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a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=nHIv2ayL4rpJq73Zv/i3JenXqZ3Mmi6DM/rkqyVhHQY=; b=RZJT01BhTlAlbYTbuvGBSYqb0sia+2qgORqeNdTY1E58zABwdAW02Smmvo+qn9/xKF MDrC00GlIRINttnP0OWgPn9Iyh7K8KL0MkNY8x+SfW9p/7hRKD1CU43rMzrnzQNF07yn 4NPmSHDY8uuqDXqmvLm68DZvMnVE/cTAb+y02xDSMP823gm2jFFJTZDLnxtmsQWFVA34 JOZgFrP0irDnHI1oqk7TI1Oc+dU6PYyvqjHvHlk3/g3/m04U7FodqmFpAWtOz1DHJq2x KoWiIV5NJObqm4ycNCBqjQzXRLaqIhMMrx5rNe8vJ5E4Pat2/2kW2B8trZVvKAbx2VsT u6Ig== X-Gm-Message-State: AHQUAuZj77tB/1jiCOBQK5qp6NnQC8tn1ydN1POJnvj3+tPfOQzsrZfT xU7RoTclY0g3FyIl9D22EQCIxuKbuuoy7fHs8Fo= X-Google-Smtp-Source: AHgI3IYpZIQITKXmFr6eiK47r/3RWnbfTK5vm4QNaweeMEsWzF55YA/M+EBrGmoepIPXYGgQOFDOTK0m9mk/P3rxAVY= X-Received: by 2002:aca:f044:: with SMTP id o65mr158146oih.145.1549299794847; Mon, 04 Feb 2019 09:03:14 -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: From: Vasily Khoruzhick Date: Mon, 4 Feb 2019 09:02:48 -0800 Message-ID: Subject: Re: [linux-sunxi] Re: [PATCH RESEND v2 08/12] dt-bindings: add binding for generic eDP panel To: Rob Herring X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190204_090316_134186_95123111 X-CRM114-Status: GOOD ( 23.40 ) 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 , Thierry Reding , 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 8:39 AM Rob Herring wrote: > > On Mon, Feb 4, 2019 at 10:11 AM Vasily Khoruzhick wrote: > > > > On Mon, Feb 4, 2019 at 12:24 AM Thierry Reding wrote: > > > > > > > > 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 defeats the purpose of using eDP panels. Panel can identify > > itself and report what timings it supports. > > If you are confident that this works for all panels, then the firmware > can identify the right panel and update the DTB with the correct > information. If this doesn't work in the firmware, then it is not > going to work in the kernel either and you are SOL without specific > panel information in the DT. "firmware" is u-boot and on this platform it sits on the same physical media as OS (it's either microsd or eMMC). I guess u-boot can fill in timings for kernel, but I don't see much point in it. If u-boot can't read EDID then same is true for kernel. > > If we use separate DTBs then users will have to figure out what panel > > is installed in their hardware and use appropriate software image - > > that's something I'd like to avoid. > > I think Thierry meant either way this is a firmware problem. If you > have a SKU per device and panel type, then the firmware just picks a > dtb among a set. Unfortunately it's one SKU per multiple panels. > Rob _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel