drivers/acpi/cppc_acpi.c | 6 +++--- drivers/cpufreq/amd-pstate.c | 4 ++-- drivers/cpufreq/cppc_cpufreq.c | 2 +- include/acpi/cppc_acpi.h | 4 +++- include/linux/cpufreq.h | 3 --- 5 files changed, 9 insertions(+), 10 deletions(-)
From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Instead of using CPUFREQ_ETERNAL for signaling error conditions in
cppc_get_transition_latency(), introduce CPPC_NO_DATA specifically
for this purpose and update all of the callers of this function to
use it.
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---
drivers/acpi/cppc_acpi.c | 6 +++---
drivers/cpufreq/amd-pstate.c | 4 ++--
drivers/cpufreq/cppc_cpufreq.c | 2 +-
include/acpi/cppc_acpi.h | 4 +++-
include/linux/cpufreq.h | 3 ---
5 files changed, 9 insertions(+), 10 deletions(-)
--- a/drivers/acpi/cppc_acpi.c
+++ b/drivers/acpi/cppc_acpi.c
@@ -1897,16 +1897,16 @@ unsigned int cppc_get_transition_latency
cpc_desc = per_cpu(cpc_desc_ptr, cpu_num);
if (!cpc_desc)
- return CPUFREQ_ETERNAL;
+ return CPPC_NO_DATA;
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 CPPC_NO_DATA;
if (pcc_ss_id < 0)
- return CPUFREQ_ETERNAL;
+ return CPPC_NO_DATA;
pcc_ss_data = pcc_data[pcc_ss_id];
if (pcc_ss_data->pcc_mpar)
--- a/drivers/cpufreq/amd-pstate.c
+++ b/drivers/cpufreq/amd-pstate.c
@@ -875,7 +875,7 @@ static u32 amd_pstate_get_transition_del
u32 transition_delay_ns;
transition_delay_ns = cppc_get_transition_latency(cpu);
- if (transition_delay_ns == CPUFREQ_ETERNAL) {
+ if (transition_delay_ns == CPPC_NO_DATA) {
if (cpu_feature_enabled(X86_FEATURE_AMD_FAST_CPPC))
return AMD_PSTATE_FAST_CPPC_TRANSITION_DELAY;
else
@@ -894,7 +894,7 @@ static u32 amd_pstate_get_transition_lat
u32 transition_latency;
transition_latency = cppc_get_transition_latency(cpu);
- if (transition_latency == CPUFREQ_ETERNAL)
+ if (transition_latency == CPPC_NO_DATA)
return AMD_PSTATE_TRANSITION_LATENCY;
return transition_latency;
--- a/drivers/cpufreq/cppc_cpufreq.c
+++ b/drivers/cpufreq/cppc_cpufreq.c
@@ -312,7 +312,7 @@ static unsigned int get_transition_laten
{
unsigned int transition_latency_ns = cppc_get_transition_latency(cpu);
- if (transition_latency_ns == CPUFREQ_ETERNAL)
+ if (transition_latency_ns == CPPC_NO_DATA)
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
@@ -41,6 +41,8 @@
#define CPPC_ENERGY_PERF_MAX (0xFF)
+#define CPPC_NO_DATA (unsigned int)(-1)
+
/* Each register has the folowing format. */
struct cpc_reg {
u8 descriptor;
@@ -218,7 +220,7 @@ static inline bool cppc_allow_fast_switc
}
static inline unsigned int cppc_get_transition_latency(int cpu)
{
- return CPUFREQ_ETERNAL;
+ return CPPC_NO_DATA;
}
static inline bool cpc_ffh_supported(void)
{
On 9/25/2025 10:46 AM, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
>
> Instead of using CPUFREQ_ETERNAL for signaling error conditions in
> cppc_get_transition_latency(), introduce CPPC_NO_DATA specifically
> for this purpose and update all of the callers of this function to
> use it.
>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> ---
> drivers/acpi/cppc_acpi.c | 6 +++---
> drivers/cpufreq/amd-pstate.c | 4 ++--
> drivers/cpufreq/cppc_cpufreq.c | 2 +-
> include/acpi/cppc_acpi.h | 4 +++-
> include/linux/cpufreq.h | 3 ---
> 5 files changed, 9 insertions(+), 10 deletions(-)
>
> --- a/drivers/acpi/cppc_acpi.c
> +++ b/drivers/acpi/cppc_acpi.c
> @@ -1897,16 +1897,16 @@ unsigned int cppc_get_transition_latency
>
> cpc_desc = per_cpu(cpc_desc_ptr, cpu_num);
> if (!cpc_desc)
> - return CPUFREQ_ETERNAL;
> + return CPPC_NO_DATA;
>
> 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 CPPC_NO_DATA;
>
> if (pcc_ss_id < 0)
> - return CPUFREQ_ETERNAL;
> + return CPPC_NO_DATA;
>
> pcc_ss_data = pcc_data[pcc_ss_id];
> if (pcc_ss_data->pcc_mpar)
> --- a/drivers/cpufreq/amd-pstate.c
> +++ b/drivers/cpufreq/amd-pstate.c
> @@ -875,7 +875,7 @@ static u32 amd_pstate_get_transition_del
> u32 transition_delay_ns;
>
> transition_delay_ns = cppc_get_transition_latency(cpu);
> - if (transition_delay_ns == CPUFREQ_ETERNAL) {
> + if (transition_delay_ns == CPPC_NO_DATA) {
> if (cpu_feature_enabled(X86_FEATURE_AMD_FAST_CPPC))
> return AMD_PSTATE_FAST_CPPC_TRANSITION_DELAY;
> else
> @@ -894,7 +894,7 @@ static u32 amd_pstate_get_transition_lat
> u32 transition_latency;
>
> transition_latency = cppc_get_transition_latency(cpu);
> - if (transition_latency == CPUFREQ_ETERNAL)
> + if (transition_latency == CPPC_NO_DATA)
> return AMD_PSTATE_TRANSITION_LATENCY;
>
> return transition_latency;
> --- a/drivers/cpufreq/cppc_cpufreq.c
> +++ b/drivers/cpufreq/cppc_cpufreq.c
> @@ -312,7 +312,7 @@ static unsigned int get_transition_laten
> {
> unsigned int transition_latency_ns = cppc_get_transition_latency(cpu);
>
> - if (transition_latency_ns == CPUFREQ_ETERNAL)
> + if (transition_latency_ns == CPPC_NO_DATA)
> 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
> @@ -41,6 +41,8 @@
>
> #define CPPC_ENERGY_PERF_MAX (0xFF)
>
> +#define CPPC_NO_DATA (unsigned int)(-1)
> +
Would it be cleaner to just change all the functions that can return
CPPC_NO_DATA to int instead of unsigned int and instead use -ENODATA?
