On Thu, Apr 23, 2020 at 6:26 PM Douglas Anderson <dianders@xxxxxxxxxxxx> wrote: > People use panel-simple when they have panels that are builtin to > their device. In these cases the HPD (Hot Plug Detect) signal isn't > really used for hotplugging devices but instead is used for power > sequencing. Panel timing diagrams (especially for eDP panels) usually > have the HPD signal in them and it acts as an indicator that the panel > is ready for us to talk to it. > > Sometimes the HPD signal is hooked up to a normal GPIO on a system. > In this case we need to poll it in the correct place to know that the > panel is ready for us. In some system designs the right place for > this is panel-simple. > > When adding this support, we'll account for the case that there might > be a circular dependency between panel-simple and the provider of the > GPIO. The case this was designed for was for the "ti-sn65dsi86" > bridge chip. If HPD is hooked up to one of the GPIOs provided by the > bridge chip then in our probe function we'll always get back > -EPROBE_DEFER. Let's handle this by allowing this GPIO to show up > late if we saw -EPROBE_DEFER during probe. NOTE: since the > gpio_get_optional() is used, if the "hpd-gpios" isn't there our > variable will just be NULL and we won't do anything in prepare(). > > Signed-off-by: Douglas Anderson <dianders@xxxxxxxxxxxx> > Reviewed-by: Stephen Boyd <swboyd@xxxxxxxxxxxx> > --- > > Changes in v3: > - Remind how gpio_get_optional() works in the commit message. Reviewed-by: Linus Walleij <linus.walleij@xxxxxxxxxx> I have a small inkling to protest against calling this driver "panel-simple" as we tend to stockpile things like this. I suppose panel-panacea.c is a better name at this point :/ Yours, Linus Walleij
