (reg->space_id == ACPI_ADR_SPACE_SYSTEM_MEMORY) {
+		size = (8 << (reg->access_width - 1));
+		val = (val >> reg->bit_offset) & GENMASK((reg->bit_width) - 1, 0);
+	} else
+		size = reg->bit_width;
+
+	switch (size) {
 	case 8:
 		writeb_relaxed(val, vaddr);
 		break;
-- 
2.34.1
Re: [PATCH] acpi: Use access_width over register_width for system memory accesses
Posted by Rafael J. Wysocki 2 years, 4 months ago 
On Mon, Sep 25, 2023 at 8:06 PM Jarred White
<jarredwhite@linux.microsoft.com> wrote:
>
> To align with ACPI 6.3+, since bit_width can be any 8-bit value, we cannot
> depend on it being always on a clean 8b boundary. Instead, use access_width
> to determine the size and use the offset and width to shift and mask the
> bit swe want to read/write out. Make sure to add a check for system memory
> since pcc redefines the access_width to subspace id.

This is fine, but what if there are systems in the field where
bit_width is invalid, but they just happen to work because of the way
it is currently handled?

> Signed-off-by: Jarred White <jarredwhite@linux.microsoft.com>
> ---
>  drivers/acpi/cppc_acpi.c | 24 +++++++++++++++++++++---
>  1 file changed, 21 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c
> index 7ff269a78c20..07619b36c056 100644
> --- a/drivers/acpi/cppc_acpi.c
> +++ b/drivers/acpi/cppc_acpi.c
> @@ -777,6 +777,7 @@ int acpi_cppc_processor_probe(struct acpi_processor *pr)
>                         } else if (gas_t->space_id == ACPI_ADR_SPACE_SYSTEM_MEMORY) {
>                                 if (gas_t->address) {
>                                         void __iomem *addr;
> +                                       size_t access_width;
>
>                                         if (!osc_cpc_flexible_adr_space_confirmed) {
>                                                 pr_debug("Flexible address space capability not supported\n");
> @@ -784,7 +785,8 @@ int acpi_cppc_processor_probe(struct acpi_processor *pr)
>                                                         goto out_free;
>                                         }
>
> -                                       addr = ioremap(gas_t->address, gas_t->bit_width/8);
> +                                       access_width = ((8 << (gas_t->access_width - 1)) / 8);

The 8 << (gas_t->access_width - 1) is duplicated twice below.  There
could be an inline function doing that computation.

And the outer parens above are not needed AFAICS.

> +                                       addr = ioremap(gas_t->address, access_width);
>                                         if (!addr)
>                                                 goto out_free;
>                                         cpc_ptr->cpc_regs[i-2].sys_mem_vaddr = addr;
> @@ -980,6 +982,7 @@ int __weak cpc_write_ffh(int cpunum, struct cpc_reg *reg, u64 val)
>  static int cpc_read(int cpu, struct cpc_register_resource *reg_res, u64 *val)
>  {
>         void __iomem *vaddr = NULL;
> +       int size;
>         int pcc_ss_id = per_cpu(cpu_pcc_subspace_idx, cpu);
>         struct cpc_reg *reg = &reg_res->cpc_entry.reg;
>
> @@ -1015,7 +1018,12 @@ static int cpc_read(int cpu, struct cpc_register_resource *reg_res, u64 *val)
>                 return acpi_os_read_memory((acpi_physical_address)reg->address,
>                                 val, reg->bit_width);
>
> -       switch (reg->bit_width) {
> +       if (reg->space_id == ACPI_ADR_SPACE_SYSTEM_MEMORY)
> +               size = (8 << (reg->access_width - 1));

Code duplication, outer perens not needed.

