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[209.85.128.51]) by smtp.gmail.com with ESMTPSA id d3-20020a056402000300b00553772c2968sm347735edu.82.2023.12.20.14.43.18 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 20 Dec 2023 14:43:18 -0800 (PST) Received: by mail-wm1-f51.google.com with SMTP id 5b1f17b1804b1-40d3b2c8517so5025e9.1 for ; Wed, 20 Dec 2023 14:43:18 -0800 (PST) X-Received: by 2002:a05:600c:1c27:b0:40c:256f:756b with SMTP id j39-20020a05600c1c2700b0040c256f756bmr50610wms.2.1703112197939; Wed, 20 Dec 2023 14:43:17 -0800 (PST) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 References: <20231220221418.2610185-1-hsinyi@chromium.org> In-Reply-To: <20231220221418.2610185-1-hsinyi@chromium.org> From: Doug Anderson Date: Wed, 20 Dec 2023 14:43:02 -0800 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH] drm/panel-edp: use put_sync in unprepare To: Hsin-Yi Wang Cc: Neil Armstrong , Jessica Zhang , Sam Ravnborg , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Daniel Vetter , Linus Walleij , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Hi, On Wed, Dec 20, 2023 at 2:14=E2=80=AFPM Hsin-Yi Wang = wrote: > > Some edp panel requires T10 (Delay from end of valid video data transmitt= ed > by the Source device to power-off) less than 500ms. Using autosuspend wit= h > delay set as 1000 violates this requirement. > > Use put_sync_suspend in unprepare to meet the spec. For other cases (such > as getting EDID), it still uses autosuspend. > > Suggested-by: Douglas Anderson > Fixes: 5f04e7ce392d ("drm/panel-edp: Split eDP panels out of panel-simple= ") Probably instead: Fixes: 3235b0f20a0a ("drm/panel: panel-simple: Use runtime pm to avoid excessive unprepare / prepare") ...you could send a new version or I could just fix it up when I apply it. > Signed-off-by: Hsin-Yi Wang > --- > drivers/gpu/drm/panel/panel-edp.c | 3 +-- > 1 file changed, 1 insertion(+), 2 deletions(-) Yeah, it's really unfortunate but I think we have to do this. It will add big delays any time we need to turn the panel off and quickly back on again, but I don't think we can reliably meet T10 without it. Even turning down the autosuspend delay won't really help since someone could do something like read the EDID while the delay was happening to reset the delay. At least we can still use "autosuspend" to avoid powering off between reading the EDID and powering up the panel since the EDID grabs runtime_pm itself and still uses autosuspend. I don't remember this particular problem before and nobody has yelled about it in the past. ...and the requirement seems crazy, but it certainly is in the spec sheets so we should be good citizens and honor it. On the plus side, this means that we will always fully power cycle the panel whenever we turn video off and that means that if any other panels out there have weird issues like "samsung-atna33xc20" this will also fix them since this is the same fix I had to do in that driver. In any case: Reviewed-by: Douglas Anderson I'm about to go on vacation, so I won't apply this until January. Other drm-misc maintainers are free to apply sooner than that if they're comfortable with it.