[PATCH v2 3/4] ACPI: CPPC: Do not use CPUFREQ_ETERNAL as an error value

Posted by Rafael J. Wysocki 2 months, 3 weeks ago

From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Instead of using CPUFREQ_ETERNAL for signaling an error condition
in cppc_get_transition_latency(), change the return value type of
that function to int and make it return a proper negative error
code on failures.

No intentional functional impact.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---

v1 -> v2:
   * Change cppc_get_transition_latency() return value data type to int
   * Make it return -ENODATA on errors (Mario)
   * Update its callers accordingly
   * Adjust the subject and changelog
   * Add a missing empty code line to cppc_get_transition_latency()

The modifications of this patch don't affect any other patches in the series:

https://lore.kernel.org/linux-pm/8605612.T7Z3S40VBb@rafael.j.wysocki/

---
 drivers/acpi/cppc_acpi.c       |   15 ++++++++-------
 drivers/cpufreq/amd-pstate.c   |    8 ++++----
 drivers/cpufreq/cppc_cpufreq.c |    4 ++--
 include/acpi/cppc_acpi.h       |    6 +++---
 4 files changed, 17 insertions(+), 16 deletions(-)

--- a/drivers/acpi/cppc_acpi.c
+++ b/drivers/acpi/cppc_acpi.c
@@ -1876,7 +1876,7 @@ EXPORT_SYMBOL_GPL(cppc_set_perf);
  * If desired_reg is in the SystemMemory or SystemIo ACPI address space,
  * then assume there is no latency.
  */
-unsigned int cppc_get_transition_latency(int cpu_num)
+int cppc_get_transition_latency(int cpu_num)
 {
 	/*
 	 * Expected transition latency is based on the PCCT timing values
@@ -1889,31 +1889,32 @@ unsigned int cppc_get_transition_latency
 	 *              completion of a command before issuing the next command,
 	 *              in microseconds.
 	 */
-	unsigned int latency_ns = 0;
 	struct cpc_desc *cpc_desc;
 	struct cpc_register_resource *desired_reg;
 	int pcc_ss_id = per_cpu(cpu_pcc_subspace_idx, cpu_num);
 	struct cppc_pcc_data *pcc_ss_data;
+	int latency_ns = 0;
 
 	cpc_desc = per_cpu(cpc_desc_ptr, cpu_num);
 	if (!cpc_desc)
-		return CPUFREQ_ETERNAL;
+		return -ENODATA;
 
 	desired_reg = &cpc_desc->cpc_regs[DESIRED_PERF];
 	if (CPC_IN_SYSTEM_MEMORY(desired_reg) || CPC_IN_SYSTEM_IO(desired_reg))
 		return 0;
+
 	else if (!CPC_IN_PCC(desired_reg))
-		return CPUFREQ_ETERNAL;
+		return -ENODATA;
 
 	if (pcc_ss_id < 0)
-		return CPUFREQ_ETERNAL;
+		return -ENODATA;
 
 	pcc_ss_data = pcc_data[pcc_ss_id];
 	if (pcc_ss_data->pcc_mpar)
 		latency_ns = 60 * (1000 * 1000 * 1000 / pcc_ss_data->pcc_mpar);
 
-	latency_ns = max(latency_ns, pcc_ss_data->pcc_nominal * 1000);
-	latency_ns = max(latency_ns, pcc_ss_data->pcc_mrtt * 1000);
+	latency_ns = max_t(int, latency_ns, pcc_ss_data->pcc_nominal * 1000);
+	latency_ns = max_t(int, latency_ns, pcc_ss_data->pcc_mrtt * 1000);
 
 	return latency_ns;
 }
--- a/drivers/cpufreq/amd-pstate.c
+++ b/drivers/cpufreq/amd-pstate.c
@@ -872,10 +872,10 @@ static void amd_pstate_update_limits(str
  */
 static u32 amd_pstate_get_transition_delay_us(unsigned int cpu)
 {
-	u32 transition_delay_ns;
+	int transition_delay_ns;
 
