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Date: Mon, 7 Nov 2022 12:44:35 -0600
From: "Limonciello, Mario" <mario.limonciello@....com>
To: Perry Yuan <Perry.Yuan@....com>, rafael.j.wysocki@...el.com,
ray.huang@....com, viresh.kumar@...aro.org
Cc: Deepak.Sharma@....com, Nathan.Fontenot@....com,
Alexander.Deucher@....com, Shimmer.Huang@....com,
Xiaojian.Du@....com, Li.Meng@....com, linux-pm@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 1/8] ACPI: CPPC: Add AMD pstate energy performance
preference cppc control
On 11/7/2022 11:56, Perry Yuan wrote:
> Add the EPP(Energy Performance Preference) support for the
> AMD SoCs without the dedicated CPPC MSR, those SoCs need to add this
> cppc acpi functions to update EPP values and desired perf value.
As far as I can tell this is generic code. Although the reason you're
submitting it is for enabling AMD SoCs, the commit message should be
worded as such.
>
> In order to get EPP worked, cppc_get_epp_caps() will query EPP preference
> value and cppc_set_epp_perf() will set EPP new value.
> Before the EPP works, pstate driver will use cppc_set_auto_epp() to
> enable EPP function from firmware firstly.
This could more succinctly say:
"Add support for setting and querying EPP preferences to the generic
CPPC driver. This enables downstream drivers such as amd-pstate to discover
and use these values."
>
> Signed-off-by: Perry Yuan <Perry.Yuan@....com>
> ---
> drivers/acpi/cppc_acpi.c | 126 +++++++++++++++++++++++++++++++++++++++
> include/acpi/cppc_acpi.h | 17 ++++++
> 2 files changed, 143 insertions(+)
>
> diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c
> index 093675b1a1ff..d9c38dee1f48 100644
> --- a/drivers/acpi/cppc_acpi.c
> +++ b/drivers/acpi/cppc_acpi.c
> @@ -1365,6 +1365,132 @@ int cppc_get_perf_ctrs(int cpunum, struct cppc_perf_fb_ctrs *perf_fb_ctrs)
> }
> EXPORT_SYMBOL_GPL(cppc_get_perf_ctrs);
>
> +/**
> + * cppc_get_epp_caps - Get the energy preference register value.
> + * @cpunum: CPU from which to get epp preference level.
> + * @perf_caps: Return address.
> + *
> + * Return: 0 for success, -EIO otherwise.
> + */
> +int cppc_get_epp_caps(int cpunum, struct cppc_perf_caps *perf_caps)
> +{
> + struct cpc_desc *cpc_desc = per_cpu(cpc_desc_ptr, cpunum);
> + struct cpc_register_resource *energy_perf_reg;
> + u64 energy_perf;
> +
> + if (!cpc_desc) {
> + pr_warn("No CPC descriptor for CPU:%d\n", cpunum);
> + return -ENODEV;
> + }
> +
> + energy_perf_reg = &cpc_desc->cpc_regs[ENERGY_PERF];
> +
> + if (!CPC_SUPPORTED(energy_perf_reg))
> + pr_warn("energy perf reg update is unsupported!\n");
No need to add a explanation point at the end.
As this is a per-CPU message I wonder if this would be better as
pr_warn_once()? Othewrise some systems with large numbers of cores
might potentially show this message quite a few times.
> +
> + if (CPC_IN_PCC(energy_perf_reg)) {
> + int pcc_ss_id = per_cpu(cpu_pcc_subspace_idx, cpunum);
> + struct cppc_pcc_data *pcc_ss_data = NULL;
> + int ret = 0;
> +
> + if (pcc_ss_id < 0)
> + return -ENODEV;
> +
> + pcc_ss_data = pcc_data[pcc_ss_id];
> +
> + down_write(&pcc_ss_data->pcc_lock);
> +
> + if (send_pcc_cmd(pcc_ss_id, CMD_READ) >= 0) {
> + cpc_read(cpunum, energy_perf_reg, &energy_perf);
> + perf_caps->energy_perf = energy_perf;
> + } else {
> + ret = -EIO;
> + }
> +
> + up_write(&pcc_ss_data->pcc_lock);
> +
> + return ret;
> + }
> +
> + return 0;
> +}
> +EXPORT_SYMBOL_GPL(cppc_get_epp_caps);
> +
> +int cppc_set_auto_epp(int cpu, bool enable)
> +{
> + int pcc_ss_id = per_cpu(cpu_pcc_subspace_idx, cpu);
> + struct cpc_register_resource *auto_sel_reg;
> + struct cpc_desc *cpc_desc = per_cpu(cpc_desc_ptr, cpu);
> + struct cppc_pcc_data *pcc_ss_data = NULL;
> + int ret = -EINVAL;
> +
> + if (!cpc_desc) {
> + pr_warn("No CPC descriptor for CPU:%d\n", cpu);
Is this actually warn worthy? I would think it's fine a debug like we
have for the other _CPC missing messages.
