1. 10 Aug, 2013 2 commits
    • Chris Wilson's avatar
      drm/i915: Track when an object is pinned for use by the display engine · cc98b413
      Chris Wilson authored
      The display engine has unique coherency rules such that it requires
      special handling to ensure that all writes to cursors, scanouts and
      sprites are clflushed. This patch introduces the infrastructure to
      simply track when an object is being accessed by the display engine.
      
      v2: Explain the is_pin_display() magic as the sources for obj->pin_count
      and their individual rules is not obvious. (Ville)
      Signed-off-by: default avatarChris Wilson <chris@chris-wilson.co.uk>
      Reviewed-by: default avatarVille Syrjälä <ville.syrjala@linux.intel.com>
      Signed-off-by: default avatarDaniel Vetter <daniel.vetter@ffwll.ch>
      cc98b413
    • Chris Wilson's avatar
      drm/i915: Update rules for reading cache lines through the LLC · c76ce038
      Chris Wilson authored
      The LLC is a fun device. The cache is a distinct functional block within
      the SA that arbitrates access from both the CPU and GPU cores. As such
      all writes to memory land first in the LLC before further action is
      taken. For example, an uncached write from either the CPU or GPU will
      then proceed to memory and evict the cacheline from the LLC. This means that
      a read from the LLC always returns the correct information even if the PTE
      bit in the GPU differs from the PAT bit in the CPU. For the older
      snooping architecture on non-LLC, the fundamental principle still holds
      except that some coordination is required between the CPU and GPU to
      explicitly perform the snooping (which is handled by our request
      tracking).
      
      The upshot of this is that we know that we can issue a read from either
      LLC devices or snoopable memory and trust the contents of the cache -
      i.e. we can forgo a clflush before a read in these circumstances.
      Writing to memory from the CPU is a little more tricky as we have to
      consider that the scanout does not read from the CPU cache at all, but
      from main memory. So we have to currently treat all requests to write to
      uncached memory as having to be flushed to main memory for coherency
      with all consumers.
      Signed-off-by: default avatarChris Wilson <chris@chris-wilson.co.uk>
      Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
      Reviewed-by: default avatarVille Syrjälä <ville.syrjala@linux.intel.com>
      Signed-off-by: default avatarDaniel Vetter <daniel.vetter@ffwll.ch>
      c76ce038
  2. 09 Aug, 2013 11 commits
  3. 08 Aug, 2013 27 commits