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Message-ID: <bfb134a3-521b-49d7-99da-483a627e2feb@amd.com>
Date: Tue, 3 Sep 2024 08:14:26 -0500
From: Mario Limonciello <mario.limonciello@....com>
To: Mario Limonciello <superm1@...nel.org>,
"Gautham R . Shenoy" <gautham.shenoy@....com>,
Perry Yuan <perry.yuan@....com>
Cc: "open list:X86 ARCHITECTURE (32-BIT AND 64-BIT)"
<linux-kernel@...r.kernel.org>,
"open list:CPU FREQUENCY SCALING FRAMEWORK" <linux-pm@...r.kernel.org>
Subject: Re: [PATCH 1/2] cpufreq/amd-pstate: Add an early param to disable MSR
mode
On 9/1/2024 00:00, Mario Limonciello wrote:
> From: Mario Limonciello <mario.limonciello@....com>
>
> This lets a system that supports the MSR run in shared memory mode
> instead to help replicate and debug issues.
>
> Signed-off-by: Mario Limonciello <mario.limonciello@....com>
After some offline discussion, will drop this patch. Second patch will
remain and I will queue it up for -next.
> ---
> .../admin-guide/kernel-parameters.txt | 5 +++
> Documentation/admin-guide/pm/amd-pstate.rst | 5 +++
> drivers/cpufreq/amd-pstate.c | 32 +++++++++++++------
> 3 files changed, 32 insertions(+), 10 deletions(-)
>
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index 09126bb8cc9ff..041c609ed50ea 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -383,6 +383,11 @@
> disable
> Disable amd-pstate preferred core.
>
> + amd_pstate_msr=
> + [X86]
> + disable
> + Disable amd-pstate CPPC MSR (force shared memory).
> +
> amijoy.map= [HW,JOY] Amiga joystick support
> Map of devices attached to JOY0DAT and JOY1DAT
> Format: <a>,<b>
> diff --git a/Documentation/admin-guide/pm/amd-pstate.rst b/Documentation/admin-guide/pm/amd-pstate.rst
> index d0324d44f5482..b06632556102e 100644
> --- a/Documentation/admin-guide/pm/amd-pstate.rst
> +++ b/Documentation/admin-guide/pm/amd-pstate.rst
> @@ -411,6 +411,11 @@ For systems that support ``amd-pstate`` preferred core, the core rankings will
> always be advertised by the platform. But OS can choose to ignore that via the
> kernel parameter ``amd_prefcore=disable``.
>
> +``amd_pstate_msr=disable``
> +
> +For systems that support a dedicated CPPC MSR, ignore it's use and run
> +with shared memory instead.
> +
> User Space Interface in ``sysfs`` - General
> ===========================================
>
> diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
> index 93adde45bebce..89438a3654002 100644
> --- a/drivers/cpufreq/amd-pstate.c
> +++ b/drivers/cpufreq/amd-pstate.c
> @@ -88,6 +88,7 @@ static struct cpufreq_driver amd_pstate_epp_driver;
> static int cppc_state = AMD_PSTATE_UNDEFINED;
> static bool cppc_enabled;
> static bool amd_pstate_prefcore = true;
> +static bool amd_pstate_msr = true;
> static struct quirk_entry *quirks;
>
> /*
> @@ -187,7 +188,7 @@ static s16 amd_pstate_get_epp(struct amd_cpudata *cpudata, u64 cppc_req_cached)
> u64 epp;
> int ret;
>
> - if (cpu_feature_enabled(X86_FEATURE_CPPC)) {
> + if (amd_pstate_msr) {
> if (!cppc_req_cached) {
> epp = rdmsrl_on_cpu(cpudata->cpu, MSR_AMD_CPPC_REQ,
> &cppc_req_cached);
> @@ -260,7 +261,7 @@ static int amd_pstate_set_epp(struct amd_cpudata *cpudata, u32 epp)
> int ret;
> struct cppc_perf_ctrls perf_ctrls;
>
> - if (cpu_feature_enabled(X86_FEATURE_CPPC)) {
