[Letux-kernel] LX16 SPI Display

[H. Nikolaus Schaller]

Hi Paul,

> Am 14.01.2025 um 14:21 schrieb H. Nikolaus Schaller <hns at goldelico.com>:
> 
> So this may be an issue or the issue to play with polarity/phase:
> 
> (Bootlin Elixier seems to have hickups and the last update is 6.13-rc3).
> 
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/devicetree/bindings/spi/spi-controller.yaml?h=v6.13-rc7#n120

Ok, I played with spi-cpol and spi-cpha but it seems to have no effect which is a little unexpected.

With 50MHz I have an image but colors are disturbed. Ah, now I finally see what the problem with cat /dev/urandom >/dev/fb0 is: you won't see such color errors... This is where fbi would be nice.

Ah, my memory is becoming better... We have a nice tool in Letux/root/fbtest

https://git.goldelico.com/?p=letux-kernel.git;a=blob;f=Letux/root/fbtest;h=8dd257b8b5cf6cd40e9eb2058e26f4aacc243c66;hb=HEAD

It was developed by notaz at openpandora.org one decade ago to test the Pyra TILER rotation of the framebuffer. It just may need a little polishing to be compiled correctly on MIPS (there is an implicit assumption for ARM). But attempting to run leads to:

root at letux:~# ./fbpng 1280x720_board.png
1280x720_board.png: 1280x720 @ 24bpp
ioctl(FBIOPUT_VSCREENINFO): Invalid argument
Bus error
root at letux:~# 

The Bus error is because there is no exit in error case. But the ioctl is still defined.

Regarding spi-cpol and spi-cpha: do you know if this is generic or if these flags have to be handled by the spi-controller driver?

BR,
Nikolaus