Re: PROBLEM: Intel VGA output busticated on 4.3-rc2 (regression)

From: Nick Bowler
Date: Wed Oct 07 2015 - 10:29:27 EST


On 10/7/15, Ville SyrjÃlà <ville.syrjala@xxxxxxxxxxxxxxx> wrote:
> On Tue, Oct 06, 2015 at 11:42:33AM -0400, Nick Bowler wrote:
>> On 9/24/15, Nick Bowler <nbowler@xxxxxxxxxx> wrote:
>> > Testing out 4.3-rc2, first thing I notice is that the VGA output is
>> > not working. Specifically, the display is continuously powering on
>> > and off -- at no point is any image visible on the screen (I am
>> > expecting to see the console output). The display connected to the
>> > HDMI output is working fine.
[...]
>> b8afb9113c519a8bd742f7df8c424b0af69a75cd is the first bad commit
>> commit b8afb9113c519a8bd742f7df8c424b0af69a75cd
>> Author: Ville SyrjÃlà <ville.syrjala@xxxxxxxxxxxxxxx>
>> Date: Mon Jun 29 15:25:48 2015 +0300
>>
>> drm/i915: Keep GMCH DPLL VGA mode always disabled
[...]
> @@ -1790,13 +1790,13 @@ static void i9xx_disable_pll(struct intel_crtc
> *crtc)
> /* Make sure the pipe isn't still relying on us */
> assert_pipe_disabled(dev_priv, pipe);
>
> - I915_WRITE(DPLL(pipe), 0);
> + I915_WRITE(DPLL(pipe), DPLL_VGA_MODE_DIS);
> POSTING_READ(DPLL(pipe));
> }
>
>
> That hunk is the only relevant part for your machine. Can you try to revert
> just that manually?
>
> But I'm really surprised that would have any effect since we only used
> to enable "VGA mode" when the DPLL is off. And when the DPLL is off,
> there's nothing on the screen anyway.

Nevertheless, manually reverting just that hunk seems to fix it.

Thanks,
Nick
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