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pwm: mxs: Don't modify HW state in .probe() after the PWM chip was registered 

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: 4dce82c1e8 ("pwm: add pwm-mxs support")
Cc: Sascha Hauer <s.hauer@pengutronix.de>
Cc: Shawn Guo <shawnguo@kernel.org>
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
This commit is contained in:
Uwe Kleine-König 2021-07-07 18:27:50 +02:00 committed by Thierry Reding
parent 3d2813fb17
commit 020162d6f4
1 changed files with 5 additions and 8 deletions
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13
drivers/pwm/pwm-mxs.c
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@ -145,6 +145,11 @@ static int mxs_pwm_probe(struct platform_device *pdev)
return ret; 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); ret = pwmchip_add(&mxs->chip);
if (ret < 0) { if (ret < 0) {
dev_err(&pdev->dev, "failed to add pwm chip %d\n", ret); dev_err(&pdev->dev, "failed to add pwm chip %d\n", ret);
@ -153,15 +158,7 @@ static int mxs_pwm_probe(struct platform_device *pdev)
platform_set_drvdata(pdev, mxs); platform_set_drvdata(pdev, mxs);
ret = stmp_reset_block(mxs->base);
if (ret)
goto pwm_remove;
return 0; return 0;
pwm_remove:
pwmchip_remove(&mxs->chip);
return ret;
} }
static int mxs_pwm_remove(struct platform_device *pdev) static int mxs_pwm_remove(struct platform_device *pdev)