Hi
On Thu, Feb 2, 2017 at 3:38 PM, Douglas Anderson dianders@chromium.org 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@chromium.org
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