From mboxrd@z Thu Jan 1 00:00:00 1970 From: Philipp Zabel Subject: [PATCH v5] pwm-backlight: Avoid backlight flicker when probed from DT Date: Wed, 18 Nov 2015 18:12:25 +0100 Message-ID: <1447866745-21567-1-git-send-email-p.zabel@pengutronix.de> Return-path: Received: from metis.ext.4.pengutronix.de ([92.198.50.35]:42007 "EHLO metis.ext.pengutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756487AbbKRRMi (ORCPT ); Wed, 18 Nov 2015 12:12:38 -0500 Sender: linux-pwm-owner@vger.kernel.org List-Id: linux-pwm@vger.kernel.org To: Thierry Reding , Jingoo Han , Lee Jones Cc: Ajay Kumar , YH Huang , Christian Gmeiner , Heiko Stuebner , linux-pwm@vger.kernel.org, linux-fbdev@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kernel@pengutronix.de, Philipp Zabel If the driver is probed from the device tree, and there is a phandle property set on it, and the enable GPIO is already configured as output, and the backlight is currently disabled, keep it disabled. If all these conditions are met, assume there will be some other driver that can enable the backlight at the appropriate time. Signed-off-by: Philipp Zabel Reviewed-by: Christian Gmeiner Tested-by: Heiko Stuebner --- - Rebased onto v4.4-rc1 - Added Heiko's Tested-by --- drivers/video/backlight/pwm_bl.c | 23 ++++++++++++++++++++++- 1 file changed, 22 insertions(+), 1 deletion(-) diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c index ae3c6b6..3daf9cc 100644 --- a/drivers/video/backlight/pwm_bl.c +++ b/drivers/video/backlight/pwm_bl.c @@ -199,6 +199,8 @@ static int pwm_backlight_probe(struct platform_device *pdev) struct backlight_properties props; struct backlight_device *bl; struct pwm_bl_data *pb; + phandle phandle = pdev->dev.of_node->phandle; + int initial_blank = FB_BLANK_UNBLANK; int ret; if (!data) { @@ -242,7 +244,7 @@ static int pwm_backlight_probe(struct platform_device *pdev) pb->enabled = false; pb->enable_gpio = devm_gpiod_get_optional(&pdev->dev, "enable", - GPIOD_OUT_HIGH); + GPIOD_ASIS); if (IS_ERR(pb->enable_gpio)) { ret = PTR_ERR(pb->enable_gpio); goto err_alloc; @@ -264,12 +266,30 @@ static int pwm_backlight_probe(struct platform_device *pdev) pb->enable_gpio = gpio_to_desc(data->enable_gpio); } + if (pb->enable_gpio) { + /* + * If the driver is probed from the device tree and there is a + * phandle link pointing to the backlight node, it is safe to + * assume that another driver will enable the backlight at the + * appropriate time. Therefore, if it is disabled, keep it so. + */ + if (phandle && + gpiod_get_direction(pb->enable_gpio) == GPIOF_DIR_OUT && + gpiod_get_value(pb->enable_gpio) == 0) + initial_blank = FB_BLANK_POWERDOWN; + else + gpiod_direction_output(pb->enable_gpio, 1); + } + pb->power_supply = devm_regulator_get(&pdev->dev, "power"); if (IS_ERR(pb->power_supply)) { ret = PTR_ERR(pb->power_supply); goto err_alloc; } + if (phandle && !regulator_is_enabled(pb->power_supply)) + initial_blank = FB_BLANK_POWERDOWN; + pb->pwm = devm_pwm_get(&pdev->dev, NULL); if (IS_ERR(pb->pwm) && PTR_ERR(pb->pwm) != -EPROBE_DEFER && !pdev->dev.of_node) { @@ -320,6 +340,7 @@ static int pwm_backlight_probe(struct platform_device *pdev) } bl->props.brightness = data->dft_brightness; + bl->props.power = initial_blank; backlight_update_status(bl); platform_set_drvdata(pdev, bl); -- 2.6.2