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Message-ID: <Y9lUgxevhdlv840K@beas>
Date: Tue, 31 Jan 2023 17:48:51 +0000
From: Wyes Karny <wyes.karny@....com>
To: Mario Limonciello <mario.limonciello@....com>
Cc: Rafael J Wysocki <rafael@...nel.org>,
Huang Rui <ray.huang@....com>,
Jonathan Corbet <corbet@....net>,
Viresh Kumar <viresh.kumar@...aro.org>, Perry.Yuan@....com,
linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-pm@...r.kernel.org, Bagas Sanjaya <bagasdotme@...il.com>,
santosh.shukla@....com, Len Brown <lenb@...nel.org>,
Robert Moore <robert.moore@...el.com>,
Borislav Petkov <bp@...en8.de>,
Ananth Narayan <ananth.narayan@....com>,
gautham.shenoy@....com, Tor Vic <torvic9@...lbox.org>
Subject: Re: [PATCH v4 5/6] cpufreq: amd_pstate: Add guided mode control
support via sysfs
On 31 Jan 07:45, Mario Limonciello wrote:
> On 1/30/23 23:21, Wyes Karny wrote:
> > amd_pstate driver's `status` sysfs entry helps to control the driver's
> > mode dynamically by user. After the addition of guided mode the
> > combinations of mode transitions have been increased (16 combinations).
> > Therefore optimise the amd_pstate_update_status function by implementing
> > a state transition table.
> >
> > There are 4 states amd_pstate supports, namely: 'disable', 'passive',
> > 'active', and 'guided'. The transition from any state to any other
> > state is possible after this change. Only if the state requested matches
> > with the current state then -EBUSY value is returned.
>
> I realized this after I finished reviewing doc patch, but you probably want
> to explain -EBUSY return code in documentation patch too.
Yes, I'll add this to documentation. Thanks!
>
> >
> > Sysfs interface:
> >
> > To disable amd_pstate driver:
> > # echo disable > /sys/devices/system/cpu/amd_pstate/status
> >
> > To enable passive mode:
> > # echo passive > /sys/devices/system/cpu/amd_pstate/status
> >
> > To change mode to active:
> > # echo active > /sys/devices/system/cpu/amd_pstate/status
> >
> > To change mode to guided:
> > # echo guided > /sys/devices/system/cpu/amd_pstate/status
> >
> > Signed-off-by: Wyes Karny <wyes.karny@....com>
> > ---
> > drivers/cpufreq/amd-pstate.c | 150 +++++++++++++++++++++++++----------
> > 1 file changed, 108 insertions(+), 42 deletions(-)
> >
> > diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
> > index 48ab4684c3a5..6c522dec6967 100644
> > --- a/drivers/cpufreq/amd-pstate.c
> > +++ b/drivers/cpufreq/amd-pstate.c
> > @@ -65,6 +65,8 @@ static struct cpufreq_driver amd_pstate_epp_driver;
> > static int cppc_state = AMD_PSTATE_DISABLE;
> > struct kobject *amd_pstate_kobj;
> > +typedef int (*cppc_mode_transition_fn)(int);
> > +
> > static inline int get_mode_idx_from_str(const char *str, size_t size)
> > {
> > int i;
> > @@ -797,6 +799,105 @@ static ssize_t show_energy_performance_preference(
> > return sysfs_emit(buf, "%s\n", energy_perf_strings[preference]);
> > }
> > +static void amd_pstate_driver_cleanup(void)
> > +{
> > + amd_pstate_enable(false);
> > + cppc_state = AMD_PSTATE_DISABLE;
> > + current_pstate_driver = NULL;
> > +}
> > +
> > +static int amd_pstate_register_driver(int mode)
> > +{
> > + int ret;
> > +
> > + if (mode == AMD_PSTATE_PASSIVE || mode == AMD_PSTATE_GUIDED)
> > + current_pstate_driver = &amd_pstate_driver;
> > + else if (mode == AMD_PSTATE_ACTIVE)
> > + current_pstate_driver = &amd_pstate_epp_driver;
> > + else
> > + return -EINVAL;
> > +
> > + cppc_state = mode;
> > + ret = cpufreq_register_driver(current_pstate_driver);
> > + if (ret) {
> > + amd_pstate_driver_cleanup();
> > + return ret;
> > + }
> > + return 0;
> > +}
> > +
> > +static int amd_pstate_unregister_driver(int dummy)
> > +{
> > + int ret;
> > +
> > + ret = cpufreq_unregister_driver(current_pstate_driver);
> > +
> > + if (ret)
> > + return ret;
> > +
> > + amd_pstate_driver_cleanup();
> > + return 0;
> > +}
> > +
> > +static int amd_pstate_change_mode_without_dvr_change(int mode)
> > +{
> > + int cpu = 0;
> > +
> > + cppc_state = mode;
> > +
> > + if (boot_cpu_has(X86_FEATURE_CPPC) || cppc_state == AMD_PSTATE_ACTIVE)
> > + return 0;
> > +
> > + for_each_present_cpu(cpu) {
> > + cppc_set_auto_sel(cpu, (cppc_state == AMD_PSTATE_PASSIVE) ? 0 : 1);
> > + }
> > +
> > + return 0;
> > +}
> > +
> > +static int amd_pstate_change_driver_mode(int mode)
> > +{
> > + int ret;
> > +
> > + ret = amd_pstate_unregister_driver(0);
> > + if (ret)
> > + return ret;
> > +
> > + ret = amd_pstate_register_driver(mode);
> > + if (ret)
> > + return ret;
> > +
> > + return 0;
> > +}
> > +
> > +/* Mode transition table */
>
> This seems to be a pointless comment to me.
