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Message-ID: <2f16fd5a59d6655ec9339473d516ac49c89e43f8.camel@intel.com>
Date: Wed, 14 Aug 2024 06:09:12 +0000
From: "Zhang, Rui" <rui.zhang@...el.com>
To: "linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>, "rjw@...ysocki.net"
<rjw@...ysocki.net>
CC: "lukasz.luba@....com" <lukasz.luba@....com>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"daniel.lezcano@...aro.org" <daniel.lezcano@...aro.org>, "peter@...e.net"
<peter@...e.net>
Subject: Re: [PATCH v1 4/4] thermal: gov_bang_bang: Use governor_data to
reduce overhead
On Tue, 2024-08-13 at 16:29 +0200, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
>
> After running once, the for_each_trip_desc() loop in
> bang_bang_manage() is pure needless overhead because it is not going
> to
> make any changes unless a new cooling device has been bound to one of
> the trips in the thermal zone or the system is resuming from sleep.
>
> For this reason, make bang_bang_manage() set governor_data for the
> thermal zone and check it upfront to decide whether or not it needs
> to
> do anything.
>
> However, governor_data needs to be reset in some cases to let
> bang_bang_manage() know that it should walk the trips again, so add
> an
> .update_tz() callback to the governor and make the core additionally
> invoke it during system resume.
>
> To avoid affecting the other users of that callback unnecessarily,
> add
> a special notification reason for system resume, THERMAL_TZ_RESUME,
> and
> also pass it to __thermal_zone_device_update() called during system
> resume for consistency.
>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> ---
> drivers/thermal/gov_bang_bang.c | 18 ++++++++++++++++++
> drivers/thermal/thermal_core.c | 3 ++-
> include/linux/thermal.h | 1 +
> 3 files changed, 21 insertions(+), 1 deletion(-)
>
> Index: linux-pm/drivers/thermal/gov_bang_bang.c
> ===================================================================
> --- linux-pm.orig/drivers/thermal/gov_bang_bang.c
> +++ linux-pm/drivers/thermal/gov_bang_bang.c
> @@ -86,6 +86,10 @@ static void bang_bang_manage(struct ther
> const struct thermal_trip_desc *td;
> struct thermal_instance *instance;
>
> + /* If the code below has run already, nothing needs to be
> done. */
> + if (tz->governor_data)
> + return;
> +
> for_each_trip_desc(tz, td) {
> const struct thermal_trip *trip = &td->trip;
>
> @@ -107,11 +111,25 @@ static void bang_bang_manage(struct ther
> bang_bang_set_instance_target(instanc
> e, 0);
> }
> }
> +
> + tz->governor_data = (void *)true;
> +}
> +
> +static void bang_bang_update_tz(struct thermal_zone_device *tz,
> + enum thermal_notify_event reason)
> +{
> + /*
> + * Let bang_bang_manage() know that it needs to walk trips
> after binding
> + * a new cdev and after system resume.
> + */
> + if (reason == THERMAL_TZ_BIND_CDEV || reason ==
> THERMAL_TZ_RESUME)
> + tz->governor_data = NULL;
> }
can we do the cdev initialization for BIND_CDEV and RESUME notification
in .update_tz() directly?
Then we don't need .manage() callback. This makes more sense to me
because bang_bang governor cares about trip point crossing only.
thanks,
rui
>
> static struct thermal_governor thermal_gov_bang_bang = {
> .name = "bang_bang",
> .trip_crossed = bang_bang_control,
> .manage = bang_bang_manage,
> + .update_tz = bang_bang_update_tz,
> };
> THERMAL_GOVERNOR_DECLARE(thermal_gov_bang_bang);
> Index: linux-pm/drivers/thermal/thermal_core.c
> ===================================================================
> --- linux-pm.orig/drivers/thermal/thermal_core.c
> +++ linux-pm/drivers/thermal/thermal_core.c
> @@ -1692,7 +1692,8 @@ static void thermal_zone_device_resume(s
>
> thermal_debug_tz_resume(tz);
> thermal_zone_device_init(tz);
> - __thermal_zone_device_update(tz, THERMAL_EVENT_UNSPECIFIED);
> + thermal_governor_update_tz(tz, THERMAL_TZ_RESUME);
> + __thermal_zone_device_update(tz, THERMAL_TZ_RESUME);
>
> complete(&tz->resume);
> tz->resuming = false;
> Index: linux-pm/include/linux/thermal.h
> ===================================================================
> --- linux-pm.orig/include/linux/thermal.h
> +++ linux-pm/include/linux/thermal.h
> @@ -55,6 +55,7 @@ enum thermal_notify_event {
> THERMAL_TZ_BIND_CDEV, /* Cooling dev is bind to the thermal
> zone */
> THERMAL_TZ_UNBIND_CDEV, /* Cooling dev is unbind from the
> thermal zone */
> THERMAL_INSTANCE_WEIGHT_CHANGED, /* Thermal instance weight
> changed */
> + THERMAL_TZ_RESUME, /* Thermal zone is resuming after system
> sleep */
> };
>
> /**
>
>
>
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