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drm/i915/vlv: Update Wait for FIFO and wait for 20 free entries. v3

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On VLV, FIFO will be shared by both SW and HW. So, we read the
free entries through register and update dev_priv variable
and wait for only 20 entries to be free

From Deepak's follow-up mail explaining why vlv is special:

"On SB, Out of 64 FIFO Entries, 20 Entries will be used by HW and
remaining 44 will be used by the SW,. I think due to this reason, we
have a threshold of 20 Entries."

"On VLV, HW and SW can access all 64 fifo entries, I don't think
having a threshold of 20 Entries is mandatory on VLV. Also, since both
SW and HW can access all 64 Entries. I think on VLV, we need to update
the fifo_count before waiting for the FIFO."

v2: Apply mask when we read the number of free FIFO entries (Ville).

v3: Mask applied after reading the register (Deepak).

Signed-off-by: Deepak S <deepak.s@intel.com>
[danvet: Add further explanation from Deepak to commit message.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
This commit is contained in:
Deepak S 2013-11-29 15:56:30 +05:30 committed by Daniel Vetter
parent 1f1c2e2468
commit 5135d64b7f
1 changed files with 7 additions and 0 deletions
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7
drivers/gpu/drm/i915/intel_uncore.c
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@ -150,6 +150,13 @@ static int __gen6_gt_wait_for_fifo(struct drm_i915_private *dev_priv)
{
int ret = 0;
/* On VLV, FIFO will be shared by both SW and HW.
* So, we need to read the FREE_ENTRIES everytime */
if (IS_VALLEYVIEW(dev_priv->dev))
dev_priv->uncore.fifo_count =
__raw_i915_read32(dev_priv, GTFIFOCTL) &
GT_FIFO_FREE_ENTRIES_MASK;
if (dev_priv->uncore.fifo_count < GT_FIFO_NUM_RESERVED_ENTRIES) {
int loop = 500;
u32 fifo = __raw_i915_read32(dev_priv, GTFIFOCTL) & GT_FIFO_FREE_ENTRIES_MASK;