 	transition_delay_ns = cppc_get_transition_latency(cpu);
-	if (transition_delay_ns == CPUFREQ_ETERNAL) {
+	if (transition_delay_ns < 0) {
 		if (cpu_feature_enabled(X86_FEATURE_AMD_FAST_CPPC))
 			return AMD_PSTATE_FAST_CPPC_TRANSITION_DELAY;
 		else
@@ -891,10 +891,10 @@ static u32 amd_pstate_get_transition_del
  */
 static u32 amd_pstate_get_transition_latency(unsigned int cpu)
 {
-	u32 transition_latency;
+	int transition_latency;
 
 	transition_latency = cppc_get_transition_latency(cpu);
-	if (transition_latency  == CPUFREQ_ETERNAL)
+	if (transition_latency < 0)
 		return AMD_PSTATE_TRANSITION_LATENCY;
 
 	return transition_latency;
--- a/drivers/cpufreq/cppc_cpufreq.c
+++ b/drivers/cpufreq/cppc_cpufreq.c
@@ -310,9 +310,9 @@ static int cppc_verify_policy(struct cpu
 
 static unsigned int get_transition_latency_from_cppc(unsigned int cpu)
 {
-	unsigned int transition_latency_ns = cppc_get_transition_latency(cpu);
+	int transition_latency_ns = cppc_get_transition_latency(cpu);
 
-	if (transition_latency_ns == CPUFREQ_ETERNAL)
+	if (transition_latency_ns < 0)
 		return CPUFREQ_DEFAULT_TRANSITION_LATENCY_NS / NSEC_PER_USEC;
 
 	return transition_latency_ns / NSEC_PER_USEC;
--- a/include/acpi/cppc_acpi.h
+++ b/include/acpi/cppc_acpi.h
@@ -160,7 +160,7 @@ extern unsigned int cppc_khz_to_perf(str
 extern bool acpi_cpc_valid(void);
 extern bool cppc_allow_fast_switch(void);
 extern int acpi_get_psd_map(unsigned int cpu, struct cppc_cpudata *cpu_data);
-extern unsigned int cppc_get_transition_latency(int cpu);
+extern int cppc_get_transition_latency(int cpu);
 extern bool cpc_ffh_supported(void);
 extern bool cpc_supported_by_cpu(void);
 extern int cpc_read_ffh(int cpunum, struct cpc_reg *reg, u64 *val);
@@ -216,9 +216,9 @@ static inline bool cppc_allow_fast_switc
 {
 	return false;
 }
-static inline unsigned int cppc_get_transition_latency(int cpu)
+static inline int cppc_get_transition_latency(int cpu)
 {
-	return CPUFREQ_ETERNAL;
+	return -ENODATA;
 }
 static inline bool cpc_ffh_supported(void)
 {

Re: [PATCH v2 3/4] ACPI: CPPC: Do not use CPUFREQ_ETERNAL as an error value

Posted by Jie Zhan 2 months, 3 weeks ago


On 9/26/2025 1:23 AM, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> 
> Instead of using CPUFREQ_ETERNAL for signaling an error condition
> in cppc_get_transition_latency(), change the return value type of
> that function to int and make it return a proper negative error
> code on failures.
> 
> No intentional functional impact.
> 
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
A minor comment inline.  Other than that,
Reviewed-by: Jie Zhan <zhanjie9@hisilicon.com>
> ---
> 
> v1 -> v2:
>    * Change cppc_get_transition_latency() return value data type to int
>    * Make it return -ENODATA on errors (Mario)
>    * Update its callers accordingly
>    * Adjust the subject and changelog
>    * Add a missing empty code line to cppc_get_transition_latency()
> 
> The modifications of this patch don't affect any other patches in the series:
> 
> https://lore.kernel.org/linux-pm/8605612.T7Z3S40VBb@rafael.j.wysocki/
> 
> ---
>  drivers/acpi/cppc_acpi.c       |   15 ++++++++-------
>  drivers/cpufreq/amd-pstate.c   |    8 ++++----
>  drivers/cpufreq/cppc_cpufreq.c |    4 ++--
>  include/acpi/cppc_acpi.h       |    6 +++---
>  4 files changed, 17 insertions(+), 16 deletions(-)
> 
> --- a/drivers/acpi/cppc_acpi.c
> +++ b/drivers/acpi/cppc_acpi.c
> @@ -1876,7 +1876,7 @@ EXPORT_SYMBOL_GPL(cppc_set_perf);
>   * If desired_reg is in the SystemMemory or SystemIo ACPI address space,
>   * then assume there is no latency.
>   */
> -unsigned int cppc_get_transition_latency(int cpu_num)
> +int cppc_get_transition_latency(int cpu_num)
>  {
>  	/*
>  	 * Expected transition latency is based on the PCCT timing values
> @@ -1889,31 +1889,32 @@ unsigned int cppc_get_transition_latency
>  	 *              completion of a command before issuing the next command,
>  	 *              in microseconds.
>  	 */
> -	unsigned int latency_ns = 0;
>  	struct cpc_desc *cpc_desc;
>  	struct cpc_register_resource *desired_reg;
>  	int pcc_ss_id = per_cpu(cpu_pcc_subspace_idx, cpu_num);
>  	struct cppc_pcc_data *pcc_ss_data;
> +	int latency_ns = 0;
>  
>  	cpc_desc = per_cpu(cpc_desc_ptr, cpu_num);
>  	if (!cpc_desc)
> -		return CPUFREQ_ETERNAL;
> +		return -ENODATA;
>  
>  	desired_reg = &cpc_desc->cpc_regs[DESIRED_PERF];
>  	if (CPC_IN_SYSTEM_MEMORY(desired_reg) || CPC_IN_SYSTEM_IO(desired_reg))
>  		return 0;
> +
An extra line here.

