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| author | Mika Kuoppala <mika.kuoppala@linux.intel.com> | 2018-05-08 15:41:54 +0300 |
|---|---|---|
| committer | Mika Kuoppala <mika.kuoppala@linux.intel.com> | 2018-05-11 15:52:21 +0300 |
| commit | ca6acc25250a1dc101c5a541b4f58bcc1dd65de5 (patch) | |
| tree | 5ea00e7451e98bc76727396ac843610d33d1d6b0 /drivers/gpu | |
| parent | 429204f1059909245d8f73b66aa729c6c2807cae (diff) | |
| download | op-kernel-dev-ca6acc25250a1dc101c5a541b4f58bcc1dd65de5.zip op-kernel-dev-ca6acc25250a1dc101c5a541b4f58bcc1dd65de5.tar.gz | |
drm/i915/gtt: Trust the uncached store to flush wcb
Not all architectures guarantee that uncached read will
flush the write combining buffer. So marking it explicitly
is recommended [1].
However we know the architecture we are operating on
and can avoid wmb as the UC store will flush the wcb [2].
Omit the wmb() before invalidate as redudant.
v2: squash combining and removal (Chris)
v3: remove obsolete comments about posting reads (Chris)
References: http://yarchive.net/comp/linux/write_combining.html [1]
References: http://download.intel.com/design/PentiumII/applnots/24442201.pdf [2]
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Matthew Auld <matthew.auld@intel.com>
Signed-off-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20180508124154.14586-1-mika.kuoppala@linux.intel.com
Diffstat (limited to 'drivers/gpu')
| -rw-r--r-- | drivers/gpu/drm/i915/i915_gem_gtt.c | 18 |
1 files changed, 8 insertions, 10 deletions
diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c b/drivers/gpu/drm/i915/i915_gem_gtt.c index c879bfd..6eae9e1 100644 --- a/drivers/gpu/drm/i915/i915_gem_gtt.c +++ b/drivers/gpu/drm/i915/i915_gem_gtt.c @@ -110,7 +110,8 @@ i915_get_ggtt_vma_pages(struct i915_vma *vma); static void gen6_ggtt_invalidate(struct drm_i915_private *dev_priv) { - /* Note that as an uncached mmio write, this should flush the + /* + * Note that as an uncached mmio write, this will flush the * WCB of the writes into the GGTT before it triggers the invalidate. */ I915_WRITE(GFX_FLSH_CNTL_GEN6, GFX_FLSH_CNTL_EN); @@ -2418,11 +2419,9 @@ static void gen8_ggtt_insert_entries(struct i915_address_space *vm, for_each_sgt_dma(addr, sgt_iter, vma->pages) gen8_set_pte(gtt_entries++, pte_encode | addr); - wmb(); - - /* This next bit makes the above posting read even more important. We - * want to flush the TLBs only after we're certain all the PTE updates - * have finished. + /* + * We want to flush the TLBs only after we're certain all the PTE + * updates have finished. */ ggtt->invalidate(vm->i915); } @@ -2460,11 +2459,10 @@ static void gen6_ggtt_insert_entries(struct i915_address_space *vm, dma_addr_t addr; for_each_sgt_dma(addr, iter, vma->pages) iowrite32(vm->pte_encode(addr, level, flags), &entries[i++]); - wmb(); - /* This next bit makes the above posting read even more important. We - * want to flush the TLBs only after we're certain all the PTE updates - * have finished. + /* + * We want to flush the TLBs only after we're certain all the PTE + * updates have finished. */ ggtt->invalidate(vm->i915); } |
