Re: [PATCH v2] pwm-backlight: fix the panel power sequence

YH Huang
2015-11-04T01:47:36Z

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);
else
gpiod_direction_output(pb->enable_gpio, 0);
}

And then update with props.brightness in backlight_update_status.
I am not sure, maybe I miss something.

Regards,
YH Huang