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Mon, 04 Feb 2019 08:27:21 -0800 (PST) X-Gm-Message-State: AHQUAuY7G5Lrag8h3/uKzBaAt1uTZmMvrsFfejnDpRF39bIzL4MTMSdS k6sb3UL9Z1x53uKQCv3y9PvzXvAvOgwEYTNN3A== X-Google-Smtp-Source: AHgI3IYtkw6mhtKs/McwJGg3ygf31wr7UsHyWhT/pzLjBzgtl7Yee6yhO4RlLZPY/emx2zyK0xfa53bcomat+NXSVng= X-Received: by 2002:a0c:9e05:: with SMTP id p5mr157588qve.246.1549297640760; Mon, 04 Feb 2019 08:27:20 -0800 (PST) MIME-Version: 1.0 References: <20190203185501.8958-1-anarsoul@gmail.com> <20190203185501.8958-9-anarsoul@gmail.com> <20190204074350.GC16448@ulmo> <20190204082353.GE19087@ulmo> In-Reply-To: <20190204082353.GE19087@ulmo> From: Rob Herring Date: Mon, 4 Feb 2019 10:27:09 -0600 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH RESEND v2 08/12] dt-bindings: add binding for generic eDP panel To: Thierry Reding X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190204_082723_540253_F1CEAC2B X-CRM114-Status: GOOD ( 25.85 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Mark Rutland , devicetree , Archit Taneja , Andrzej Hajda , David Airlie , linux-sunxi , dri-devel , Maxime Ripard , Chen-Yu Tsai , Sean Paul , Laurent Pinchart , Daniel Vetter , arm-linux , Icenowy Zheng Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Mon, Feb 4, 2019 at 2:24 AM Thierry Reding wrote: > > On Mon, Feb 04, 2019 at 12:13:55AM -0800, Vasily Khoruzhick wrote: > > On Sun, Feb 3, 2019 at 11:43 PM Thierry Reding wrote: > > > > > > On Sun, Feb 03, 2019 at 10:54:57AM -0800, Vasily Khoruzhick wrote: > > > > eDP panels usually have EDID EEPROM, so there's no need to define panel > > > > width/height or any modes/timings in dts. But this panel still may have > > > > regulator and/or backlight. > > > > > > > > Signed-off-by: Vasily Khoruzhick > > > > --- > > > > .../devicetree/bindings/display/panel/panel-edp.txt | 7 +++++++ > > > > 1 file changed, 7 insertions(+) > > > > create mode 100644 Documentation/devicetree/bindings/display/panel/panel-edp.txt > > > > > > Please don't try to make panels look more generic than they really are. > > > You're going to have to provide a compatible string for your device that > > > is more specific than "panel-edp". You claim that you don't need any > > > extra information that is panel specific, but you don't know that now. > > > We have in the past thought that we didn't need things like prepare > > > delay, but then we ran into situations where we did need them. > > > > > > Just do what everybody else does. Provide a specific compatible string > > > and match on that in the panel-simple driver. Even if you can read all > > > the video timings from an EDID EEPROM, you can still provide a mode in > > > the panel descriptor to serve as a fallback if for example the EEPROM > > > is faulty on some device. > > > > Pinebook used several 768p panels that have slightly different timings > > and recent batch uses 1080p panel. > > > > What panel descriptor should I use as fallback? > > You don't use panel descriptors as fallback. The simple-panel driver > will bind to a panel device and use the corresponding descriptor. If > your device tree contains the correct information, the descriptor is > correct for the panel you have. > > In other words you need to ensure that you have the correct panel in > device tree for the board that you're using. This is exactly the same > thing as for other devices. > > One way to to this is to have separate device trees for each variant > of the board that you want to support. Another variant may be to have > a common device tree and then have some early firmware update the DTB > with the correct panel information. That can be a pain to manage especially if panels are swapped run to run with 2nd sources. I think it is perfectly fine to have a generic-ish fallback as long as it is just that, a fallback. If the panel has quirks, then you'd better make sure the firmware is stuffing in the right compatibles or that you can update the firmware. Rob _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel