linux-kernel - Re: [PATCH v3 3/4] ACPI: CPPC: Add autonomous selection ABIs

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Message-ID: <e581fa05-9b4e-46e6-9172-83704bfa8ab2@arm.com>
Date: Tue, 17 Dec 2024 14:48:29 +0100
From: Pierre Gondois <pierre.gondois@....com>
To: Lifeng Zheng <zhenglifeng1@...wei.com>, Huang Rui <ray.huang@....com>,
 "Gautham R. Shenoy" <gautham.shenoy@....com>,
 Mario Limonciello <mario.limonciello@....com>
Cc: acpica-devel@...ts.linux.dev, lenb@...nel.org, viresh.kumar@...aro.org,
 robert.moore@...el.com, rafael@...nel.org, linux-acpi@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org, linuxarm@...wei.com,
 ionela.voinescu@....com, jonathan.cameron@...wei.com,
 zhanjie9@...ilicon.com, lihuisong@...wei.com, hepeng68@...wei.com,
 fanghao11@...wei.com
Subject: Re: [PATCH v3 3/4] ACPI: CPPC: Add autonomous selection ABIs

Hello Lifeng, Huang, Gautham, Mario,

On 12/16/24 10:16, Lifeng Zheng wrote:
> cppc_set_epp - write energy performance preference register
> 
> cppc_get_auto_act_window - read autonomous activity window register
> 
> cppc_set_auto_act_window - write autonomous activity window register
> 
> cppc_get_auto_sel - read autonomous selection enable register
> 
> Signed-off-by: Lifeng Zheng <zhenglifeng1@...wei.com>
> ---
>   drivers/acpi/cppc_acpi.c | 44 ++++++++++++++++++++++++++++++++++++++++
>   include/acpi/cppc_acpi.h | 20 ++++++++++++++++++
>   2 files changed, 64 insertions(+)
> 
> diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c
> index 83c7fcad74ad..645f2366c888 100644
> --- a/drivers/acpi/cppc_acpi.c
> +++ b/drivers/acpi/cppc_acpi.c
> @@ -1595,6 +1595,50 @@ int cppc_set_epp_perf(int cpu, struct cppc_perf_ctrls *perf_ctrls, bool enable)
>   }
>   EXPORT_SYMBOL_GPL(cppc_set_epp_perf);
>   
> +/**
> + * cppc_set_epp() - Write the EPP register.
> + * @cpu: CPU on which to write register.
> + * @epp_val: Value to write to the EPP register.
> + */
> +int cppc_set_epp(int cpu, u64 epp_val)
> +{
> +	return cppc_set_reg_val(cpu, ENERGY_PERF, epp_val);
> +}
> +EXPORT_SYMBOL_GPL(cppc_set_epp);
> +
> +/**
> + * cppc_get_auto_act_window() - Read autonomous activity window register.
> + * @cpu: CPU from which to read register.
> + * @auto_act_window: Return address.
> + */
> +int cppc_get_auto_act_window(int cpu, u64 *auto_act_window)

As there is only one way to interpret the value of the
'Autonomous Activity Window Register', maybe the logic to convert
from/to the register value to a value in us should be placed here
rather than in the cppc_cpufreq driver.
Meaning, maybe the prototype should be:

int cppc_get_auto_act_window(int cpu, unsigned int *auto_act_window);

Similar remark for cppc_set_epp() and other functions.

> +{
> +	return cppc_get_reg_val(cpu, AUTO_ACT_WINDOW, auto_act_window);
> +}
> +EXPORT_SYMBOL_GPL(cppc_get_auto_act_window);
> +
> +/**
> + * cppc_set_auto_act_window() - Write autonomous activity window register.
> + * @cpu: CPU on which to write register.
> + * @auto_act_window: Value to write to the autonomous activity window register.
> + */
> +int cppc_set_auto_act_window(int cpu, u64 auto_act_window)
> +{
> +	return cppc_set_reg_val(cpu, AUTO_ACT_WINDOW, auto_act_window);
> +}
> +EXPORT_SYMBOL_GPL(cppc_set_auto_act_window);
> +
> +/**
> + * cppc_get_auto_sel() - Read autonomous selection register.
> + * @cpu: CPU from which to read register.
> + * @auto_sel: Return address.
> + */
> +int cppc_get_auto_sel(int cpu, u64 *auto_sel)

Similarly, maybe it would be better to use:
int cppc_get_auto_sel(int cpu, bool *auto_sel);

> +{
> +	return cppc_get_reg_val(cpu, AUTO_SEL_ENABLE, auto_sel);
> +}
> +EXPORT_SYMBOL_GPL(cppc_get_auto_sel);
> +
>   /**
>    * cppc_get_auto_sel_caps - Read autonomous selection register.
>    * @cpunum : CPU from which to read register.
> diff --git a/include/acpi/cppc_acpi.h b/include/acpi/cppc_acpi.h
> index 62d368bcd9ec..134931b081a0 100644
> --- a/include/acpi/cppc_acpi.h
> +++ b/include/acpi/cppc_acpi.h
> @@ -159,6 +159,10 @@ extern int cpc_read_ffh(int cpunum, struct cpc_reg *reg, u64 *val);
>   extern int cpc_write_ffh(int cpunum, struct cpc_reg *reg, u64 val);
>   extern int cppc_get_epp_perf(int cpunum, u64 *epp_perf);
>   extern int cppc_set_epp_perf(int cpu, struct cppc_perf_ctrls *perf_ctrls, bool enable);
> +extern int cppc_set_epp(int cpu, u64 epp_val);
> +extern int cppc_get_auto_act_window(int cpu, u64 *auto_act_window);
> +extern int cppc_set_auto_act_window(int cpu, u64 auto_act_window);
> +extern int cppc_get_auto_sel(int cpu, u64 *auto_sel);
>   extern int cppc_get_auto_sel_caps(int cpunum, struct cppc_perf_caps *perf_caps);

This is a bit annoying, but maybe only one function between:
- cppc_get_auto_sel_caps()
- cppc_get_auto_sel()
is necessary.

I added the owners of the amd-pstate driver to ask if this would
be ok to replace cppc_get_auto_sel_caps() by cppc_get_auto_sel().

>   extern int cppc_set_auto_sel(int cpu, bool enable);
>   extern int amd_get_highest_perf(unsigned int cpu, u32 *highest_perf);
> @@ -225,6 +229,22 @@ static inline int cppc_set_epp_perf(int cpu, struct cppc_perf_ctrls *perf_ctrls,
>   {
>   	return -EOPNOTSUPP;
>   }
> +static inline int cppc_set_epp(int cpu, u64 epp_val)
> +{
> +	return -EOPNOTSUPP;
> +}
> +static inline int cppc_get_auto_act_window(int cpu, u64 *auto_act_window)
> +{
> +	return -EOPNOTSUPP;
> +}
> +static inline int cppc_set_auto_act_window(int cpu, u64 auto_act_window)
> +{
> +	return -EOPNOTSUPP;
> +}
> +static inline int cppc_get_auto_sel(int cpu, u64 *auto_sel)
> +{
> +	return -EOPNOTSUPP;
> +}
>   static inline int cppc_get_epp_perf(int cpunum, u64 *epp_perf)
>   {
>   	return -EOPNOTSUPP;