[Intel-gfx] [PATCH] drm/i915: add missing "break"

[Paulo Zanoni]

Hi

2011/9/23 Keith Packard <keithp at keithp.com>:
> On Fri, 23 Sep 2011 08:13:15 +0530, Jesse Barnes <jbarnes at virtuousgeek.org> wrote:
>> What I don't understand about the refclk code is that we should be able
>> to leave everything enabled and just select the right clock source in
>> the DPLL_SEL bits.  But that doesn't seem to help the wavy VGA bug,
>> since in that case I think we're explicitly choosing the non-SSC clock
>> and we still get waviness.
>
> We don't have any hardware anywhere which exhibits this problem, do we?
> Getting hold of some would let us poke at it.

My personal laptop reproduces the "wavy output" problem.

If you look at the patch posted on comment #20 of bug #38750 [0],
you'll see that it checks on the video bios for a field called
"display_clock_mode" and then uses this field in the following code:
+		if (dev_priv->display_clock_mode)
+			temp |= DREF_NONSPREAD_CK505_ENABLE;
+		else
+			temp |= DREF_NONSPREAD_SOURCE_ENABLE;

This is what fixes the wavy output problem: setting
DREF_NONSPREAD_CK505_ENABLE instead of the other bits.

And for Keith's patch:

Tested-By: Paulo Zanoni <paulo.r.zanoni at intel.com>

[0]: https://bugs.freedesktop.org/attachment.cgi?id=49888

-- 
Paulo Zanoni