• Chris Wilson's avatar
    drm/i915: Enable render context support for gen4 (Broadwater to Cantiga) · 9ce9bdb0
    Chris Wilson authored
    Broadwater and the rest of gen4  do support being able to saving and
    reloading context specific registers between contexts, providing isolation
    of the basic GPU state (as programmable by userspace). This allows
    userspace to assume that the GPU retains their state from one batch to the
    next, minimising the amount of state it needs to reload and manually save
    across batches.
    
    v2: CONSTANT_BUFFER woes
    
    Running through piglit turned up an interesting issue, a GPU hang inside
    the context load. The context image includes the CONSTANT_BUFFER command
    that loads an address into a on-gpu buffer, and the context load was
    executing that immediately. However, since it was reading from the GTT
    there is no guarantee that the GTT retains the same configuration as
    when the context was saved, resulting in stray reads and a GPU hang.
    
    Having tried issuing a CONSTANT_BUFFER (to disable the command) from the
    ring before saving the context to no avail, we...
    9ce9bdb0
intel_ringbuffer.c 60.6 KB