On Thu, Feb 13, 2020 at 08:11:10PM +0200, Andrey Lebedev wrote:
On Thu, Feb 13, 2020 at 10:24:33AM +0100, Maxime Ripard wrote:
do you have a board when you have been able to test it?
Yes, I have the hardware (Cubieboard 2) at hand, but I cannot change the any physical connections on it. FWIW, it is https://openvario.org, the device we are (painfully) trying to upgrade from old kernel-3.4 with proprietary mali drivers to contemporary software.
What painpoints do you have?
So, even though proprietary mali drivers worked well for us, they seem to hold us back to old kernel-3.4, and it started to get harder to avoid various compatibility issues with newer software. Since there seemed to be a good progress with OSS lima driver lately, we decided to try to replace mali with lima. And that naturally pulled to switch to DRM/KMS.
You can use the proprietary mali drivers with mainline too, but yeah it's in maintainance mode these days and you should go for lima if you're (re)starting from scratch.
The first painpoint is this LVDS support problem: after a week of trial and error, I discovered that support was simply not there. But it seemed that not that much was actually missing and after couple of evenings deep into debugging, here we are.
Another one is the screen rotation: the device is installed into the glider' instrument panel, and some pilots prefer it in portrait orientation. Under old mali setup, all that (seemingly) was required was setting "fbcon=rotate:n" boot arg, and both linux console and graphical app (https://xcsoar.org/) rotated "automagically". With new DRM/KMS setup, only console is rotated, all graphical apps seem to see the screen in its "natural" landscape orientation. Do you know if there is any way to leverage DMS/KMS infrastructure to make screen appear rotated for userspace apps (writing to /sys/class/graphics/fb0/rotate didn't work)? There's of course a plan B to teach the app to rotate its output, but that leads to problem number 3.
There's a rotation property that can be set by whatever you're using on top of KMS, DRM_MODE_ROTATE_*, but I'm not sure the driver supports it at the moment.
And the 3rd outstanding problem is that app doesn't really work under lima module and lima mesa driver. It starts, but renders a black window. I haven't dug deeply into this yet, but it is possible that some opengl API isn't supported in OSS drivers yet (even though app only renders 2d graphics).
I have no idea on this one though, sorry :/
Maxime