> + return -EINVAL;
> + }
> +
> + auto_sel_reg = &cpc_desc->cpc_regs[AUTO_SEL_ENABLE];
> +
> + if (CPC_IN_PCC(auto_sel_reg)) {
> + if (pcc_ss_id < 0)
> + return -ENODEV;
> +
> + ret = cpc_write(cpu, auto_sel_reg, enable);
> + if (ret)
> + return ret;
> +
> + pcc_ss_data = pcc_data[pcc_ss_id];
> +
> + down_write(&pcc_ss_data->pcc_lock);
> + /* after writing CPC, transfer the ownership of PCC to platform */
> + ret = send_pcc_cmd(pcc_ss_id, CMD_WRITE);
> + up_write(&pcc_ss_data->pcc_lock);
> + return ret;
> + }
> +
> + return cpc_write(cpu, auto_sel_reg, enable);
> +}
> +EXPORT_SYMBOL_GPL(cppc_set_auto_epp);
> +
> +/*
> + * Set Energy Performance Preference Register value through
> + * Performance Controls Interface
> + */
> +int cppc_set_epp_perf(int cpu, struct cppc_perf_ctrls *perf_ctrls)
> +{
> + int pcc_ss_id = per_cpu(cpu_pcc_subspace_idx, cpu);
> + struct cpc_register_resource *epp_set_reg;
> + struct cpc_desc *cpc_desc = per_cpu(cpc_desc_ptr, cpu);
> + struct cppc_pcc_data *pcc_ss_data = NULL;
> + int ret = -EINVAL;
> +
> + if (!cpc_desc) {
> + pr_warn("No CPC descriptor for CPU:%d\n", cpu);
Is this actually warn worthy? I would think it's fine a debug like we
have for the other _CPC missing messages.
> + return -EINVAL;
> + }
> +
> + epp_set_reg = &cpc_desc->cpc_regs[ENERGY_PERF];
> +
> + if (CPC_IN_PCC(epp_set_reg)) {
> + if (pcc_ss_id < 0)
> + return -ENODEV;
> +
> + ret = cpc_write(cpu, epp_set_reg, perf_ctrls->energy_perf);
> + if (ret)
> + return ret;
> +
> + pcc_ss_data = pcc_data[pcc_ss_id];
> +
> + down_write(&pcc_ss_data->pcc_lock);
> + /* after writing CPC, transfer the ownership of PCC to platform */
> + ret = send_pcc_cmd(pcc_ss_id, CMD_WRITE);
> + up_write(&pcc_ss_data->pcc_lock);
cppc_set_auto_epp and cppc_set_epp_perf have nearly the same code in the
if block. I wonder if it's worth having a static helper function for
this purpose that takes "reg" and "value" as arguments?
> + }
> +
> + return ret;
> +}
> +EXPORT_SYMBOL_GPL(cppc_set_epp_perf);
> +
> /**
> * cppc_set_enable - Set to enable CPPC on the processor by writing the
> * Continuous Performance Control package EnableRegister field.
> diff --git a/include/acpi/cppc_acpi.h b/include/acpi/cppc_acpi.h
> index c5614444031f..10d91aeedaca 100644
> --- a/include/acpi/cppc_acpi.h
> +++ b/include/acpi/cppc_acpi.h
> @@ -108,12 +108,14 @@ struct cppc_perf_caps {
> u32 lowest_nonlinear_perf;
> u32 lowest_freq;
> u32 nominal_freq;
> + u32 energy_perf;
> };
>
> struct cppc_perf_ctrls {
> u32 max_perf;
> u32 min_perf;
> u32 desired_perf;
> + u32 energy_perf;
> };
>
> struct cppc_perf_fb_ctrs {
> @@ -149,6 +151,9 @@ 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);
> extern int cpc_write_ffh(int cpunum, struct cpc_reg *reg, u64 val);
> +extern int cppc_set_auto_epp(int cpu, bool enable);
> +extern int cppc_get_epp_caps(int cpunum, struct cppc_perf_caps *perf_caps);
> +extern int cppc_set_epp_perf(int cpu, struct cppc_perf_ctrls *perf_ctrls);
> #else /* !CONFIG_ACPI_CPPC_LIB */
> static inline int cppc_get_desired_perf(int cpunum, u64 *desired_perf)
> {
> @@ -202,6 +207,18 @@ static inline int cpc_write_ffh(int cpunum, struct cpc_reg *reg, u64 val)
> {
> return -ENOTSUPP;
> }
> +static inline int cppc_set_auto_epp(int cpu, bool enable)
> +{
> + return -ENOTSUPP;
> +}
> +static inline int cppc_set_epp_perf(int cpu, struct cppc_perf_ctrls *perf_ctrls)
> +{
> + return -ENOTSUPP;
> +}
> +static inline int cppc_get_epp_caps(int cpunum, struct cppc_perf_caps *perf_caps)
> +{
> + return -ENOTSUPP;
> +}
> #endif /* !CONFIG_ACPI_CPPC_LIB */
>
> #endif /* _CPPC_ACPI_H*/
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