This is a note to let you know that I've just added the patch titled
pwm: meson: Explicitly set .polarity in .get_state()
to the 5.10-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
pwm-meson-explicitly-set-.polarity-in-.get_state.patch
and it can be found in the queue-5.10 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 8caa81eb950cb2e9d2d6959b37d853162d197f57 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Uwe=20Kleine-K=C3=B6nig?= <u.kleine-koenig@xxxxxxxxxxxxxx>
Date: Wed, 22 Mar 2023 22:45:44 +0100
Subject: pwm: meson: Explicitly set .polarity in .get_state()
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
From: Uwe Kleine-König <u.kleine-koenig@xxxxxxxxxxxxxx>
commit 8caa81eb950cb2e9d2d6959b37d853162d197f57 upstream.
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.
Fixes: c375bcbaabdb ("pwm: meson: Read the full hardware state in meson_pwm_get_state()")
Reported-by: Munehisa Kamata <kamatam@xxxxxxxxxx>
Acked-by: Martin Blumenstingl <martin.blumenstingl@xxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20230310191405.2606296-1-u.kleine-koenig@xxxxxxxxxxxxxx
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@xxxxxxxxxxxxxx>
Signed-off-by: Thierry Reding <thierry.reding@xxxxxxxxx>
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@xxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/pwm/pwm-meson.c | 7 +++++++
1 file changed, 7 insertions(+)
--- a/drivers/pwm/pwm-meson.c
+++ b/drivers/pwm/pwm-meson.c
@@ -168,6 +168,12 @@ static int meson_pwm_calc(struct meson_p
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 p
state->period = 0;
state->duty_cycle = 0;
}
+ state->polarity = PWM_POLARITY_NORMAL;
}
static const struct pwm_ops meson_pwm_ops = {
Patches currently in stable-queue which might be from u.kleine-koenig@xxxxxxxxxxxxxx are
queue-5.10/pwm-meson-explicitly-set-.polarity-in-.get_state.patch