> /* Each register has the folowing format. */
> struct cpc_reg {
> u8 descriptor;
> @@ -218,7 +220,7 @@ static inline bool cppc_allow_fast_switc
> }
> static inline unsigned int cppc_get_transition_latency(int cpu)
> {
> - return CPUFREQ_ETERNAL;
> + return CPPC_NO_DATA;
> }
> static inline bool cpc_ffh_supported(void)
> {
>
>
>
On Thu, Sep 25, 2025 at 6:35 PM Mario Limonciello
<mario.limonciello@amd.com> wrote:
>
>
>
> On 9/25/2025 10:46 AM, Rafael J. Wysocki wrote:
> > From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> >
> > Instead of using CPUFREQ_ETERNAL for signaling error conditions in
> > cppc_get_transition_latency(), introduce CPPC_NO_DATA specifically
> > for this purpose and update all of the callers of this function to
> > use it.
> >
> > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> > ---
> > drivers/acpi/cppc_acpi.c | 6 +++---
> > drivers/cpufreq/amd-pstate.c | 4 ++--
> > drivers/cpufreq/cppc_cpufreq.c | 2 +-
> > include/acpi/cppc_acpi.h | 4 +++-
> > include/linux/cpufreq.h | 3 ---
> > 5 files changed, 9 insertions(+), 10 deletions(-)
> >
> > --- a/drivers/acpi/cppc_acpi.c
> > +++ b/drivers/acpi/cppc_acpi.c
> > @@ -1897,16 +1897,16 @@ unsigned int cppc_get_transition_latency
> >
> > cpc_desc = per_cpu(cpc_desc_ptr, cpu_num);
> > if (!cpc_desc)
> > - return CPUFREQ_ETERNAL;
> > + return CPPC_NO_DATA;
> >
> > 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 CPPC_NO_DATA;
> >
> > if (pcc_ss_id < 0)
> > - return CPUFREQ_ETERNAL;
> > + return CPPC_NO_DATA;
> >
> > pcc_ss_data = pcc_data[pcc_ss_id];
> > if (pcc_ss_data->pcc_mpar)
> > --- a/drivers/cpufreq/amd-pstate.c
> > +++ b/drivers/cpufreq/amd-pstate.c
> > @@ -875,7 +875,7 @@ static u32 amd_pstate_get_transition_del
> > u32 transition_delay_ns;
> >
> > transition_delay_ns = cppc_get_transition_latency(cpu);
> > - if (transition_delay_ns == CPUFREQ_ETERNAL) {
> > + if (transition_delay_ns == CPPC_NO_DATA) {
> > if (cpu_feature_enabled(X86_FEATURE_AMD_FAST_CPPC))
> > return AMD_PSTATE_FAST_CPPC_TRANSITION_DELAY;
> > else
> > @@ -894,7 +894,7 @@ static u32 amd_pstate_get_transition_lat
> > u32 transition_latency;
> >
> > transition_latency = cppc_get_transition_latency(cpu);
> > - if (transition_latency == CPUFREQ_ETERNAL)
> > + if (transition_latency == CPPC_NO_DATA)
> > return AMD_PSTATE_TRANSITION_LATENCY;
> >
> > return transition_latency;
> > --- a/drivers/cpufreq/cppc_cpufreq.c
> > +++ b/drivers/cpufreq/cppc_cpufreq.c
> > @@ -312,7 +312,7 @@ static unsigned int get_transition_laten
> > {
> > unsigned int transition_latency_ns = cppc_get_transition_latency(cpu);
> >
> > - if (transition_latency_ns == CPUFREQ_ETERNAL)
> > + if (transition_latency_ns == CPPC_NO_DATA)
> > 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
> > @@ -41,6 +41,8 @@
> >
> > #define CPPC_ENERGY_PERF_MAX (0xFF)
> >
> > +#define CPPC_NO_DATA (unsigned int)(-1)
> > +
>
> Would it be cleaner to just change all the functions that can return
> CPPC_NO_DATA to int instead of unsigned int and instead use -ENODATA?
Yes, that'll work too.
I'll send an update of this patch shortly.
> > /* Each register has the folowing format. */
> > struct cpc_reg {
> > u8 descriptor;
> > @@ -218,7 +220,7 @@ static inline bool cppc_allow_fast_switc
> > }
> > static inline unsigned int cppc_get_transition_latency(int cpu)
> > {
> > - return CPUFREQ_ETERNAL;
> > + return CPPC_NO_DATA;
> > }
> > static inline bool cpc_ffh_supported(void)
> > {
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)
{
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)
> {
>
>
>
>
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)
> > {
> >
> >
> >
> >
>
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)
> {
>
>
>
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