drm/v3d: Skip CSD when it has zeroed workgroups

drm/v3d: Skip CSD when it has zeroed workgroups

A compute shader dispatch encodes its workgroup counts in the CFG0..CFG2
registers. Kicking off a dispatch with a zero count in any of the three
dimensions is invalid. First, the hardware will process 0 as 65536,
while the user-space driver exposes a maximum of 65535. Over that, a
submission with a zeroed workgroup dimension should be a no-op.

These zeroed counts can reach the dispatch path through an indirect CSD
job, whose workgroup counts are only known once the indirect buffer is
read and may legitimately be zero, but such scenario should only result in
a no-op.

Overwrite the indirect CSD job workgroup counts with the indirect BO
ones, even if they are zeroed, and don't submit the job to the hardware
when any of the workgroup counts is zero, so the job completes immediately
instead of running the shader.

Cc: stable@vger.kernel.org
Fixes: d223f98f0209 ("drm/v3d: Add support for compute shader dispatch.")
Suggested-by: Jose Maria Casanova Crespo <jmcasanova@igalia.com>
Reviewed-by: Iago Toral Quiroga <itoral@igalia.com>
Link: https://patch.msgid.link/20260602-v3d-fix-indirect-csd-v4-2-654309e32bc0@igalia.com
Signed-off-by: Maíra Canal <mcanal@igalia.com>