linux-kernel - [PATCH v1] PM: runtime: Unify error handling during suspend and resume

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Message-ID: <1922654.tdWV9SEqCh@rjwysocki.net>
Date: Thu, 20 Feb 2025 21:18:23 +0100
From: "Rafael J. Wysocki" <rjw@...ysocki.net>
To: Linux PM <linux-pm@...r.kernel.org>
Cc: LKML <linux-kernel@...r.kernel.org>,
 Alan Stern <stern@...land.harvard.edu>, Ulf Hansson <ulf.hansson@...aro.org>,
 Oliver Neukum <oneukum@...e.com>, Ajay Agarwal <ajayagarwal@...gle.com>,
 Brian Norris <briannorris@...gle.com>
Subject:
 [PATCH v1] PM: runtime: Unify error handling during suspend and resume

From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>

There is a confusing difference in error handling between rpm_suspend()
and rpm_resume() related to the special way in which the -EAGAIN and
-EBUSY error values are treated by the former.  Also, converting
-EACCES coming from the callback to an I/O error, which it quite likely
is not, may confuse runtime PM users a bit.

To address the above, modify rpm_callback() to convert -EACCES coming
from the driver to -EAGAIN and to set power.runtime_error only if the
return value is not -EAGAIN or -EBUSY.

This will cause the error handling in rpm_resume() and rpm_suspend() to
work consistently, so drop the no longer needed -EAGAIN or -EBUSY
special case from the latter and make it retry autosuspend if
power.runtime_error is unset.

Link: https://lore.kernel.org/linux-pm/20220620144231.GA23345@axis.com/
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
---
 drivers/base/power/runtime.c |   34 ++++++++++++++++++----------------
 1 file changed, 18 insertions(+), 16 deletions(-)

--- a/drivers/base/power/runtime.c
+++ b/drivers/base/power/runtime.c
@@ -448,8 +448,13 @@
 		retval = __rpm_callback(cb, dev);
 	}

-	dev->power.runtime_error = retval;
-	return retval != -EACCES ? retval : -EIO;
+	if (retval == -EACCES)
+		retval = -EAGAIN;
+
+	if (retval != -EAGAIN && retval != -EBUSY)
+		dev->power.runtime_error = retval;
+
+	return retval;
 }

 /**
@@ -725,21 +730,18 @@
 	dev->power.deferred_resume = false;
 	wake_up_all(&dev->power.wait_queue);

-	if (retval == -EAGAIN || retval == -EBUSY) {
-		dev->power.runtime_error = 0;
+	/*
+	 * On transient errors, if the callback routine failed an autosuspend,
+	 * and if the last_busy time has been updated so that there is a new
+	 * autosuspend expiration time, automatically reschedule another
+	 * autosuspend.
+	 */
+	if (!dev->power.runtime_error && (rpmflags & RPM_AUTO) &&
+	    pm_runtime_autosuspend_expiration(dev) != 0)
+		goto repeat;
+
+	pm_runtime_cancel_pending(dev);

-		/*
-		 * If the callback routine failed an autosuspend, and
-		 * if the last_busy time has been updated so that there
-		 * is a new autosuspend expiration time, automatically
-		 * reschedule another autosuspend.
-		 */
-		if ((rpmflags & RPM_AUTO) &&
-		    pm_runtime_autosuspend_expiration(dev) != 0)
-			goto repeat;
-	} else {
-		pm_runtime_cancel_pending(dev);
-	}
 	goto out;
 }