> +       else
> +               size = reg->bit_width;
> +
> +       switch (size) {
>         case 8:
>                 *val = readb_relaxed(vaddr);
>                 break;
> @@ -1034,12 +1042,16 @@ static int cpc_read(int cpu, struct cpc_register_resource *reg_res, u64 *val)
>                 return -EFAULT;
>         }
>
> +       if (reg->space_id == ACPI_ADR_SPACE_SYSTEM_MEMORY)
> +               *val = (*val >> reg->bit_offset) & GENMASK((reg->bit_width) - 1, 0);

The formula on the right-hand side of this is duplicated below.
Again, there could be an inline function doing this.

> +
>         return 0;
>  }
>
>  static int cpc_write(int cpu, struct cpc_register_resource *reg_res, u64 val)
>  {
>         int ret_val = 0;
> +       int size;
>         void __iomem *vaddr = NULL;
>         int pcc_ss_id = per_cpu(cpu_pcc_subspace_idx, cpu);
>         struct cpc_reg *reg = &reg_res->cpc_entry.reg;
> @@ -1067,7 +1079,13 @@ static int cpc_write(int cpu, struct cpc_register_resource *reg_res, u64 val)
>                 return acpi_os_write_memory((acpi_physical_address)reg->address,
>                                 val, reg->bit_width);
>
> -       switch (reg->bit_width) {
> +       if (reg->space_id == ACPI_ADR_SPACE_SYSTEM_MEMORY) {
> +               size = (8 << (reg->access_width - 1));
> +               val = (val >> reg->bit_offset) & GENMASK((reg->bit_width) - 1, 0);
> +       } else
> +               size = reg->bit_width;

Missing braces (as per the kernel coding style).

> +
> +       switch (size) {
>         case 8:
>                 writeb_relaxed(val, vaddr);
>                 break;
> --
> 2.34.1
>
Re: [PATCH] acpi: Use access_width over register_width for system memory accesses
Posted by Jarred White 2 years, 4 months ago 
On 10/3/2023 11:50 AM, Rafael J. Wysocki wrote:
 > On Mon, Sep 25, 2023 at 8:06 PM Jarred White
 > <jarredwhite@linux.microsoft.com> wrote:
 >> To align with ACPI 6.3+, since bit_width can be any 8-bit value, we 
cannot
 >> depend on it being always on a clean 8b boundary. Instead, use 
access_width
 >> to determine the size and use the offset and width to shift and mask the
 >> bit swe want to read/write out. Make sure to add a check for system 
memory
 >> since pcc redefines the access_width to subspace id.
 > This is fine, but what if there are systems in the field where
 > bit_width is invalid, but they just happen to work because of the way
 > it is currently handled?
For the kernel coding style issues, I will clean up for the v2 patch.

On the invalid bit_width for systems out there in the field, do you have 
any suggestions on how to handle this particular scenario? Would it be 
appropriate to add a kernel parameter flag that can revert back to the 
previous implementation?

P.S. Sorry for the HTML email.


Thanks,
Jarred
[PATCH v2] acpi: Use access_width over register_width for system memory accesses
Posted by Jarred White 2 years, 3 months ago 
To align with ACPI 6.3+, since bit_width can be any 8-bit value, we cannot
depend on it being always on a clean 8b boundary. Instead, use access_width
to determine the size and use the offset and width to shift and mask the
bits we want to read/write out. Make sure to add a check for system memory
since pcc redefines the access_width to subspace id.

Signed-off-by: Jarred White <jarredwhite@linux.microsoft.com>
---
changelog:
v1-->v2:
	1. Fixed coding style errors
        2. Backwards compatibility with ioremapping of address still an
           open question. Suggestions are welcomed.

 drivers/acpi/cppc_acpi.c | 36 +++++++++++++++++++++++++++++++-----
 1 file changed, 31 insertions(+), 5 deletions(-)

diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c
index 7ff269a78c20..fb37e1727bf8 100644
--- a/drivers/acpi/cppc_acpi.c
+++ b/drivers/acpi/cppc_acpi.c
@@ -163,6 +163,13 @@ show_cppc_data(cppc_get_perf_caps, cppc_perf_caps, nominal_freq);
 show_cppc_data(cppc_get_perf_ctrs, cppc_perf_fb_ctrs, reference_perf);
 show_cppc_data(cppc_get_perf_ctrs, cppc_perf_fb_ctrs, wraparound_time);
 
