This is a note to let you know that I've just added the patch titled
pwm: lpc32xx: Don't modify HW state in .probe() after the PWM chip was registered
to the 4.9-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-lpc32xx-don-t-modify-hw-state-in-.probe-after-the-pwm-chip-was-registered.patch
and it can be found in the queue-4.9 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 3d2813fb17e5fd0d73c1d1442ca0192bde4af10e 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 18:27:49 +0200
Subject: pwm: lpc32xx: 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 3d2813fb17e5fd0d73c1d1442ca0192bde4af10e 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 set the default before.
(Side-note: I don't know what this register setting actually does, if
this modifies the polarity there is an inconsistency because the
inversed polarity isn't considered if the PWM is already running during
.probe().)
Fixes: acfd92fdfb93 ("pwm: lpc32xx: Set PWM_PIN_LEVEL bit to default value")
Cc: Sylvain Lemieux <slemieux@xxxxxxxxxxx>
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-lpc32xx.c | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)
--- a/drivers/pwm/pwm-lpc32xx.c
+++ b/drivers/pwm/pwm-lpc32xx.c
@@ -124,17 +124,17 @@ static int lpc32xx_pwm_probe(struct plat
lpc32xx->chip.npwm = 1;
lpc32xx->chip.base = -1;
+ /* If PWM is disabled, configure the output to the default value */
+ val = readl(lpc32xx->base + (lpc32xx->chip.pwms[0].hwpwm << 2));
+ val &= ~PWM_PIN_LEVEL;
+ writel(val, lpc32xx->base + (lpc32xx->chip.pwms[0].hwpwm << 2));
+
ret = pwmchip_add(&lpc32xx->chip);
if (ret < 0) {
dev_err(&pdev->dev, "failed to add PWM chip, error %d\n", ret);
return ret;
}
- /* When PWM is disable, configure the output to the default value */
- val = readl(lpc32xx->base + (lpc32xx->chip.pwms[0].hwpwm << 2));
- val &= ~PWM_PIN_LEVEL;
- writel(val, lpc32xx->base + (lpc32xx->chip.pwms[0].hwpwm << 2));
-
platform_set_drvdata(pdev, lpc32xx);
return 0;
Patches currently in stable-queue which might be from u.kleine-koenig@xxxxxxxxxxxxxx are
queue-4.9/pwm-mxs-don-t-modify-hw-state-in-.probe-after-the-pwm-chip-was-registered.patch
queue-4.9/pwm-lpc32xx-don-t-modify-hw-state-in-.probe-after-the-pwm-chip-was-registered.patch