Alternatively, can we cleanup a bit:

if (!CPC_IN_PCC(desired_reg) || pcc_ss_id < 0)
	return -ENODATA;

>  	else if (!CPC_IN_PCC(desired_reg))
> -		return CPUFREQ_ETERNAL;
> +		return -ENODATA;
>  
>  	if (pcc_ss_id < 0)
> -		return CPUFREQ_ETERNAL;
> +		return -ENODATA;
>  
>  	pcc_ss_data = pcc_data[pcc_ss_id];
>  	if (pcc_ss_data->pcc_mpar)
>  		latency_ns = 60 * (1000 * 1000 * 1000 / pcc_ss_data->pcc_mpar);
>  
> -	latency_ns = max(latency_ns, pcc_ss_data->pcc_nominal * 1000);
> -	latency_ns = max(latency_ns, pcc_ss_data->pcc_mrtt * 1000);
> +	latency_ns = max_t(int, latency_ns, pcc_ss_data->pcc_nominal * 1000);
> +	latency_ns = max_t(int, latency_ns, pcc_ss_data->pcc_mrtt * 1000);
>  
>  	return latency_ns;
>  }
> --- a/drivers/cpufreq/amd-pstate.c
> +++ b/drivers/cpufreq/amd-pstate.c
> @@ -872,10 +872,10 @@ static void amd_pstate_update_limits(str
>   */
>  static u32 amd_pstate_get_transition_delay_us(unsigned int cpu)
>  {
> -	u32 transition_delay_ns;
> +	int transition_delay_ns;
>  
>  	transition_delay_ns = cppc_get_transition_latency(cpu);
> -	if (transition_delay_ns == CPUFREQ_ETERNAL) {
> +	if (transition_delay_ns < 0) {
>  		if (cpu_feature_enabled(X86_FEATURE_AMD_FAST_CPPC))
>  			return AMD_PSTATE_FAST_CPPC_TRANSITION_DELAY;
>  		else
> @@ -891,10 +891,10 @@ static u32 amd_pstate_get_transition_del
>   */
>  static u32 amd_pstate_get_transition_latency(unsigned int cpu)
>  {
> -	u32 transition_latency;
> +	int transition_latency;
>  
>  	transition_latency = cppc_get_transition_latency(cpu);
> -	if (transition_latency  == CPUFREQ_ETERNAL)
> +	if (transition_latency < 0)
>  		return AMD_PSTATE_TRANSITION_LATENCY;
>  
>  	return transition_latency;
> --- a/drivers/cpufreq/cppc_cpufreq.c
> +++ b/drivers/cpufreq/cppc_cpufreq.c
> @@ -310,9 +310,9 @@ static int cppc_verify_policy(struct cpu
>  
>  static unsigned int get_transition_latency_from_cppc(unsigned int cpu)
>  {
> -	unsigned int transition_latency_ns = cppc_get_transition_latency(cpu);
> +	int transition_latency_ns = cppc_get_transition_latency(cpu);
>  
> -	if (transition_latency_ns == CPUFREQ_ETERNAL)
> +	if (transition_latency_ns < 0)
>  		return CPUFREQ_DEFAULT_TRANSITION_LATENCY_NS / NSEC_PER_USEC;
>  
>  	return transition_latency_ns / NSEC_PER_USEC;
> --- a/include/acpi/cppc_acpi.h
> +++ b/include/acpi/cppc_acpi.h
> @@ -160,7 +160,7 @@ extern unsigned int cppc_khz_to_perf(str
>  extern bool acpi_cpc_valid(void);
>  extern bool cppc_allow_fast_switch(void);
>  extern int acpi_get_psd_map(unsigned int cpu, struct cppc_cpudata *cpu_data);
> -extern unsigned int cppc_get_transition_latency(int cpu);
> +extern int cppc_get_transition_latency(int cpu);
>  extern bool cpc_ffh_supported(void);
>  extern bool cpc_supported_by_cpu(void);
>  extern int cpc_read_ffh(int cpunum, struct cpc_reg *reg, u64 *val);
> @@ -216,9 +216,9 @@ static inline bool cppc_allow_fast_switc
>  {
>  	return false;
>  }
> -static inline unsigned int cppc_get_transition_latency(int cpu)
> +static inline int cppc_get_transition_latency(int cpu)
>  {
> -	return CPUFREQ_ETERNAL;
> +	return -ENODATA;
>  }
>  static inline bool cpc_ffh_supported(void)
>  {
> 
> 
> 
>