> + if (amd_pstate_msr) {
> u64 value = READ_ONCE(cpudata->cppc_req_cached);
>
> value &= ~GENMASK_ULL(31, 24);
> @@ -813,7 +814,7 @@ static int amd_pstate_get_highest_perf(int cpu, u32 *highest_perf)
> {
> int ret;
>
> - if (cpu_feature_enabled(X86_FEATURE_CPPC)) {
> + if (amd_pstate_msr) {
> u64 cap1;
>
> ret = rdmsrl_safe_on_cpu(cpu, MSR_AMD_CPPC_CAP1, &cap1);
> @@ -1058,7 +1059,7 @@ static int amd_pstate_cpu_init(struct cpufreq_policy *policy)
> /* It will be updated by governor */
> policy->cur = policy->cpuinfo.min_freq;
>
> - if (cpu_feature_enabled(X86_FEATURE_CPPC))
> + if (amd_pstate_msr)
> policy->fast_switch_possible = true;
>
> ret = freq_qos_add_request(&policy->constraints, &cpudata->req[0],
> @@ -1288,7 +1289,7 @@ static int amd_pstate_change_mode_without_dvr_change(int mode)
>
> cppc_state = mode;
>
> - if (cpu_feature_enabled(X86_FEATURE_CPPC) || cppc_state == AMD_PSTATE_ACTIVE)
> + if (amd_pstate_msr || cppc_state == AMD_PSTATE_ACTIVE)
> return 0;
>
> for_each_present_cpu(cpu) {
> @@ -1524,7 +1525,7 @@ static int amd_pstate_epp_cpu_init(struct cpufreq_policy *policy)
> else
> policy->policy = CPUFREQ_POLICY_POWERSAVE;
>
> - if (cpu_feature_enabled(X86_FEATURE_CPPC)) {
> + if (amd_pstate_msr) {
> ret = rdmsrl_on_cpu(cpudata->cpu, MSR_AMD_CPPC_REQ, &value);
> if (ret)
> return ret;
> @@ -1612,7 +1613,7 @@ static void amd_pstate_epp_update_limit(struct cpufreq_policy *policy)
> epp = 0;
>
> /* Set initial EPP value */
> - if (cpu_feature_enabled(X86_FEATURE_CPPC)) {
> + if (amd_pstate_msr) {
> value &= ~GENMASK_ULL(31, 24);
> value |= (u64)epp << 24;
> }
> @@ -1657,7 +1658,7 @@ static void amd_pstate_epp_reenable(struct amd_cpudata *cpudata)
> value = READ_ONCE(cpudata->cppc_req_cached);
> max_perf = READ_ONCE(cpudata->highest_perf);
>
> - if (cpu_feature_enabled(X86_FEATURE_CPPC)) {
> + if (amd_pstate_msr) {
> wrmsrl_on_cpu(cpudata->cpu, MSR_AMD_CPPC_REQ, value);
> } else {
> perf_ctrls.max_perf = max_perf;
> @@ -1691,7 +1692,7 @@ static void amd_pstate_epp_offline(struct cpufreq_policy *policy)
> value = READ_ONCE(cpudata->cppc_req_cached);
>
> mutex_lock(&amd_pstate_limits_lock);
> - if (cpu_feature_enabled(X86_FEATURE_CPPC)) {
> + if (amd_pstate_msr) {
> cpudata->epp_policy = CPUFREQ_POLICY_UNKNOWN;
>
> /* Set max perf same as min perf */
> @@ -1936,7 +1937,9 @@ static int __init amd_pstate_init(void)
> }
>
> /* capability check */
> - if (cpu_feature_enabled(X86_FEATURE_CPPC)) {
> + if (amd_pstate_msr)
> + amd_pstate_msr = cpu_feature_enabled(X86_FEATURE_CPPC);
> + if (amd_pstate_msr) {
> pr_debug("AMD CPPC MSR based functionality is supported\n");
> if (cppc_state != AMD_PSTATE_ACTIVE)
> current_pstate_driver->adjust_perf = amd_pstate_adjust_perf;
> @@ -2002,8 +2005,17 @@ static int __init amd_prefcore_param(char *str)
> return 0;
> }
>
> +static int __init amd_msr_param(char *str)
> +{
> + if (!strcmp(str, "disable"))
> + amd_pstate_msr = false;
> +
> + return 0;
> +}
> +
> early_param("amd_pstate", amd_pstate_param);
> early_param("amd_prefcore", amd_prefcore_param);
> +early_param("amd_pstate_msr", amd_msr_param);
>
> MODULE_AUTHOR("Huang Rui <ray.huang@....com>");
> MODULE_DESCRIPTION("AMD Processor P-state Frequency Driver");
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