+/* Use access_width to determine the total number of bits */
+#define ACCESS_WIDTH_TO_BITS(reg) 8 << ((reg)->access_width - 1)
+
+/* Shift and apply the mask for CPC reads/writes */
+#define MASK_VAL(val) (((val) >> reg->bit_offset) & 			\
+					GENMASK((reg->bit_width), 0))
+
 static ssize_t show_feedback_ctrs(struct kobject *kobj,
 		struct kobj_attribute *attr, char *buf)
 {
@@ -777,6 +784,7 @@ int acpi_cppc_processor_probe(struct acpi_processor *pr)
 			} else if (gas_t->space_id == ACPI_ADR_SPACE_SYSTEM_MEMORY) {
 				if (gas_t->address) {
 					void __iomem *addr;
+					size_t access_width;
 
 					if (!osc_cpc_flexible_adr_space_confirmed) {
 						pr_debug("Flexible address space capability not supported\n");
@@ -784,7 +792,8 @@ int acpi_cppc_processor_probe(struct acpi_processor *pr)
 							goto out_free;
 					}
 
-					addr = ioremap(gas_t->address, gas_t->bit_width/8);
+					access_width = ACCESS_WIDTH_TO_BITS(gas_t) / 8;
+					addr = ioremap(gas_t->address, access_width);
 					if (!addr)
 						goto out_free;
 					cpc_ptr->cpc_regs[i-2].sys_mem_vaddr = addr;
@@ -980,6 +989,7 @@ int __weak cpc_write_ffh(int cpunum, struct cpc_reg *reg, u64 val)
 static int cpc_read(int cpu, struct cpc_register_resource *reg_res, u64 *val)
 {
 	void __iomem *vaddr = NULL;
+	int size;
 	int pcc_ss_id = per_cpu(cpu_pcc_subspace_idx, cpu);
 	struct cpc_reg *reg = &reg_res->cpc_entry.reg;
 
@@ -991,7 +1001,7 @@ static int cpc_read(int cpu, struct cpc_register_resource *reg_res, u64 *val)
 	*val = 0;
 
 	if (reg->space_id == ACPI_ADR_SPACE_SYSTEM_IO) {
-		u32 width = 8 << (reg->access_width - 1);
+		u32 width = ACCESS_WIDTH_TO_BITS(reg);
 		u32 val_u32;
 		acpi_status status;
 
@@ -1015,7 +1025,12 @@ static int cpc_read(int cpu, struct cpc_register_resource *reg_res, u64 *val)
 		return acpi_os_read_memory((acpi_physical_address)reg->address,
 				val, reg->bit_width);
 
-	switch (reg->bit_width) {
+	if (reg->space_id == ACPI_ADR_SPACE_SYSTEM_MEMORY)
+		size = ACCESS_WIDTH_TO_BITS(reg);
+	else
+		size = reg->bit_width;
+
+	switch (size) {
 	case 8:
 		*val = readb_relaxed(vaddr);
 		break;
@@ -1034,18 +1049,22 @@ static int cpc_read(int cpu, struct cpc_register_resource *reg_res, u64 *val)
 		return -EFAULT;
 	}
 
