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

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Message-ID: <53962105-07cb-d964-28d0-1cc4d2e7fe8b@amd.com>
Date:   Wed, 8 Sep 2021 14:14:37 -0500
From:   "Fontenot, Nathan" <Nathan.Fontenot@....com>
To:     Huang Rui <ray.huang@....com>,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Shuah Khan <skhan@...uxfoundation.org>,
        Borislav Petkov <bp@...e.de>, Ingo Molnar <mingo@...nel.org>,
        linux-pm@...r.kernel.org
Cc:     Deepak Sharma <deepak.sharma@....com>,
        Alex Deucher <alexander.deucher@....com>,
        Mario Limonciello <mario.limonciello@....com>,
        Jinzhou Su <Jinzhou.Su@....com>,
        Xiaojian Du <Xiaojian.Du@....com>,
        linux-kernel@...r.kernel.org, x86@...nel.org
Subject: Re: [PATCH 03/19] ACPI: CPPC: add cppc enable register function

On 9/8/2021 9:59 AM, Huang Rui wrote:
> From: Jinzhou Su <Jinzhou.Su@....com>
> 
> Export the cppc enable register function for future use.
> 
> Signed-off-by: Jinzhou Su <Jinzhou.Su@....com>
> Signed-off-by: Huang Rui <ray.huang@....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.
> + * @cpu: CPU for which to enable CPPC register.
> + * @enable: enable field to write into share memory.
> + *
> + * 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;
> +	}
> +
> +	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);

Shouldn't we be checking the return value from send_pcc_cmd()?

Also, if the call to send_pcc_cmd() fails do we need to update
enable_reg? i.e. cpc_write(..., !enable);

-Nathan

> +		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;
> -- 
> 2.25.1
>