From patchwork Wed Oct 24 13:52:46 2012 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Subject: RFC: leds-pwm: don't disable pwm when setting brightness to 0 Date: Wed, 24 Oct 2012 03:52:46 -0000 From: =?utf-8?q?Uwe_Kleine-K=C3=B6nig?= X-Patchwork-Id: 193788 Message-Id: <1351086766-5837-1-git-send-email-u.kleine-koenig@pengutronix.de> To: Thierry Reding , Shawn Guo , kernel@pengutronix.de Cc: linux-kernel@vger.kernel.org, Richard Purdie , linux-arm-kernel@lists.infradead.org, Bryan Wu , Andrew Morton , linux-leds@vger.kernel.org This fixes disabling the LED on i.MX28. The PWM hardware delays using the newly set pwm-config until the beginning of a new period. It's very likely that pwm_disable is called before the current period ends. In case the LED was on brightness=max before the LED stays on because in the disabled PWM block the period never ends. It's unclear if the mxs-pwm driver doesn't implement the API as expected (i.e. it should block until the newly set config is effective) or if the leds-pwm driver makes wrong assumptions. This patch assumes the latter. Signed-off-by: Uwe Kleine-König --- Hello, I'm not sure this is correct, but this is the workaround I'm using until I get some feed back. Best regards Uwe drivers/leds/leds-pwm.c | 9 ++------- 1 file changed, 2 insertions(+), 7 deletions(-) diff --git a/drivers/leds/leds-pwm.c b/drivers/leds/leds-pwm.c index f2e44c7..a909f4f 100644 --- a/drivers/leds/leds-pwm.c +++ b/drivers/leds/leds-pwm.c @@ -38,13 +38,8 @@ static void led_pwm_set(struct led_classdev *led_cdev, unsigned int max = led_dat->cdev.max_brightness; unsigned int period = led_dat->period; - if (brightness == 0) { - pwm_config(led_dat->pwm, 0, period); - pwm_disable(led_dat->pwm); - } else { - pwm_config(led_dat->pwm, brightness * period / max, period); - pwm_enable(led_dat->pwm); - } + pwm_config(led_dat->pwm, brightness * period / max, period); + pwm_enable(led_dat->pwm); } static int led_pwm_probe(struct platform_device *pdev)