Hi,
If you submit a lot of graphics and DMA IBs interleaved, the graphics CS checker sometimes fails with this message:
[ 3846.435661] Forbidden register 0x0014 in cs at 9 [ 3846.435664] [drm:radeon_cs_ib_chunk] *ERROR* Invalid command stream !
This error is only used for type-0 packets, but we don't use these packets on R700 at all. Somehow, the graphics CS checker received either the DMA IB or random garbage. My guess is there is memory corruption happening during IB uploading and/or IB checking in the kernel. Also, if you are unlucky, the GPU hangs instead.
The CS thread offloading was disabled in Mesa, so the user space was single-threaded.
There are 2 ways to fix this: - disable async DMA in Mesa - call usleep(1) after the RADEON_CS ioctl returns
This is just a heads-up. In the worst case, we can disable async DMA for R700 in Mesa.
Marek