On Mon, Feb 4, 2019 at 8:39 AM Rob Herring <robh+dt@xxxxxxxxxx> wrote: > > On Mon, Feb 4, 2019 at 10:11 AM Vasily Khoruzhick <anarsoul@xxxxxxxxx> wrote: > > > > On Mon, Feb 4, 2019 at 12:24 AM Thierry Reding <thierry.reding@xxxxxxxxx> 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