Re: [PATCH v2 3/4] ACPI: CPPC: Do not use CPUFREQ_ETERNAL as an error value

Posted by Rafael J. Wysocki 2 months, 3 weeks ago

On Fri, Sep 26, 2025 at 11:30 AM Jie Zhan <zhanjie9@hisilicon.com> wrote:
>
>
>
> On 9/26/2025 1:23 AM, Rafael J. Wysocki wrote:
> > From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> >
> > Instead of using CPUFREQ_ETERNAL for signaling an error condition
> > in cppc_get_transition_latency(), change the return value type of
> > that function to int and make it return a proper negative error
> > code on failures.
> >
> > No intentional functional impact.
> >
> > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> A minor comment inline.  Other than that,
> Reviewed-by: Jie Zhan <zhanjie9@hisilicon.com>

Thanks!

> > ---
> >
> > v1 -> v2:
> >    * Change cppc_get_transition_latency() return value data type to int
> >    * Make it return -ENODATA on errors (Mario)
> >    * Update its callers accordingly
> >    * Adjust the subject and changelog
> >    * Add a missing empty code line to cppc_get_transition_latency()
> >
> > The modifications of this patch don't affect any other patches in the series:
> >
> > https://lore.kernel.org/linux-pm/8605612.T7Z3S40VBb@rafael.j.wysocki/
> >
> > ---
> >  drivers/acpi/cppc_acpi.c       |   15 ++++++++-------
> >  drivers/cpufreq/amd-pstate.c   |    8 ++++----
> >  drivers/cpufreq/cppc_cpufreq.c |    4 ++--
> >  include/acpi/cppc_acpi.h       |    6 +++---
> >  4 files changed, 17 insertions(+), 16 deletions(-)
> >
> > --- a/drivers/acpi/cppc_acpi.c
> > +++ b/drivers/acpi/cppc_acpi.c
> > @@ -1876,7 +1876,7 @@ EXPORT_SYMBOL_GPL(cppc_set_perf);
> >   * If desired_reg is in the SystemMemory or SystemIo ACPI address space,
> >   * then assume there is no latency.
> >   */
> > -unsigned int cppc_get_transition_latency(int cpu_num)
> > +int cppc_get_transition_latency(int cpu_num)
> >  {
> >       /*
> >        * Expected transition latency is based on the PCCT timing values
> > @@ -1889,31 +1889,32 @@ unsigned int cppc_get_transition_latency
> >        *              completion of a command before issuing the next command,
> >        *              in microseconds.
> >        */
> > -     unsigned int latency_ns = 0;
> >       struct cpc_desc *cpc_desc;
> >       struct cpc_register_resource *desired_reg;
> >       int pcc_ss_id = per_cpu(cpu_pcc_subspace_idx, cpu_num);
> >       struct cppc_pcc_data *pcc_ss_data;
> > +     int latency_ns = 0;
> >
> >       cpc_desc = per_cpu(cpc_desc_ptr, cpu_num);
> >       if (!cpc_desc)
> > -             return CPUFREQ_ETERNAL;
> > +             return -ENODATA;
> >
> >       desired_reg = &cpc_desc->cpc_regs[DESIRED_PERF];
> >       if (CPC_IN_SYSTEM_MEMORY(desired_reg) || CPC_IN_SYSTEM_IO(desired_reg))
> >               return 0;
> > +
> An extra line here.

