This is a note to let you know that I've just added the patch titled
pwm: mxs: Don't modify HW state in .probe() after the PWM chip was registered
to the 4.4-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-mxs-don-t-modify-hw-state-in-.probe-after-the-pwm-chip-was-registered.patch
and it can be found in the queue-4.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 020162d6f49f2963062229814a56a89c86cbeaa8 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Uwe=20Kleine-K=C3=B6nig?= <u.kleine-koenig@xxxxxxxxxxxxxx>
Date: Wed, 7 Jul 2021 18:27:50 +0200
Subject: pwm: mxs: Don't modify HW state in .probe() after the PWM chip was registered
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From: Uwe Kleine-König <u.kleine-koenig@xxxxxxxxxxxxxx>
commit 020162d6f49f2963062229814a56a89c86cbeaa8 upstream.
This fixes a race condition: After pwmchip_add() is called there might
already be a consumer and then modifying the hardware behind the
consumer's back is bad. So reset before calling pwmchip_add().
Note that reseting the hardware isn't the right thing to do if the PWM
is already running as it might e.g. disable (or even enable) a backlight
that is supposed to be on (or off).
Fixes: 4dce82c1e840 ("pwm: add pwm-mxs support")
Cc: Sascha Hauer <s.hauer@xxxxxxxxxxxxxx>
Cc: Shawn Guo <shawnguo@xxxxxxxxxx>
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@xxxxxxxxxxxxxx>
Signed-off-by: Thierry Reding <thierry.reding@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/pwm/pwm-mxs.c | 13 +++++--------
1 file changed, 5 insertions(+), 8 deletions(-)
--- a/drivers/pwm/pwm-mxs.c
+++ b/drivers/pwm/pwm-mxs.c
@@ -158,6 +158,11 @@ static int mxs_pwm_probe(struct platform
return ret;
}
+ /* FIXME: Only do this if the PWM isn't already running */
+ ret = stmp_reset_block(mxs->base);
+ if (ret)
+ return dev_err_probe(&pdev->dev, ret, "failed to reset PWM\n");
+
ret = pwmchip_add(&mxs->chip);
if (ret < 0) {
dev_err(&pdev->dev, "failed to add pwm chip %d\n", ret);
@@ -166,15 +171,7 @@ static int mxs_pwm_probe(struct platform
platform_set_drvdata(pdev, mxs);
- ret = stmp_reset_block(mxs->base);
- if (ret)
- goto pwm_remove;
-
return 0;
-
-pwm_remove:
- pwmchip_remove(&mxs->chip);
- return ret;
}
static int mxs_pwm_remove(struct platform_device *pdev)
Patches currently in stable-queue which might be from u.kleine-koenig@xxxxxxxxxxxxxx are
queue-4.4/pwm-mxs-don-t-modify-hw-state-in-.probe-after-the-pwm-chip-was-registered.patch
