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[220.135.95.34]) by smtp.gmail.com with ESMTPSA id s145sm14409698pgs.57.2020.04.28.19.55.29 for (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 28 Apr 2020 19:55:30 -0700 (PDT) From: AceLan Kao To: kernel-team@lists.ubuntu.com Subject: [PATCH 0/1][SRU][Focal] Intermittent display blackouts on event Date: Wed, 29 Apr 2020 10:55:27 +0800 Message-Id: <20200429025528.236678-1-acelan.kao@canonical.com> X-Mailer: git-send-email 2.25.1 MIME-Version: 1.0 X-BeenThere: kernel-team@lists.ubuntu.com X-Mailman-Version: 2.1.20 Precedence: list List-Id: Kernel team discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: kernel-team-bounces@lists.ubuntu.com Sender: "kernel-team" 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(-) Acked-by: Stefan Bader