On 28.08.2018 15:45, Linus Walleij wrote: > On Mon, Aug 27, 2018 at 1:53 PM Andrzej Hajda <a.hajda@xxxxxxxxxxx> wrote: > >> On 24.08.2018 14:23, Linus Walleij wrote: >>> This adds bindings for a virtual display to be used with displays >>> inside entirely virtual environments which do not emulate things >>> like monitors but just need timing information to be supplied to >>> its display controller. >>> >>> This is inspired by earlier work by Liviu Dudau. >> If this is pure virtual then it should be connected to other pure >> virtual components. > OK it's a bit of half-half but outside of my grasp, I am just trying > to support legacy systems. > > The device tree is there: > arch/arm64/boot/dts/arm/rtsm_ve-aemv8a.dts > arch/arm64/boot/dts/arm/rtsm_ve-motherboard.dtsi > > The latter contains the CLCD which is the display driver. > > In RTSM, which is an ARM product I do not develop and > cannot make changes to, there is an emulated CLCD. So > that part appear as if it was real hardware. Like in QEMU. > > But the display does not have any emulation. The raw > output from the CLCD is latched out to the screen. > > I do not know exactly know how the RTSM emulator > actually works, but I suspect that the little graphic window > on the screeen adapts to what gets written into the > CLCD control registers, so anything goes, more or less. > > To satisfy the CLCD with some timings and resolution, > this bridge gives it that, from the device tree, in a way > that clearly conveys that "this is not a real thing". > > The old code uses DPI. This is not DPI, not even close > to it. It worked simply because all the DPI really does is > what this patch does: provide timings. > > By contrast on QEMU I have patches the emulator to > properly represent the I2C DDC link and provide EDID > so that is all fine. > > I cannot patch RTSM to emulate I2C and DDC. It's not > open source. But the device tree in the kernel supports > this "machine" and so, I have to maintain it when modernizng > the fbdev driver to a DRM driver. > > I'm sorry RTSM is half/half. Not my fault. I can't fix... I do not know the platform, so I I have dug little bit, but I wan't call it thorough research. Just please be kind if I wrote sth stupid. What I have found: 1. DTS shows CLCD is pl111. 2. pl111 documentation says it's output interface supports STN and TFT up to 24-bit bus. I do not know STN, but TFT seems to be compatible with DPI. If it is correct, dpi panel seems to be OK. And I think it is less important how the emulator works, more important is that it should emulate pl111, including it's output interfaces. Regards Andrzej > >> And one more thing, you are defining virtual panel but you are using >> drm_bridge framework, why not drm_panel? > This was discussed before in the previous patch set: > https://lists.freedesktop.org/archives/dri-devel/2018-July/183516.html > > Essentially, it's because the display driver is just connected > to "something" not a panel and a bridge is likely the best I > can come up with - a bridge over to a virtual display. > > A patch to add "VGA", "SGA" and "XGA" to the simple panels > was NACKed (sort of, politely): > https://lists.freedesktop.org/archives/dri-devel/2018-July/183698.html > > Also it was noted that it would be nice to have something that > would make it easy to change resolutions on these virtual > display things. Voila. > > Yours, > Linus Walleij > > _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
