linux-kernel - [PATCH] PM: runtime: Have devm_pm_runtime_enable() handle pm_runtime_dont_use

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Date:   Wed, 23 Feb 2022 08:34:48 -0800
From:   Douglas Anderson <dianders@...omium.org>
To:     "Rafael J . Wysocki" <rafael@...nel.org>
Cc:     Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Stephen Boyd <sboyd@...nel.org>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Douglas Anderson <dianders@...omium.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>,
        linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org
Subject: [PATCH] PM: runtime: Have devm_pm_runtime_enable() handle pm_runtime_dont_use_autosuspend()

The PM Runtime docs say:
  Drivers in ->remove() callback should undo the runtime PM changes done
  in ->probe(). Usually this means calling pm_runtime_disable(),
  pm_runtime_dont_use_autosuspend() etc.

>From grepping code, it's clear that many people aren't aware of the
need to call pm_runtime_dont_use_autosuspend().

When brainstorming solutions, one idea that came up was to leverage
the new-ish devm_pm_runtime_enable() function. The idea here is that:
* When the devm action is called we know that the driver is being
  removed. It's the perfect time to undo the use_autosuspend.
* The code of pm_runtime_dont_use_autosuspend() already handles the
  case of being called when autosuspend wasn't enabled.

Suggested-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>
Signed-off-by: Douglas Anderson <dianders@...omium.org>
---

 drivers/base/power/runtime.c | 5 +++++
 include/linux/pm_runtime.h   | 4 ++++
 2 files changed, 9 insertions(+)

diff --git a/drivers/base/power/runtime.c b/drivers/base/power/runtime.c
index 2f3cce17219b..d4059e6ffeae 100644
--- a/drivers/base/power/runtime.c
+++ b/drivers/base/power/runtime.c
@@ -1476,11 +1476,16 @@ EXPORT_SYMBOL_GPL(pm_runtime_enable);
 
 static void pm_runtime_disable_action(void *data)
 {
+	pm_runtime_dont_use_autosuspend(data);
 	pm_runtime_disable(data);
 }
 
 /**
  * devm_pm_runtime_enable - devres-enabled version of pm_runtime_enable.
+ *
+ * NOTE: this will also handle calling pm_runtime_dont_use_autosuspend() for
+ * you at driver exit time if needed.
+ *
  * @dev: Device to handle.
  */
 int devm_pm_runtime_enable(struct device *dev)
diff --git a/include/linux/pm_runtime.h b/include/linux/pm_runtime.h
index 9f09601c465a..2bff6a10095d 100644
--- a/include/linux/pm_runtime.h
+++ b/include/linux/pm_runtime.h
@@ -567,6 +567,10 @@ static inline void pm_runtime_disable(struct device *dev)
  * Allow the runtime PM autosuspend mechanism to be used for @dev whenever
  * requested (or "autosuspend" will be handled as direct runtime-suspend for
  * it).
+ *
+ * NOTE: It's important to undo this with pm_runtime_dont_use_autosuspend()
+ * at driver exit time unless your driver initially enabled pm_runtime
+ * with devm_pm_runtime_enable() (which handles it for you).
  */
 static inline void pm_runtime_use_autosuspend(struct device *dev)
 {
-- 
2.35.1.473.g83b2b277ed-goog