FAILED: patch "[PATCH] pwm: meson: Explicitly set .polarity in .get_state()" failed to apply to 5.10-stable tree

The patch below does not apply to the 5.10-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.10.y
git checkout FETCH_HEAD
git cherry-pick -x 8caa81eb950cb2e9d2d6959b37d853162d197f57
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2023042242-unsaved-sanded-d4c1@gregkh' --subject-prefix 'PATCH 5.10.y' HEAD^..

Possible dependencies:

8caa81eb950c ("pwm: meson: Explicitly set .polarity in .get_state()")
6c452cff79f8 ("pwm: Make .get_state() callback return an error code")
8eca6b0a647a ("Merge tag 'pwm/for-5.19-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/thierry.reding/linux-pwm")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 8caa81eb950cb2e9d2d6959b37d853162d197f57 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Uwe=20Kleine-K=C3=B6nig?= <[email protected]>
Date: Wed, 22 Mar 2023 22:45:44 +0100
Subject: [PATCH] pwm: meson: Explicitly set .polarity in .get_state()
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

The driver only supports normal polarity. Complete the implementation of .get_state() by setting .polarity accordingly.

This fixes a regression that was possible since commit c73a3107624d ("pwm: Handle .get_state() failures") which stopped to zero-initialize the state passed to the .get_state() callback. This was reported at
https://forum.odroid.com/viewtopic.php?f=177&t=46360 . While this was an unintended side effect, the real issue is the driver's callback not setting the polarity.

There is a complicating fact, that the .apply() callback fakes support for inversed polarity. This is not (and cannot) be matched by .get_state(). As fixing this isn't easy, only point it out in a comment to prevent authors of other drivers from copying that approach.

index 16d79ca5d8f5..5cd7b90872c6 100644
@@ -162,6 +162,12 @@ static int meson_pwm_calc(struct meson_pwm *meson, struct pwm_device *pwm,
 	duty = state->duty_cycle;
 	period = state->period;
 
+	/*
+	 * Note this is wrong. The result is an output wave that isn't really
+	 * inverted and so is wrongly identified by .get_state as normal.
+	 * Fixing this needs some care however as some machines might rely on
+	 * this.
+	 */
 	if (state->polarity == PWM_POLARITY_INVERSED)
 		duty = period - duty;
 

@@ -358,6 +364,8 @@ static int meson_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
 		state->duty_cycle = 0;
 	}
 
+	state->polarity = PWM_POLARITY_NORMAL;
+
 	return 0;
 }
 

[ Upstream commit 8caa81eb950cb2e9d2d6959b37d853162d197f57 ]

The driver only supports normal polarity. Complete the implementation of .get_state() by setting .polarity accordingly.

This fixes a regression that was possible since commit c73a3107624d ("pwm: Handle .get_state() failures") which stopped to zero-initialize the state passed to the .get_state() callback. This was reported at
https://forum.odroid.com/viewtopic.php?f=177&t=46360 . While this was an unintended side effect, the real issue is the driver's callback not setting the polarity.

There is a complicating fact, that the .apply() callback fakes support for inversed polarity. This is not (and cannot) be matched by .get_state(). As fixing this isn't easy, only point it out in a comment to prevent authors of other drivers from copying that approach.

---
 drivers/pwm/pwm-meson.c | 7 +++++++
 1 file changed, 7 insertions(+)

index bd0d7336b898..237bb8e06593 100644
@@ -168,6 +168,12 @@ static int meson_pwm_calc(struct meson_pwm *meson, struct pwm_device *pwm,
 	duty = state->duty_cycle;
 	period = state->period;
 
+	/*
+	 * Note this is wrong. The result is an output wave that isn't really
+	 * inverted and so is wrongly identified by .get_state as normal.
+	 * Fixing this needs some care however as some machines might rely on
+	 * this.
+	 */
 	if (state->polarity == PWM_POLARITY_INVERSED)
 		duty = period - duty;
 

@@ -366,6 +372,7 @@ static void meson_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
 		state->period = 0;
 		state->duty_cycle = 0;
 	}
+	state->polarity = PWM_POLARITY_NORMAL;
 }
 
 static const struct pwm_ops meson_pwm_ops = {

2.39.2