Re: [PATCH 0/3] drm: tinydrm driver for adafruit PiTFT 3.5" touchscreen

From: Noralf TrÃnnes
Date: Wed Oct 31 2018 - 12:28:05 EST

Den 25.10.2018 18.29, skrev Eric Anholt:
Eric Anholt <eric@xxxxxxxxxx> writes:

I was going to start working on making the vc4 driver work with
tinydrm panels, but it turned out tinydrm didn't have the panel I had
previously bought. So, last night I ported the fbtft staging
driver over to DRM.

It seems to work (with DT at --
fbdev works great including rotated, and so does modetest. However,
when X11 comes up at 16bpp, I get:

If I have tinydrm set a preferred bpp of 24, X looks great. Noralf,
any ideas?
Also, with these patches and the format modifier patch I just sent, mesa
with vc4 is now working with this driver on this branch:

Now I wonder how we can improve performance of the SPI updates.

I just remembered that tinydrm does a full flush on page flips. And if
the dirtyfb ioctl is also used you end up with two flushes. This could
explain bad performance. I have been waiting for the dirtyfb through
atomic work to come to fruition, but nothing merged yet. That would give
dirty tracking on page flips.