+	if (reg->space_id == ACPI_ADR_SPACE_SYSTEM_MEMORY)
+		*val = MASK_VAL(*val);
+
 	return 0;
 }
 
 static int cpc_write(int cpu, struct cpc_register_resource *reg_res, u64 val)
 {
 	int ret_val = 0;
+	int size;
 	void __iomem *vaddr = NULL;
 	int pcc_ss_id = per_cpu(cpu_pcc_subspace_idx, cpu);
 	struct cpc_reg *reg = &reg_res->cpc_entry.reg;
 
 	if (reg->space_id == ACPI_ADR_SPACE_SYSTEM_IO) {
-		u32 width = 8 << (reg->access_width - 1);
+		u32 width = ACCESS_WIDTH_TO_BITS(reg);
 		acpi_status status;
 
 		status = acpi_os_write_port((acpi_io_address)reg->address,
@@ -1067,7 +1086,14 @@ static int cpc_write(int cpu, struct cpc_register_resource *reg_res, u64 val)
 		return acpi_os_write_memory((acpi_physical_address)reg->address,
 				val, reg->bit_width);
 
-	switch (reg->bit_width) {
+	if (reg->space_id == ACPI_ADR_SPACE_SYSTEM_MEMORY) {
+		size = ACCESS_WIDTH_TO_BITS(reg);
+		val = MASK_VAL(val);
+	} else {
+		size = reg->bit_width;
+	}
+
+	switch (size) {
 	case 8:
 		writeb_relaxed(val, vaddr);
 		break;
-- 
2.34.1
Re: [PATCH v2] acpi: Use access_width over register_width for system memory accesses
Posted by Jarred White 2 years, 2 months ago 
Hello,

