From: Uwe Kleine-König u.kleine-koenig@pengutronix.de
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@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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- 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 @@ -152,6 +152,11 @@ 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); @@ -160,15 +165,7 @@ 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)