driving 1200x1920 screen

[vdl]

I'm in a bit of a pickle. I got a MIPI DSI screen with 1200x1920 resolution. It turns out for SMT32MP25x max vertical supported resolution is 1536. But datasheet says this. 

 

Some over-target non-guaranteed use cases are possible, but with specific constraints:
• Drive simultaneously three panels, using the three interfaces (parallel, LVDS, DSI), with
a same content.
• Drive simultaneously two parallel LVDS panels, using each one link, with a reduced
resolution and a same content.
• Drive a 4 k panel via the DSI, with a limited features and performances: one layer,
no resize, no rotation, 30 fps, and non-standardized blanking sizes.

 

How do i specify those params in dts or/and linux panel driver?

 

I tried setting 30Hz on panel, but that did not help - linux drm fails with "vblank wait timed out"

This fails - 1200x1920@30Hz

.clock = 80288,

.hdisplay = 1200,

.hsync_start = 1200 + 32,

.hsync_end = 1200 + 32 + 14,

.htotal = 1200 + 32 + 14 + 26,

.vdisplay = 1920,

.vsync_start = 1920 + 144,

.vsync_end = 1920 + 144 + 8,

.vtotal = 1920 + 144 + 8 + 32,

 

But this works 1920x1200@58.63Hz ( works as in does not throw kernel error - display obviously does not work as it expects different resolution )

.clock = 156900,

.hdisplay = 1920,

.hsync_start = 1920 + 144,

.hsync_end = 1920 + 144 + 8,

.htotal = 1920 + 144 + 8 + 32,

.vdisplay = 1200,

.vsync_start = 1200 + 32,

.vsync_end = 1200 + 32 + 14,

.vtotal = 1200 + 32 + 14 + 26,

 

[MM..1]

Are you sure that register vtotal can write 1920 + 144 + 8 + 32 = >2048 value ?

I mean only htotal is in range for this hw.

[vdl]

registers for vsync/hsync are 12bit wide so it should be enough. also documentation hints that 4k resolution is supported in special case which is more than i need

[vdl]

problem fixed by reducing v front porch from 144 to 44 ( did not tried other values ) 

 

weird but sum of vtotal is now below 2048 - maybe thats whats caused vblank timeout to happen before