[PATCH 0/1][SRU][Focal] Intermittent display blackouts on event

[You-Sheng Yang]

This affects also:

Groovy: 802cf455226c (clean apply)
Eoan: 128a27cef42a (clean apply)
OEM-OSP1-B: b9fc3db3ffa2 (need backport)

On 2020-04-29 10:55, AceLan Kao wrote:
> BugLink: https://bugs.launchpad.net/bugs/1875254
> 
> [Impact]
> When audio device enters runpm D3(idle for 7 seconds) and then wakes it up
> to make a sound, it flicks the screen.
> This behavior could be observed while plug/remove AC cable or USB disk,
> or open a terminal and press backsapce key.
> 
> [Fix]
> This issue could be fixed by this commit, it fixes the flicker during
> boot-time, but it also fixes the flicker during rumtime wakeup.
> 1ee48a61aa57 drm/i915: Limit audio CDCLK>=2*BCLK constraint back to GLK only
> 
> Audio drivers communicate with i915 over HDA bus multiple times during
> system boot-up and each of these transactions result in matching
> get_power/put_power calls to i915, and depending on the platform,
> a modeset change causing visible flicker.
> 
> GLK is the only platform with minimum CDCLK significantly lower
> than BCLK, and thus for GLK setting a higher CDCLK is mandatory.
> 
> For other platforms, minimum CDCLK is close but below 2*BCLK
> (e.g. on ICL, CDCLK=176.4kHz with BCLK=96kHz). Spec-wise the constraint
> should be set, but in practise no communication errors have been
> reported and the downside if set is the flicker observed at boot-time.
> 
> [Test]
> Verified on Dell XPS 13 9300
> 
> [Regression Potential]
> Low, it fixes below commit which contains in ubuntu kernel and should have
> been applied on ubuntu kernel, too.
> Fixes: f6ec9483091f ("drm/i915: extend audio CDCLK>=2*BCLK constraint to more platforms")
> 
> Kai Vehmanen (1):
>   drm/i915: Limit audio CDCLK>=2*BCLK constraint back to GLK only
> 
>  drivers/gpu/drm/i915/display/intel_audio.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 

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