From patchwork Wed Oct 24 13:52:46 2012 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: =?utf-8?q?Uwe_Kleine-K=C3=B6nig?= X-Patchwork-Id: 193788 Return-Path: X-Original-To: incoming-imx@patchwork.ozlabs.org Delivered-To: patchwork-incoming-imx@bilbo.ozlabs.org Received: from merlin.infradead.org (merlin.infradead.org [IPv6:2001:4978:20e::2]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by ozlabs.org (Postfix) with ESMTPS id A91BB2C008B for ; Thu, 25 Oct 2012 00:55:21 +1100 (EST) Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.76 #1 (Red Hat Linux)) id 1TR1OO-0003Bf-GH; Wed, 24 Oct 2012 13:53:08 +0000 Received: from metis.ext.pengutronix.de ([2001:6f8:1178:4:290:27ff:fe1d:cc33]) by merlin.infradead.org with esmtps (Exim 4.76 #1 (Red Hat Linux)) id 1TR1OK-0003AQ-EC for linux-arm-kernel@lists.infradead.org; Wed, 24 Oct 2012 13:53:05 +0000 Received: from dude.hi.pengutronix.de ([2001:6f8:1178:2:21e:67ff:fe11:9c5c]) by metis.ext.pengutronix.de with esmtp (Exim 4.72) (envelope-from ) id 1TR1OF-0007xj-No; Wed, 24 Oct 2012 15:52:59 +0200 Received: from ukl by dude.hi.pengutronix.de with local (Exim 4.80) (envelope-from ) id 1TR1OE-0004y1-ET; Wed, 24 Oct 2012 15:52:58 +0200 From: =?UTF-8?q?Uwe=20Kleine-K=C3=B6nig?= To: Thierry Reding , Shawn Guo , kernel@pengutronix.de Subject: [PATCH] RFC: leds-pwm: don't disable pwm when setting brightness to 0 Date: Wed, 24 Oct 2012 15:52:46 +0200 Message-Id: <1351086766-5837-1-git-send-email-u.kleine-koenig@pengutronix.de> X-Mailer: git-send-email 1.7.10.4 In-Reply-To: <20121024095603.GH639@pengutronix.de> References: <20121024095603.GH639@pengutronix.de> MIME-Version: 1.0 X-SA-Exim-Connect-IP: 2001:6f8:1178:2:21e:67ff:fe11:9c5c X-SA-Exim-Mail-From: ukl@pengutronix.de X-SA-Exim-Scanned: No (on metis.ext.pengutronix.de); SAEximRunCond expanded to false X-PTX-Original-Recipient: linux-arm-kernel@lists.infradead.org X-Spam-Note: CRM114 invocation failed X-Spam-Score: -2.6 (--) X-Spam-Report: SpamAssassin version 3.3.2 on merlin.infradead.org summary: Content analysis details: (-2.6 points) pts rule name description ---- ---------------------- -------------------------------------------------- -0.7 RP_MATCHES_RCVD Envelope sender domain matches handover relay domain -1.9 BAYES_00 BODY: Bayes spam probability is 0 to 1% [score: 0.0000] Cc: linux-kernel@vger.kernel.org, Richard Purdie , linux-arm-kernel@lists.infradead.org, Bryan Wu , Andrew Morton , linux-leds@vger.kernel.org X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.14 Precedence: list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: linux-arm-kernel-bounces@lists.infradead.org Errors-To: linux-arm-kernel-bounces+incoming-imx=patchwork.ozlabs.org@lists.infradead.org List-Id: linux-imx-kernel.lists.patchwork.ozlabs.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)