pwm: lpc32xx: Don't modify HW state in .probe() after the PWM chip was registered

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@tycoint.com>
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>

diff --git a/drivers/pwm/pwm-lpc32xx.c b/drivers/pwm/pwm-lpc32xx.c
index a9b3cff96aaca1c1a4429f58be7129fa82ec8827..ed8e9406b4af2568591b84962c5ef653c96717d9 100644 (file)
--- a/drivers/pwm/pwm-lpc32xx.c
+++ b/drivers/pwm/pwm-lpc32xx.c
@@ -124,17 +124,17 @@ static int lpc32xx_pwm_probe(struct platform_device *pdev)
        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;