Yes, and it is intentional (see the changes between v1 and v2).

> Alternatively, can we cleanup a bit:

That can be done.

> if (!CPC_IN_PCC(desired_reg) || pcc_ss_id < 0)
>         return -ENODATA;
>
> >       else if (!CPC_IN_PCC(desired_reg))
> > -             return CPUFREQ_ETERNAL;
> > +             return -ENODATA;
> >
> >       if (pcc_ss_id < 0)
> > -             return CPUFREQ_ETERNAL;
> > +             return -ENODATA;
> >
> >       pcc_ss_data = pcc_data[pcc_ss_id];
> >       if (pcc_ss_data->pcc_mpar)
> >               latency_ns = 60 * (1000 * 1000 * 1000 / pcc_ss_data->pcc_mpar);
> >
> > -     latency_ns = max(latency_ns, pcc_ss_data->pcc_nominal * 1000);
> > -     latency_ns = max(latency_ns, pcc_ss_data->pcc_mrtt * 1000);
> > +     latency_ns = max_t(int, latency_ns, pcc_ss_data->pcc_nominal * 1000);
> > +     latency_ns = max_t(int, latency_ns, pcc_ss_data->pcc_mrtt * 1000);
> >
> >       return latency_ns;
> >  }
> > --- a/drivers/cpufreq/amd-pstate.c
> > +++ b/drivers/cpufreq/amd-pstate.c
> > @@ -872,10 +872,10 @@ static void amd_pstate_update_limits(str
> >   */
> >  static u32 amd_pstate_get_transition_delay_us(unsigned int cpu)
> >  {
> > -     u32 transition_delay_ns;
> > +     int transition_delay_ns;
> >
> >       transition_delay_ns = cppc_get_transition_latency(cpu);
> > -     if (transition_delay_ns == CPUFREQ_ETERNAL) {
> > +     if (transition_delay_ns < 0) {
> >               if (cpu_feature_enabled(X86_FEATURE_AMD_FAST_CPPC))
> >                       return AMD_PSTATE_FAST_CPPC_TRANSITION_DELAY;
> >               else
> > @@ -891,10 +891,10 @@ static u32 amd_pstate_get_transition_del
> >   */
> >  static u32 amd_pstate_get_transition_latency(unsigned int cpu)
> >  {
> > -     u32 transition_latency;
> > +     int transition_latency;
> >
> >       transition_latency = cppc_get_transition_latency(cpu);
> > -     if (transition_latency  == CPUFREQ_ETERNAL)
> > +     if (transition_latency < 0)
> >               return AMD_PSTATE_TRANSITION_LATENCY;
> >
> >       return transition_latency;
> > --- a/drivers/cpufreq/cppc_cpufreq.c
> > +++ b/drivers/cpufreq/cppc_cpufreq.c
> > @@ -310,9 +310,9 @@ static int cppc_verify_policy(struct cpu
> >
> >  static unsigned int get_transition_latency_from_cppc(unsigned int cpu)
> >  {
> > -     unsigned int transition_latency_ns = cppc_get_transition_latency(cpu);
> > +     int transition_latency_ns = cppc_get_transition_latency(cpu);
> >
> > -     if (transition_latency_ns == CPUFREQ_ETERNAL)
> > +     if (transition_latency_ns < 0)
> >               return CPUFREQ_DEFAULT_TRANSITION_LATENCY_NS / NSEC_PER_USEC;
> >
> >       return transition_latency_ns / NSEC_PER_USEC;
> > --- a/include/acpi/cppc_acpi.h
> > +++ b/include/acpi/cppc_acpi.h
> > @@ -160,7 +160,7 @@ extern unsigned int cppc_khz_to_perf(str
> >  extern bool acpi_cpc_valid(void);
> >  extern bool cppc_allow_fast_switch(void);
> >  extern int acpi_get_psd_map(unsigned int cpu, struct cppc_cpudata *cpu_data);
> > -extern unsigned int cppc_get_transition_latency(int cpu);
> > +extern int cppc_get_transition_latency(int cpu);
> >  extern bool cpc_ffh_supported(void);
> >  extern bool cpc_supported_by_cpu(void);
> >  extern int cpc_read_ffh(int cpunum, struct cpc_reg *reg, u64 *val);
> > @@ -216,9 +216,9 @@ static inline bool cppc_allow_fast_switc
> >  {
> >       return false;
> >  }
> > -static inline unsigned int cppc_get_transition_latency(int cpu)
> > +static inline int cppc_get_transition_latency(int cpu)
> >  {
> > -     return CPUFREQ_ETERNAL;
> > +     return -ENODATA;
> >  }
> >  static inline bool cpc_ffh_supported(void)
> >  {
> >
> >
> >
> >
>

