linux-kernel - [PATCH] PM: domains: Don't runtime resume devices at genpd

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Date:   Thu,  4 Mar 2021 20:28:43 +0100
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     "Rafael J . Wysocki" <rjw@...ysocki.net>, linux-pm@...r.kernel.org
Cc:     Lina Iyer <ilina@...eaurora.org>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Kevin Hilman <khilman@...nel.org>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Heiko Stuebner <heiko@...ech.de>,
        Matthias Brugger <matthias.bgg@...il.com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH] PM: domains: Don't runtime resume devices at genpd_prepare()

Runtime resuming a device upfront in the genpd_prepare() callback, to check
if there is a wakeup pending for it, seems like an unnecessary thing to do.
The PM core already manages these kind of things in a common way in
__device_suspend(), via calling pm_runtime_barrier() and
pm_wakeup_pending().

Therefore, let's simply drop this behaviour from genpd_prepare().

Note that, this change is applicable only for devices that are attached to
a genpd that has the GENPD_FLAG_ACTIVE_WAKEUP set (Renesas, Mediatek, and
Rockchip platforms). Moreover, a driver that needs to restore power for its
device to re-configure it for a system wakeup, may still call
pm_runtime_get_sync(), for example, to do this.

Signed-off-by: Ulf Hansson <ulf.hansson@...aro.org>
---
 drivers/base/power/domain.c | 36 ------------------------------------
 1 file changed, 36 deletions(-)

diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
index 78c310d3179d..b6a782c31613 100644
--- a/drivers/base/power/domain.c
+++ b/drivers/base/power/domain.c
@@ -1087,34 +1087,6 @@ static void genpd_sync_power_on(struct generic_pm_domain *genpd, bool use_lock,
 	genpd->status = GENPD_STATE_ON;
 }
 
-/**
- * resume_needed - Check whether to resume a device before system suspend.
- * @dev: Device to check.
- * @genpd: PM domain the device belongs to.
- *
- * There are two cases in which a device that can wake up the system from sleep
- * states should be resumed by genpd_prepare(): (1) if the device is enabled
- * to wake up the system and it has to remain active for this purpose while the
- * system is in the sleep state and (2) if the device is not enabled to wake up
- * the system from sleep states and it generally doesn't generate wakeup signals
- * by itself (those signals are generated on its behalf by other parts of the
- * system).  In the latter case it may be necessary to reconfigure the device's
- * wakeup settings during system suspend, because it may have been set up to
- * signal remote wakeup from the system's working state as needed by runtime PM.
- * Return 'true' in either of the above cases.
- */
-static bool resume_needed(struct device *dev,
-			  const struct generic_pm_domain *genpd)
-{
-	bool active_wakeup;
-
-	if (!device_can_wakeup(dev))
-		return false;
-
-	active_wakeup = genpd_is_active_wakeup(genpd);
-	return device_may_wakeup(dev) ? active_wakeup : !active_wakeup;
-}
-
 /**
  * genpd_prepare - Start power transition of a device in a PM domain.
  * @dev: Device to start the transition of.
@@ -1135,14 +1107,6 @@ static int genpd_prepare(struct device *dev)
 	if (IS_ERR(genpd))
 		return -EINVAL;
 
-	/*
-	 * If a wakeup request is pending for the device, it should be woken up
-	 * at this point and a system wakeup event should be reported if it's
-	 * set up to wake up the system from sleep states.
-	 */
-	if (resume_needed(dev, genpd))
-		pm_runtime_resume(dev);
-
 	genpd_lock(genpd);
 
 	if (genpd->prepared_count++ == 0)
-- 
2.25.1