Re: [PATCH] CHROMIUM: i915: Initialize panel timing registers if VBIOS did not.

[Jesse Barnes <jbarnes@virtuousgeek.org>]

I don't think 0 is a reasonable value for any of those fields, so
checking them against 0 should be fine.

Jesse

On Thu, 7 Oct 2010 16:48:51 -0700
Bryan Freed <bfreed@chromium.org> wrote:

> My change tries to detect the lack of initialization by A) finding no VBT,
> and B) finding 0 values in these registers.
> 
> But what if there is a VBIOS out there that really wants these values to be
> 0?  I provide for that case by checking for VBT.
> 
> Is this a reasonable case?  If not, I have no problem moving the check
> to init_vbt_default().
> 
> bryan.
> 
> On Thu, Oct 7, 2010 at 3:55 PM, Chris Wilson <chris@chris-wilson.co.uk>wrote:
> 
> > On Thu, 7 Oct 2010 15:48:14 -0700, Bryan Freed <bfreed@chromium.org>
> > wrote:
> > > The time between start of the pixel clock and backlight enable is a basic
> > > panel timing constraint.  If no VBIOS Table is found, and the Panel Power
> > > On/Off registers are found to be 0, assume we are booting without VBIOS
> > > initialization and set these registers to something reasonable.
> >
> > IIRC, the panel sequence registers are meant to be stored in the VBIOS. So
> > if we add the parsing of those to the driver and add the defaults to
> > init_vbt_default() then we can check whether PP_ON_DELAYS is valid upon
> > device init (module load and resume) and fixup in case the BIOS does not.
> > -Chris
> >
> > --
> > Chris Wilson, Intel Open Source Technology Centre
> >


-- 
Jesse Barnes, Intel Open Source Technology Center