linux-kernel - [PATCH 2/2] i2c: omap: wakeup the controller during suspend() callback

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Message-Id: <20240613-i2c-omap-wakeup-controller-during-suspend-v1-2-aab001eb1ad1@bootlin.com>
Date: Thu, 13 Jun 2024 15:13:28 +0200
From: Thomas Richard <thomas.richard@...tlin.com>
To: Vignesh R <vigneshr@...com>, Aaro Koskinen <aaro.koskinen@....fi>, 
 Janusz Krzysztofik <jmkrzyszt@...il.com>, Tony Lindgren <tony@...mide.com>, 
 Andi Shyti <andi.shyti@...nel.org>
Cc: linux-omap@...r.kernel.org, linux-i2c@...r.kernel.org, 
 linux-kernel@...r.kernel.org, gregory.clement@...tlin.com, 
 theo.lebrun@...tlin.com, thomas.petazzoni@...tlin.com, u-kumar1@...com, 
 Thomas Richard <thomas.richard@...tlin.com>, 
 Wolfram Sang <wsa+renesas@...g-engineering.com>
Subject: [PATCH 2/2] i2c: omap: wakeup the controller during suspend()
 callback

A device may need the controller up during suspend_noirq() or
resume_noirq().
But if the controller is autosuspended, there is no way to wakeup it during
suspend_noirq() or resume_noirq() because runtime pm is disabled at this
time.

The suspend() callback wakes up the controller, so it is available until
its suspend_noirq() callback (pm_runtime_force_suspend()).
During the resume, it's restored by resume_noirq() callback
(pm_runtime_force_resume()). Then resume() callback enables autosuspend.

So the controller is up during a little time slot in suspend and resume
sequences even if it's not used.

Reviewed-by: Andi Shyti <andi.shyti@...nel.org>
Acked-by: Wolfram Sang <wsa+renesas@...g-engineering.com>
Reviewed-by: Tony Lindgren <tony@...mide.com>
Signed-off-by: Thomas Richard <thomas.richard@...tlin.com>
---
 drivers/i2c/busses/i2c-omap.c | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/drivers/i2c/busses/i2c-omap.c b/drivers/i2c/busses/i2c-omap.c
index 410c8b37f768..35a3f0a64986 100644
--- a/drivers/i2c/busses/i2c-omap.c
+++ b/drivers/i2c/busses/i2c-omap.c
@@ -1574,9 +1574,31 @@ static int omap_i2c_runtime_resume(struct device *dev)
 	return 0;
 }
 
+static int omap_i2c_suspend(struct device *dev)
+{
+	/*
+	 * If the controller is autosuspended, there is no way to wakeup it once
+	 * runtime pm is disabled (in suspend_late()).
+	 * But a device may need the controller up during suspend_noirq() or
+	 * resume_noirq().
+	 * Wakeup the controller while runtime pm is enabled, so it is available
+	 * until its suspend_noirq(), and from resume_noirq().
+	 */
+	return pm_runtime_resume_and_get(dev);
+}
+
+static int omap_i2c_resume(struct device *dev)
+{
+	pm_runtime_mark_last_busy(dev);
+	pm_runtime_put_autosuspend(dev);
+
+	return 0;
+}
+
 static const struct dev_pm_ops omap_i2c_pm_ops = {
 	NOIRQ_SYSTEM_SLEEP_PM_OPS(pm_runtime_force_suspend,
 				  pm_runtime_force_resume)
+	SYSTEM_SLEEP_PM_OPS(omap_i2c_suspend, omap_i2c_resume)
 	RUNTIME_PM_OPS(omap_i2c_runtime_suspend,
 		       omap_i2c_runtime_resume, NULL)
 };

-- 
2.39.2