drm/i915: Prefer memset64() when filling the iomap

As the ringbuffer may exist inside stolen memory, our access to it may
be via the GTT iomap. This implies we may only have WC access for which
the conventional memset() substitution of rep stos performs very badly,
so switch to the rep mov[dq] variants when available.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@intel.com>
Cc: Matthew Auld <matthew.auld@intel.com>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180319123528.28249-1-chris@chris-wilson.co.uk

diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
index 72d6167..04d9d9a 100644 (file)
--- a/drivers/gpu/drm/i915/intel_ringbuffer.c
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
@@ -1693,17 +1693,18 @@ u32 *intel_ring_begin(struct i915_request *rq, unsigned int num_dwords)
                need_wrap &= ~1;
                GEM_BUG_ON(need_wrap > ring->space);
                GEM_BUG_ON(ring->emit + need_wrap > ring->size);
+               GEM_BUG_ON(!IS_ALIGNED(need_wrap, sizeof(u64)));
 
                /* Fill the tail with MI_NOOP */
-               memset(ring->vaddr + ring->emit, 0, need_wrap);
-               ring->emit = 0;
+               memset64(ring->vaddr + ring->emit, 0, need_wrap / sizeof(u64));
                ring->space -= need_wrap;
+               ring->emit = 0;
        }
 
        GEM_BUG_ON(ring->emit > ring->size - bytes);
        GEM_BUG_ON(ring->space < bytes);
        cs = ring->vaddr + ring->emit;
-       GEM_DEBUG_EXEC(memset(cs, POISON_INUSE, bytes));
+       GEM_DEBUG_EXEC(memset32(cs, POISON_INUSE, bytes / sizeof(*cs)));
        ring->emit += bytes;
        ring->space -= bytes;