On Thu, Sep 22, 2016 at 08:03:31AM +1000, Jonathan Liu wrote:
> Hi Maxime,
>
> On Thursday, 22 September 2016, Maxime Ripard <maxime.ripard at
> free-electrons.
> com> wrote:
>
> > On Wed, Sep 21, 2016 at 11:03:04PM +1000, Jonathan Liu wrote:
> > > The panel should be enabled after the controller so that the panel
> > > prepare/enable delays are properly taken into account. Similarly, the
> > > panel should be disabled before the controller so that the panel
> > > unprepare/disable delays are properly taken into account.
> > >
> > > This is useful for avoiding visual glitches.
> >
> > This is not really taking any delays into account, especially since
> > drm_panel_enable and prepare are suppose to block until their
> > operation is complete.
>
>
> drm_panel_prepare turns on power to the LCD using enable-gpios property of
> the panel and then blocks for prepare delay. The prepare delay for panel
> can be set to how long it takes between the time the panel is powered to
> when it is ready to receive images. If backlight property is specified the
> backlight will be off while the panel is powered on.
>
> drm_panel_enable blocks for enable delay and then turns on the backlight.
> The enable delay can be set to how long it takes for panel to start making
> the image visible after receiving the first valid frame. For example if the
> panel starts off as white and the TFT takes some time to initialize to
> black before it shows the image being received.
>
> Refer to drivers/gpu/drm/panel-panel.simple.c for details.