>
> > +cppc_mode_transition_fn mode_state_machine[AMD_PSTATE_MAX][AMD_PSTATE_MAX] = {
> > + [AMD_PSTATE_DISABLE] = {
> > + [AMD_PSTATE_DISABLE] = NULL,
> > + [AMD_PSTATE_PASSIVE] = amd_pstate_register_driver,
> > + [AMD_PSTATE_ACTIVE] = amd_pstate_register_driver,
> > + [AMD_PSTATE_GUIDED] = amd_pstate_register_driver,
> > + },
> > + [AMD_PSTATE_PASSIVE] = {
> > + [AMD_PSTATE_DISABLE] = amd_pstate_unregister_driver,
> > + [AMD_PSTATE_PASSIVE] = NULL,
> > + [AMD_PSTATE_ACTIVE] = amd_pstate_change_driver_mode,
> > + [AMD_PSTATE_GUIDED] = amd_pstate_change_mode_without_dvr_change,
> > + },
> > + [AMD_PSTATE_ACTIVE] = {
> > + [AMD_PSTATE_DISABLE] = amd_pstate_unregister_driver,
> > + [AMD_PSTATE_PASSIVE] = amd_pstate_change_driver_mode,
> > + [AMD_PSTATE_ACTIVE] = NULL,
> > + [AMD_PSTATE_GUIDED] = amd_pstate_change_driver_mode,
> > + },
> > + [AMD_PSTATE_GUIDED] = {
> > + [AMD_PSTATE_DISABLE] = amd_pstate_unregister_driver,
> > + [AMD_PSTATE_PASSIVE] = amd_pstate_change_mode_without_dvr_change,
> > + [AMD_PSTATE_ACTIVE] = amd_pstate_change_driver_mode,
> > + [AMD_PSTATE_GUIDED] = NULL,
> > + },
> > +};
> > +
> > static ssize_t amd_pstate_show_status(char *buf)
> > {
> > if (!current_pstate_driver)
> > @@ -805,57 +906,22 @@ static ssize_t amd_pstate_show_status(char *buf)
> > return sysfs_emit(buf, "%s\n", amd_pstate_mode_string[cppc_state]);
> > }
> > -static void amd_pstate_driver_cleanup(void)
> > -{
> > - current_pstate_driver = NULL;
> > -}
> > -
> > static int amd_pstate_update_status(const char *buf, size_t size)
> > {
> > - int ret;
> > int mode_idx;
> > - if (size > 7 || size < 6)
> > + if (size > strlen("passive") || size < strlen("active"))
> > return -EINVAL;
> > - mode_idx = get_mode_idx_from_str(buf, size);
> > - switch(mode_idx) {
> > - case AMD_PSTATE_DISABLE:
> > - if (!current_pstate_driver)
> > - return -EINVAL;
> > - if (cppc_state == AMD_PSTATE_ACTIVE)
> > - return -EBUSY;
> > - ret = cpufreq_unregister_driver(current_pstate_driver);
> > - amd_pstate_driver_cleanup();
> > - break;
> > - case AMD_PSTATE_PASSIVE:
> > - if (current_pstate_driver) {
> > - if (current_pstate_driver == &amd_pstate_driver)
> > - return 0;
> > - cpufreq_unregister_driver(current_pstate_driver);
> > - cppc_state = AMD_PSTATE_PASSIVE;
> > - current_pstate_driver = &amd_pstate_driver;
> > - }
> > + mode_idx = get_mode_idx_from_str(buf, size);
> > - ret = cpufreq_register_driver(current_pstate_driver);
> > - break;
> > - case AMD_PSTATE_ACTIVE:
> > - if (current_pstate_driver) {
> > - if (current_pstate_driver == &amd_pstate_epp_driver)
> > - return 0;
> > - cpufreq_unregister_driver(current_pstate_driver);
> > - current_pstate_driver = &amd_pstate_epp_driver;
> > - cppc_state = AMD_PSTATE_ACTIVE;
> > - }
> > + if (mode_idx < 0 || mode_idx >= AMD_PSTATE_MAX)
> > + return -EINVAL;
> > - ret = cpufreq_register_driver(current_pstate_driver);
> > - break;
> > - default:
> > - ret = -EINVAL;
> > - break;
> > - }
> > + if (mode_state_machine[cppc_state][mode_idx])
> > + return mode_state_machine[cppc_state][mode_idx](mode_idx);
> > - return ret;
> > + return -EBUSY;
> > }
> > static ssize_t show_status(struct kobject *kobj,
>
> With one nit fixed,
>
> Reviewed-by: Mario Limonciello <mario.limonciello@....com>
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