Hello,

On Mon, Apr 24, 2023 at 03:16:34AM +0530, Naresh Kamboju wrote:

Following build errors noticed on arm64 and arm while building stable-rc 5.4.

Reported-by: Linux Kernel Functional Testing lkft@linaro.org

Build error:

drivers/pwm/pwm-meson.c: In function 'meson_pwm_apply': drivers/pwm/pwm-meson.c:313:25: error: assignment of member 'polarity' in read-only object 313 | state->polarity = PWM_POLARITY_NORMAL; | ^ make[3]: *** [scripts/Makefile.build:262: drivers/pwm/pwm-meson.o] Error 1 make[3]: Target '__build' not remade because of errors. make[2]: *** [scripts/Makefile.build:497: drivers/pwm] Error 2

Suspected commit:

pwm: meson: Explicitly set .polarity in .get_state() commit 8caa81eb950cb2e9d2d6959b37d853162d197f57 upstream.

Thanks for the report. I sent a fix to that patch in reply to the patch being announced to be picked for 5.4.y, but failed to Cc you. I just replied to the mail, so it didn't even go to stable@vger.kernel.org.

For reference, here comes the fixed patch again, see below.

Best regards Uwe

------->8-------- From: Uwe Kleine-König u.kleine-koenig@pengutronix.de Date: Wed, 22 Mar 2023 22:45:44 +0100 Subject: [PATCH] pwm: meson: Explicitly set .polarity in .get_state()

[ 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.

Fixes: c375bcbaabdb ("pwm: meson: Read the full hardware state in meson_pwm_get_state()") Reported-by: Munehisa Kamata kamatam@amazon.com Acked-by: Martin Blumenstingl martin.blumenstingl@googlemail.com Link: https://lore.kernel.org/r/20230310191405.2606296-1-u.kleine-koenig@pengutron... Signed-off-by: Uwe Kleine-König u.kleine-koenig@pengutronix.de Signed-off-by: Thierry Reding thierry.reding@gmail.com Signed-off-by: Uwe Kleine-König u.kleine-koenig@pengutronix.de --- drivers/pwm/pwm-meson.c | 7 +++++++ 1 file changed, 7 insertions(+)

diff --git a/drivers/pwm/pwm-meson.c b/drivers/pwm/pwm-meson.c index 6245bbdb6e6c..3c81858a8261 100644 --- a/drivers/pwm/pwm-meson.c +++ b/drivers/pwm/pwm-meson.c @@ -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 = {