2018-03-12: VHCI, V4L2, VC4 perfmon

This week I wrote a little patch series to get VCHI probing on upstream Raspberry Pi. As we’re building a more normal media stack for the platform, I want to get this upstreamed, and VCHI is at the root of the firmware services for media.

Next step for VCHI upstreaming will be to extract Dave Stevenson’s new VCSM driver and upstream it, which as I understand it lets you do media decode stuff without gpu_mem= settings in the firmware – the firmware will now request memory from Linux, instead of needing a fixed carveout. That driver will also be part of the dma-buf plan for the new v4l2 mem2mem driver he’s been working.

Dave Stevenson has managed to produce a V4L2 mem2mem driver doing video decode/encode. He says it’s still got some bugs, but things look really promising.

In VC4 display, Stefan Schake submitted patches for fixing display plane alpha blending in the DRM hwcomposer for Android, and I’ve merged them to drm-misc-next.

I also rebased my out-of-tree DPI patch, fixed the regression from last year, and submitted patches upstream and downstream (including a downstream overlay). Hopefully this can help other people attach panels to Raspberry Pi.

On the 3D side, I’ve pushed the YUV-import accelerated blit code. We should now be able to display dma-bufs fast in Kodi, whether you’ve got KMS planes or the fallback GL composition.

Also, now that the kernel side has made it to drm-next, I’ve pushed Boris’s patches for vc4 perfmon into Mesa. Now you can use commands like:

apitrace replay application.trace

to examine behavior of your GL applications on the HW. Note that each doing –pdraw level tracing (instead of –pframes) means that each draw call will flush the scene, which is incredibly expensive in terms of memory bandwidth.