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Date: Thu, 10 Nov 2022 15:49:33 +0100
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: "Limonciello, Mario" <mario.limonciello@....com>,
Perry Yuan <perry.yuan@....com>
Cc: rafael.j.wysocki@...el.com, ray.huang@....com,
viresh.kumar@...aro.org, 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 Mon, Nov 7, 2022 at 7:44 PM Limonciello, Mario
<mario.limonciello@....com> wrote:
>
> 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.
pr_info_once() would suffice IMO.
> > +
> > + 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;
> > + }
What if CPC is not in PCC?
Would returning 0 then work for all users?
> > +
> > + 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?
>
> > + }
And what about the non-PCC case here?
> > +
> > + 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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