Hi On Thu, Feb 2, 2017 at 3:38 PM, Douglas Anderson <dianders@xxxxxxxxxxxx> wrote: > The Sharp lq123p1jx31 has a requirement that the VDD is on for at > least 300 ms before being turned off. At the moment nothing anywhere > in the kernel is ensuring this. > > The simplest way to ensure this is to add a "disable" timing of 150 > ms. With this the we know that there will be at least 300 ms between > the regulator/gpio being turned on and being turned off. > Specifically, here's what happens after this change: > > * prepare: enable regulator, delay 110 ms (10 for regulator, then 100) > * enable: delay 50 ms > * disable: delay 150 ms, then disable regulator > * unprepare: delay 550 ms (50 for regulator, 500 to off=>on too quick) > > As you can see, even giving the regulator 10 ms (the max the panel > spec allows) for ramping up we are sure that the regulator was on for > 300 ms now. > > Signed-off-by: Douglas Anderson <dianders@xxxxxxxxxxxx> > --- > drivers/gpu/drm/panel/panel-simple.c | 1 + > 1 file changed, 1 insertion(+) NAKing my own patch. While this patch _does_ indeed enforce a requirement from the datasheet and also empirically fixes the problem I was seeing, I'm nearly certain that the reason it works has more to do with luck than anything else. After a little more digging, I'm becoming more certain that we need to manage the backlight state for this panel and sequence it properly with the enable signals. Assuming this is correct, I will likely post another patch adding a custom panel driver. -Doug _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
