[Mesa-dev] how does mesa/kernel control cache ability of render cache

[Weng, Chuanbo]

Hi all,

               I'm interesting in how mesa/kernel control cache ability of render cache.

               My question is based on SKL platform with console (no-X) environment. We can take kmscube(https://github.com/robclark/kmscube.git)

as an example, it use mesa do rendering and use drm to show result on screen:

               gbm_surface_create to create gbm_surface

               eglCreateWindowSurface to create EGLSurface

               eglMakeCurrent to bind context to EGLSurface

               do rendering using glsl

               eglSwapBuffers

               drmModePageFlip to do page flip



As far as I know, display engine always read memory (not cache) of scanout buffer directly. But mesa use Render Cache Data Port

to render to framebuffer, so the cache path is: Render Cache -> LLC -> Memory. So what does mesa/kernel do to make render cache

coherent with Memory? (I have already seen that cache ability of LLC is set to UC in MOCS of renderbufer. How about render cache?)

Also set render cache to UC? Or just flush render cache before display?







Thanks,

Chuanbo Weng
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