Re: [PATCH v2 3/4] ACPI: CPPC: Do not use CPUFREQ_ETERNAL as an error value

Posted by Mario Limonciello (AMD) (kernel.org) 2 months, 3 weeks ago


On 9/25/2025 12:23 PM, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> 
> Instead of using CPUFREQ_ETERNAL for signaling an error condition
> in cppc_get_transition_latency(), change the return value type of
> that function to int and make it return a proper negative error
> code on failures.
> 
> No intentional functional impact.
> 
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Reviewed-by: Mario Limonciello (AMD) <superm1@kernel.org>

> ---
> 
> v1 -> v2:
>     * Change cppc_get_transition_latency() return value data type to int
>     * Make it return -ENODATA on errors (Mario)
>     * Update its callers accordingly
>     * Adjust the subject and changelog
>     * Add a missing empty code line to cppc_get_transition_latency()
> 
> The modifications of this patch don't affect any other patches in the series:
> 
> https://lore.kernel.org/linux-pm/8605612.T7Z3S40VBb@rafael.j.wysocki/
> 
> ---
>   drivers/acpi/cppc_acpi.c       |   15 ++++++++-------
>   drivers/cpufreq/amd-pstate.c   |    8 ++++----
>   drivers/cpufreq/cppc_cpufreq.c |    4 ++--
>   include/acpi/cppc_acpi.h       |    6 +++---
>   4 files changed, 17 insertions(+), 16 deletions(-)
> 
> --- a/drivers/acpi/cppc_acpi.c
> +++ b/drivers/acpi/cppc_acpi.c
> @@ -1876,7 +1876,7 @@ EXPORT_SYMBOL_GPL(cppc_set_perf);
>    * If desired_reg is in the SystemMemory or SystemIo ACPI address space,
>    * then assume there is no latency.
>    */
> -unsigned int cppc_get_transition_latency(int cpu_num)
> +int cppc_get_transition_latency(int cpu_num)
>   {
>   	/*
>   	 * Expected transition latency is based on the PCCT timing values
> @@ -1889,31 +1889,32 @@ unsigned int cppc_get_transition_latency
>   	 *              completion of a command before issuing the next command,
>   	 *              in microseconds.
>   	 */
> -	unsigned int latency_ns = 0;
>   	struct cpc_desc *cpc_desc;
>   	struct cpc_register_resource *desired_reg;
>   	int pcc_ss_id = per_cpu(cpu_pcc_subspace_idx, cpu_num);
>   	struct cppc_pcc_data *pcc_ss_data;
> +	int latency_ns = 0;
>   
>   	cpc_desc = per_cpu(cpc_desc_ptr, cpu_num);
>   	if (!cpc_desc)
> -		return CPUFREQ_ETERNAL;
> +		return -ENODATA;
>   
>   	desired_reg = &cpc_desc->cpc_regs[DESIRED_PERF];
>   	if (CPC_IN_SYSTEM_MEMORY(desired_reg) || CPC_IN_SYSTEM_IO(desired_reg))
>   		return 0;
> +
>   	else if (!CPC_IN_PCC(desired_reg))
> -		return CPUFREQ_ETERNAL;
> +		return -ENODATA;
>   
>   	if (pcc_ss_id < 0)
> -		return CPUFREQ_ETERNAL;
> +		return -ENODATA;
>   
>   	pcc_ss_data = pcc_data[pcc_ss_id];
>   	if (pcc_ss_data->pcc_mpar)
>   		latency_ns = 60 * (1000 * 1000 * 1000 / pcc_ss_data->pcc_mpar);
