On Wed, Aug 29, 2018 at 12:23:18PM +0200, Andrzej Hajda wrote: > On 29.08.2018 12:01, Liviu Dudau wrote: > > On Wed, Aug 29, 2018 at 11:58:20AM +0200, Andrzej Hajda wrote: > >> 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. > > Yeah, unfortunately that ship has sailed a long time ago. The emulator > > people thought emulating the register interface is good enough and took > > liberties on how the behaviour was "emulated". End result: output > > interfaces are not the same. > > So what is wrong/missing with dpi panel? Linus explained in the links he quoted below. I'll let him add more if he has additional information. Best regards, Liviu > > Regards > Andrzej > > > > > Best regards, > > Liviu > > > >> 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 > >>> > >>> > -- ==================== | I would like to | | fix the world, | | but they're not | | giving me the | \ source code! / --------------- ¯\_(ツ)_/¯ _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
