Re: [PATCH 03/19] ACPI: CPPC: add cppc enable register function

[Shuah Khan <skhan@linuxfoundation.org>]

On 9/8/21 8:59 AM, Huang Rui wrote:
> From: Jinzhou Su <Jinzhou.Su@amd.com>
> 
> Export the cppc enable register function for future use.

This patch also adds a new function. How about saying something about
adding a new function.

> 
> Signed-off-by: Jinzhou Su <Jinzhou.Su@amd.com>
> Signed-off-by: Huang Rui <ray.huang@amd.com>
> ---
>   drivers/acpi/cppc_acpi.c | 42 ++++++++++++++++++++++++++++++++++++++++
>   include/acpi/cppc_acpi.h |  5 +++++
>   2 files changed, 47 insertions(+)
> 
> diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c
> index a4d4eebba1da..de4b30545215 100644
> --- a/drivers/acpi/cppc_acpi.c
> +++ b/drivers/acpi/cppc_acpi.c
> @@ -1220,6 +1220,48 @@ int cppc_get_perf_ctrs(int cpunum, struct cppc_perf_fb_ctrs *perf_fb_ctrs)
>   }
>   EXPORT_SYMBOL_GPL(cppc_get_perf_ctrs);
>   
> +/**
> + * cppc_set_enable - Set to enable CPPC register.

Please make this more descriptive - does it write to register
What is the behavior in error paths etc.

> + * @cpu: CPU for which to enable CPPC register.
> + * @enable: enable field to write into share memory.

What should this be? What are the valid values to write?
Also aren't we adding this to header file where prtotype
is defined these days?

> + *
> + * Return: 0 for success, -ERRNO otherwise.
> + */
> +int cppc_set_enable(int cpu, u32 enable)
> +{
> +	int pcc_ss_id = per_cpu(cpu_pcc_subspace_idx, cpu);
> +	struct cpc_register_resource *enable_reg;
> +	struct cpc_desc *cpc_desc = per_cpu(cpc_desc_ptr, cpu);
> +	struct cppc_pcc_data *pcc_ss_data = NULL;
> +	int ret = -1;
> +
> +	if (!cpc_desc) {
> +		pr_debug("No CPC descriptor for CPU:%d\n", cpu);
> +		return -ENODEV;
> +	}
> +

Don't we need to do some error checking on input args? What is the
valid range for cpu and enbale?

> +	enable_reg = &cpc_desc->cpc_regs[ENABLE];
> +
> +	if (CPC_IN_PCC(enable_reg)) {
> +
> +		if (pcc_ss_id < 0)
> +			return -EIO;
> +
> +		ret = cpc_write(cpu, enable_reg, enable);
> +		if (ret)
> +			return ret;
> +
> +		pcc_ss_data = pcc_data[pcc_ss_id];
> +
> +		down_write(&pcc_ss_data->pcc_lock);
> +		send_pcc_cmd(pcc_ss_id, CMD_WRITE);

Could this fail?

> +		up_write(&pcc_ss_data->pcc_lock);
> +	}
> +
> +	return ret;
> +}
> +EXPORT_SYMBOL_GPL(cppc_set_enable);
> +
>   /**
>    * cppc_set_perf - Set a CPU's performance controls.
>    * @cpu: CPU for which to set performance controls.
> diff --git a/include/acpi/cppc_acpi.h b/include/acpi/cppc_acpi.h
> index 9f4985b4d64d..3fdae40a75fc 100644
> --- a/include/acpi/cppc_acpi.h
> +++ b/include/acpi/cppc_acpi.h
> @@ -137,6 +137,7 @@ struct cppc_cpudata {
>   extern int cppc_get_desired_perf(int cpunum, u64 *desired_perf);
>   extern int cppc_get_perf_ctrs(int cpu, struct cppc_perf_fb_ctrs *perf_fb_ctrs);
>   extern int cppc_set_perf(int cpu, struct cppc_perf_ctrls *perf_ctrls);
> +extern int cppc_set_enable(int cpu, u32 enable);
>   extern int cppc_get_perf_caps(int cpu, struct cppc_perf_caps *caps);
>   extern bool acpi_cpc_valid(void);
>   extern int acpi_get_psd_map(unsigned int cpu, struct cppc_cpudata *cpu_data);
> @@ -157,6 +158,10 @@ static inline int cppc_set_perf(int cpu, struct cppc_perf_ctrls *perf_ctrls)
>   {
>   	return -ENOTSUPP;
>   }
> +static inline int cppc_set_enable(int cpu, u32 enable)
> +{
> +	return -ENOTSUPP;
> +}
>   static inline int cppc_get_perf_caps(int cpu, struct cppc_perf_caps *caps)
>   {
>   	return -ENOTSUPP;
> 

thanks,
-- Shuah