>   
> -	latency_ns = max(latency_ns, pcc_ss_data->pcc_nominal * 1000);
> -	latency_ns = max(latency_ns, pcc_ss_data->pcc_mrtt * 1000);
> +	latency_ns = max_t(int, latency_ns, pcc_ss_data->pcc_nominal * 1000);
> +	latency_ns = max_t(int, latency_ns, pcc_ss_data->pcc_mrtt * 1000);
>   
>   	return latency_ns;
>   }
> --- a/drivers/cpufreq/amd-pstate.c
> +++ b/drivers/cpufreq/amd-pstate.c
> @@ -872,10 +872,10 @@ static void amd_pstate_update_limits(str
>    */
>   static u32 amd_pstate_get_transition_delay_us(unsigned int cpu)
>   {
> -	u32 transition_delay_ns;
> +	int transition_delay_ns;
>   
>   	transition_delay_ns = cppc_get_transition_latency(cpu);
> -	if (transition_delay_ns == CPUFREQ_ETERNAL) {
> +	if (transition_delay_ns < 0) {
>   		if (cpu_feature_enabled(X86_FEATURE_AMD_FAST_CPPC))
>   			return AMD_PSTATE_FAST_CPPC_TRANSITION_DELAY;
>   		else
> @@ -891,10 +891,10 @@ static u32 amd_pstate_get_transition_del
>    */
>   static u32 amd_pstate_get_transition_latency(unsigned int cpu)
>   {
> -	u32 transition_latency;
> +	int transition_latency;
>   
>   	transition_latency = cppc_get_transition_latency(cpu);
> -	if (transition_latency  == CPUFREQ_ETERNAL)
> +	if (transition_latency < 0)
>   		return AMD_PSTATE_TRANSITION_LATENCY;
>   
>   	return transition_latency;
> --- a/drivers/cpufreq/cppc_cpufreq.c
> +++ b/drivers/cpufreq/cppc_cpufreq.c
> @@ -310,9 +310,9 @@ static int cppc_verify_policy(struct cpu
>   
>   static unsigned int get_transition_latency_from_cppc(unsigned int cpu)
>   {
> -	unsigned int transition_latency_ns = cppc_get_transition_latency(cpu);
> +	int transition_latency_ns = cppc_get_transition_latency(cpu);
>   
> -	if (transition_latency_ns == CPUFREQ_ETERNAL)
> +	if (transition_latency_ns < 0)
>   		return CPUFREQ_DEFAULT_TRANSITION_LATENCY_NS / NSEC_PER_USEC;
>   
>   	return transition_latency_ns / NSEC_PER_USEC;
> --- a/include/acpi/cppc_acpi.h
> +++ b/include/acpi/cppc_acpi.h
> @@ -160,7 +160,7 @@ extern unsigned int cppc_khz_to_perf(str
>   extern bool acpi_cpc_valid(void);
>   extern bool cppc_allow_fast_switch(void);
>   extern int acpi_get_psd_map(unsigned int cpu, struct cppc_cpudata *cpu_data);
> -extern unsigned int cppc_get_transition_latency(int cpu);
> +extern int cppc_get_transition_latency(int cpu);
>   extern bool cpc_ffh_supported(void);
>   extern bool cpc_supported_by_cpu(void);
>   extern int cpc_read_ffh(int cpunum, struct cpc_reg *reg, u64 *val);
> @@ -216,9 +216,9 @@ static inline bool cppc_allow_fast_switc
>   {
>   	return false;
>   }
> -static inline unsigned int cppc_get_transition_latency(int cpu)
> +static inline int cppc_get_transition_latency(int cpu)
>   {
> -	return CPUFREQ_ETERNAL;
> +	return -ENODATA;
>   }
>   static inline bool cpc_ffh_supported(void)
>   {
> 
> 
>