The read back of the available FIFO entries is vital for system
stability, but extremely costly. However, we only need a guide so as to
avoid eating into the reserved entries and since we are the only
consumer we can cache the read of the count from the last write.
Signed-off-by: Chris Wilson <ch...@chris-wilson.co.uk>
Reviewed-by: Ben Widawsky <b...@bwidawsk.net>
---
drivers/gpu/drm/i915/i915_drv.c | 15 ++++++++++-----
drivers/gpu/drm/i915/i915_drv.h | 1 +
drivers/gpu/drm/i915/i915_reg.h | 1 +
3 files changed, 12 insertions(+), 5 deletions(-)
diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
index c416c1d..5d0d28c 100644
--- a/drivers/gpu/drm/i915/i915_drv.c
+++ b/drivers/gpu/drm/i915/i915_drv.c
@@ -287,12 +287,17 @@ void __gen6_gt_force_wake_put(struct drm_i915_private
*dev_priv)
void __gen6_gt_wait_for_fifo(struct drm_i915_private *dev_priv)
{
- int loop = 500;
- u32 fifo = I915_READ_NOTRACE(GT_FIFO_FREE_ENTRIES);
- while (fifo < 20 && loop--) {
- udelay(10);
- fifo = I915_READ_NOTRACE(GT_FIFO_FREE_ENTRIES);
+ if (dev_priv->gt_fifo_count < GT_FIFO_NUM_RESERVED_ENTRIES ) {
+ int loop = 500;
+ u32 fifo = I915_READ_NOTRACE(GT_FIFO_FREE_ENTRIES);
+ while (fifo <= GT_FIFO_NUM_RESERVED_ENTRIES && loop--) {
+ udelay(10);
+ fifo = I915_READ_NOTRACE(GT_FIFO_FREE_ENTRIES);
+ }
+ WARN_ON(loop < 0 && fifo <= GT_FIFO_NUM_RESERVED_ENTRIES);
+ dev_priv->gt_fifo_count = fifo;
}
+ dev_priv->gt_fifo_count--;
}
static int i915_drm_freeze(struct drm_device *dev)
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 759045a..9b22f11 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -268,6 +268,7 @@ typedef struct drm_i915_private {
int relative_constants_mode;
void __iomem *regs;
+ u32 gt_fifo_count;
struct intel_gmbus {
struct i2c_adapter adapter;
diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index f39ac3a..e6bfe94 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -3329,6 +3329,7 @@
#define FORCEWAKE_ACK 0x130090
#define GT_FIFO_FREE_ENTRIES 0x120008
+#define GT_FIFO_NUM_RESERVED_ENTRIES 20
#define GEN6_RPNSWREQ 0xA008
#define GEN6_TURBO_DISABLE (1<<31)
--
1.7.4.1
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