[Intel-gfx] [PATCH] drm/i915/dsi: Silence atomic update failure with DSI panel

[Martin Peres]

On 06/09/17 13:09, Mika Kahola wrote:
> On Tue, 2017-09-05 at 18:11 +0200, Daniel Vetter wrote:
>> On Tue, Sep 05, 2017 at 04:35:04PM +0300, Mika Kahola wrote:
>>>
>>> It appears that we cannot trust scanline counters when MIPI/DSI
>>> display is
>>> connected. In CI system this appears as flickering errors that
>>> randomly
>>> appear in test cases. To avoid this flickering, let's just silence
>>> atomic
>>> update failure in case with DSI panel.
>>>
>>> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=102403
>>> Signed-off-by: Mika Kahola <mika.kahola at intel.com>
>> This just changes a loud atomic failure to a silent atomic failure.
>> What
>> we instead need to do is actually fix the bug, not hide it.
>>
> BSpec has a notion that (PIPE_SCANLINE) that is "Not supported with
> MIPI DSI."
> 
> That's why I thought it might be ok to silence the error as the
> computation that we try to accomplish wouldn't work anyway. Maybe this
> way we could remove DSI from being blackllisted.

I agree. If the HW can't do it, so what can we do here?

As long as this is well documented and the userspace knows about this 
issue (if anything relies on this feature), then what else can we do?

With the relevant BSpec quotes added above the changes, I can give my:
Acked-by: Martin Peres <martin.peres at linux.intel.com>

I would however like to know if this breaks any feature the userspace 
relies on.

Martin