[Intel-gfx] Garbage on screen when switching resolution after BIOS post

[Daniel Vetter]

On Tue, Oct 04, 2011 at 05:53:08PM +0800, meteor wrote:
> We are developing a Linux solution. Our platform is using Intel SandyBridge
> and its VGA
> (kernel 2.6.35.8, 915 KMS driver).
> 
> We found system will show garbage at the moment VGA is hand over to OS after
> BIOS POST.
> The symptom doesn’t happen in WIN 7.
> After checking with EE, the LCD_VDD_EN pin is pull low again when boot to
> Win 7.
> However, this pin is not pull low when boot to Linux.
> 
> After BIOS POST, there’s a power reset during driver loading for resolution
> pattern sending.
> It’s why driver needs to control PCH "L_VDD_EN" for power reset, and the
> panel spec suggests to
> have VDD power off  for >=500ms.
> 
> Please refer to the VDD power monitoring image:
> http://imageshack.us/photo/my-images/827/auoi.jpg/
> 
> Need help to fix the issue in driver.

Sounds like you need Keith's eDP power sequencing rework. Afaik you can
grab the latest version here:

http://cgit.freedesktop.org/~keithp/linux/log/?h=macbook-air

Testing feedback highly welcome (and with some details about the panel
type/hw, if possible).

Yours, Daniel
-- 
Daniel Vetter
Mail: daniel at ffwll.ch
Mobile: +41 (0)79 365 57 48