On 10/26/2023 2:15 PM, Jarred White wrote:
> To align with ACPI 6.3+, since bit_width can be any 8-bit value, we cannot
> depend on it being always on a clean 8b boundary. Instead, use access_width
> to determine the size and use the offset and width to shift and mask the
> bits we want to read/write out. Make sure to add a check for system memory
> since pcc redefines the access_width to subspace id.
> 
> Signed-off-by: Jarred White <jarredwhite@linux.microsoft.com>
> ---
> changelog:
> v1-->v2:
> 	1. Fixed coding style errors
>          2. Backwards compatibility with ioremapping of address still an
>             open question. Suggestions are welcomed.
> 
>   drivers/acpi/cppc_acpi.c | 36 +++++++++++++++++++++++++++++++-----
>   1 file changed, 31 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c
> index 7ff269a78c20..fb37e1727bf8 100644
> --- a/drivers/acpi/cppc_acpi.c
> +++ b/drivers/acpi/cppc_acpi.c
> @@ -163,6 +163,13 @@ show_cppc_data(cppc_get_perf_caps, cppc_perf_caps, nominal_freq);
>   show_cppc_data(cppc_get_perf_ctrs, cppc_perf_fb_ctrs, reference_perf);
>   show_cppc_data(cppc_get_perf_ctrs, cppc_perf_fb_ctrs, wraparound_time);
>   
> +/* Use access_width to determine the total number of bits */
> +#define ACCESS_WIDTH_TO_BITS(reg) 8 << ((reg)->access_width - 1)
> +
> +/* Shift and apply the mask for CPC reads/writes */
> +#define MASK_VAL(val) (((val) >> reg->bit_offset) & 			\
> +					GENMASK((reg->bit_width), 0))
> +
>   static ssize_t show_feedback_ctrs(struct kobject *kobj,
>   		struct kobj_attribute *attr, char *buf)
>   {
> @@ -777,6 +784,7 @@ int acpi_cppc_processor_probe(struct acpi_processor *pr)
>   			} else if (gas_t->space_id == ACPI_ADR_SPACE_SYSTEM_MEMORY) {
>   				if (gas_t->address) {
>   					void __iomem *addr;
> +					size_t access_width;
>   
>   					if (!osc_cpc_flexible_adr_space_confirmed) {
>   						pr_debug("Flexible address space capability not supported\n");
> @@ -784,7 +792,8 @@ int acpi_cppc_processor_probe(struct acpi_processor *pr)
>   							goto out_free;
>   					}
>   
> -					addr = ioremap(gas_t->address, gas_t->bit_width/8);
> +					access_width = ACCESS_WIDTH_TO_BITS(gas_t) / 8;
> +					addr = ioremap(gas_t->address, access_width);
>   					if (!addr)
>   						goto out_free;
>   					cpc_ptr->cpc_regs[i-2].sys_mem_vaddr = addr;
> @@ -980,6 +989,7 @@ int __weak cpc_write_ffh(int cpunum, struct cpc_reg *reg, u64 val)
>   static int cpc_read(int cpu, struct cpc_register_resource *reg_res, u64 *val)
>   {
>   	void __iomem *vaddr = NULL;
> +	int size;
>   	int pcc_ss_id = per_cpu(cpu_pcc_subspace_idx, cpu);
>   	struct cpc_reg *reg = &reg_res->cpc_entry.reg;
>   
> @@ -991,7 +1001,7 @@ static int cpc_read(int cpu, struct cpc_register_resource *reg_res, u64 *val)
>   	*val = 0;
>   
>   	if (reg->space_id == ACPI_ADR_SPACE_SYSTEM_IO) {
> -		u32 width = 8 << (reg->access_width - 1);
> +		u32 width = ACCESS_WIDTH_TO_BITS(reg);
>   		u32 val_u32;
>   		acpi_status status;
>   
> @@ -1015,7 +1025,12 @@ static int cpc_read(int cpu, struct cpc_register_resource *reg_res, u64 *val)
>   		return acpi_os_read_memory((acpi_physical_address)reg->address,
>   				val, reg->bit_width);
>   
> -	switch (reg->bit_width) {
> +	if (reg->space_id == ACPI_ADR_SPACE_SYSTEM_MEMORY)
> +		size = ACCESS_WIDTH_TO_BITS(reg);
> +	else
> +		size = reg->bit_width;
> +
> +	switch (size) {
>   	case 8:
>   		*val = readb_relaxed(vaddr);
>   		break;
> @@ -1034,18 +1049,22 @@ static int cpc_read(int cpu, struct cpc_register_resource *reg_res, u64 *val)
>   		return -EFAULT;
>   	}
>   
> +	if (reg->space_id == ACPI_ADR_SPACE_SYSTEM_MEMORY)
> +		*val = MASK_VAL(*val);
> +
>   	return 0;
>   }
>   
>   static int cpc_write(int cpu, struct cpc_register_resource *reg_res, u64 val)
>   {
>   	int ret_val = 0;
> +	int size;
>   	void __iomem *vaddr = NULL;
>   	int pcc_ss_id = per_cpu(cpu_pcc_subspace_idx, cpu);
>   	struct cpc_reg *reg = &reg_res->cpc_entry.reg;
>   
>   	if (reg->space_id == ACPI_ADR_SPACE_SYSTEM_IO) {
> -		u32 width = 8 << (reg->access_width - 1);
> +		u32 width = ACCESS_WIDTH_TO_BITS(reg);
>   		acpi_status status;
>   
>   		status = acpi_os_write_port((acpi_io_address)reg->address,
> @@ -1067,7 +1086,14 @@ static int cpc_write(int cpu, struct cpc_register_resource *reg_res, u64 val)
>   		return acpi_os_write_memory((acpi_physical_address)reg->address,
>   				val, reg->bit_width);
>   
> -	switch (reg->bit_width) {
> +	if (reg->space_id == ACPI_ADR_SPACE_SYSTEM_MEMORY) {
> +		size = ACCESS_WIDTH_TO_BITS(reg);
> +		val = MASK_VAL(val);
> +	} else {
> +		size = reg->bit_width;
> +	}
> +
> +	switch (size) {
>   	case 8:
>   		writeb_relaxed(val, vaddr);
>   		break;

I just wanted to follow-up on the V2 patch and discuss the open we have 
regarding the backwards compatibility with ioremapping of the address.


Thanks,
Jarred

Patchew 2.1-devel-b67e4c2

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