2018-07-02: V3D GPU hang debug, VC4 DSI, VC4 writeback

For V3D, last week I spent mostly building up .CLIF dumping support so that I could talk to the HW team about the GPU hangs I’ve been experiencing. This involved reformatting my dump output, naming some missing (0-filled) fields of the GPU packets I emit, and restructuring the dumper so that I could dump the contents of each BO all at once (whereas before my dumps didn’t really care about BOs and would just dump each memory area as it was found in the worklist).

The final result was a CLIF file I sent to the HW team of a simple transform feedback test that was locking up the GPU. They reported that I was missing a wait packet that was required, beyond what the HW specs said. (I had actually earlier tried emitting the wait, but typoed the condition for enabling it!) With that, I think I’ve cleared up all of the GPU hangs in piglit runs of khr_gles3.

On the VC4 front, the DSI panel enable/disable sequencing patch is in, which should enable other people to successfully build DSI panel drivers for Raspberry Pi. Boris has resubmitted the VC4 writeback (TXP) series now that the core writeback support is in, and there were just a couple of cleanups and it should now be ready to land.