From mboxrd@z Thu Jan 1 00:00:00 1970 From: Philipp Zabel Date: Thu, 05 Nov 2015 09:40:30 +0000 Subject: Re: [PATCH v2] pwm-backlight: fix the panel power sequence Message-Id: <1446716430.3894.12.camel@pengutronix.de> List-Id: References: <1444987060-48202-1-git-send-email-yh.huang@mediatek.com> <1444988219.3541.3.camel@pengutronix.de> <1445526750.27586.8.camel@mtksdaap41> <1446133259.3274.52.camel@pengutronix.de> <1446190900.17558.16.camel@mtksdaap41> <1446201271.3334.22.camel@pengutronix.de> <1446538299.2449.8.camel@mtksdaap41> <1446548924.3373.3.camel@pengutronix.de> <1446601656.15340.11.camel@mtksdaap41> In-Reply-To: <1446601656.15340.11.camel@mtksdaap41> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-arm-kernel@lists.infradead.org Am Mittwoch, den 04.11.2015, 09:47 +0800 schrieb YH Huang: > On Tue, 2015-11-03 at 12:08 +0100, Philipp Zabel wrote: > > Hi YH, > > > > Am Dienstag, den 03.11.2015, 16:11 +0800 schrieb YH Huang: > > > > The reasoning is that devices where there is no phandle link pointing to > > > > the backlight (for example from a simple-panel node), we should keep the > > > > current default behaviour (enable during probe). > > > > > > I have a little problem for the current default behaviour. > > > Should we enable during probe? > > > > Here I mean enabling the backlight (at the end of the probe function), > > not enabling the GPIO already when requesting it. > > > > > Before this patch ( http://patchwork.ozlabs.org/patch/324690/ ), > > > we disable "enable-gpio" in the probe function. > > > > While before this patch the GPIO would be initialized in the disabled > > state, the call to backlight_update_status at the end of the probe > > function would still enable the backlight afterwards. > > Based on this, could we disable it initially and update in the > backlight_update_status function? > > Like this, > > if (pb->enable_gpio) { > if (phandle && > gpiod_get_direction(pb->enable_gpio) = GPIOF_DIR_OUT && > gpiod_get_value(pb->enable_gpio) = 1) > gpiod_direction_output(pb->enable_gpio, 1); The gpiod_direction_output call is a no-op, since the direction is already output and the value is already 1. Also, I propose to set initial blanking to FB_BLANK_POWERDOWN in this case, and wait for the panel driver to enable the backlight at the appropriate time. regards Philipp