On Wed, May 29, 2019 at 08:23:17AM +0200, Linus Walleij wrote:
On Wed, May 29, 2019 at 3:17 AM Brian Masney masneyb@onstation.org wrote:
It's in low speed mode but its usable.
How low speed is that?
I don't have a number but my test with 4.17 is to run 'cat /etc/passwd > /dev/tty1' over a serial cable. The first 2-3 calls will fill up the screen and the file contents appear to show up on the screen immediately to the human eye. The next time that I run it requires scrolling the entire console and there is a small fraction of a second where I see the entire framebuffer contents scroll up. I don't have a graphics background, but I believe that this is the tearing effect that I'm seeing based on what I've read. I believe that disp-te-gpios can be used to mitigate this tearing effect. I have a few questions about this later once we get the basic display working.
I assume that it's related to the vblank events not working properly?
They are only waiting for 50 ms before timing out, I raised it to 100ms in the -next kernel. I'm still suspicious about this even though I think you said this was not the problem.
For a command mode panel in LP mode it will nevertheless be more than 100ms for sure, the update is visible to the naked eye.
Raise it to 10000 ms or something and see what happens. drivers/gpu/drm/drm_atomic_helper.c: msecs_to_jiffies(50)
I previously raised those timeouts as high as 5 seconds and it still has the same issue. Writing to /dev/tty1 can take anywhere between a few seconds to 30 seconds or more.
Brian