Re: [PATCH 08/13] drm/i915: Implement MI decode for gen8

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Tue, Apr 29, 2014 at 02:52:35PM -0700, Ben Widawsky wrote:
> From: Ben Widawsky <benjamin.widawsky@linux.intel.com>
> 
> This is needed to implement ipehr_is_semaphore_wait
> 
> Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
> ---
>  drivers/gpu/drm/i915/i915_irq.c | 11 +++++------
>  1 file changed, 5 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
> index 2d76183..bfd21c7 100644
> --- a/drivers/gpu/drm/i915/i915_irq.c
> +++ b/drivers/gpu/drm/i915/i915_irq.c
> @@ -2561,12 +2561,9 @@ static bool
>  ipehr_is_semaphore_wait(struct drm_device *dev, u32 ipehr)
>  {
>  	if (INTEL_INFO(dev)->gen >= 8) {
> -		/*
> -		 * FIXME: gen8 semaphore support - currently we don't emit
> -		 * semaphores on bdw anyway, but this needs to be addressed when
> -		 * we merge that code.
> -		 */
> -		return false;
> +		/* Broadwell's semaphore wait is 3 dwords. We hope IPEHR is the
> +		 * first dword. */
> +		return (ipehr >> 23) == 0x1c;
>  	} else {
>  		ipehr &= ~MI_SEMAPHORE_SYNC_MASK;
>  		return ipehr == (MI_SEMAPHORE_MBOX | MI_SEMAPHORE_COMPARE |
> @@ -2586,6 +2583,8 @@ semaphore_wait_to_signaller_ring(struct intel_ring_buffer *ring, u32 ipehr)
>  		 * FIXME: gen8 semaphore support - currently we don't emit
>  		 * semaphores on bdw anyway, but this needs to be addressed when
>  		 * we merge that code.
> +		 *
> +		 * XXX: Gen8 needs more than just IPEHR.
>  		 */

I believe something like this should take care of the remaining gap.

diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
index 2446e61..cd1069e 100644
--- a/drivers/gpu/drm/i915/i915_irq.c
+++ b/drivers/gpu/drm/i915/i915_irq.c
@@ -2590,19 +2590,21 @@ ipehr_is_semaphore_wait(struct drm_device *dev, u32 ipehr)
 }
 
 static struct intel_ring_buffer *
-semaphore_wait_to_signaller_ring(struct intel_ring_buffer *ring, u32 ipehr)
+semaphore_wait_to_signaller_ring(struct intel_ring_buffer *ring,
+				 u32 ipehr, u64 offset)
 {
 	struct drm_i915_private *dev_priv = ring->dev->dev_private;
 	struct intel_ring_buffer *signaller;
 	int i;
 
 	if (INTEL_INFO(dev_priv->dev)->gen >= 8) {
-		/*
-		 * FIXME: gen8 semaphore support - currently we don't emit
-		 * semaphores on bdw anyway, but this needs to be addressed when
-		 * we merge that code.
-		 */
-		return NULL;
+		for_each_ring(signaller, dev_priv, i) {
+			if (ring == signaller)
+				continue;
+
+			if (offset == signaller->semaphore.signal_gtt[ring->id])
+				return signaller;
+		}
 	} else {
 		u32 sync_bits = ipehr & MI_SEMAPHORE_SYNC_MASK;
 
@@ -2627,6 +2629,7 @@ semaphore_waits_for(struct intel_ring_buffer *ring, u32 *seqno)
 {
 	struct drm_i915_private *dev_priv = ring->dev->dev_private;
 	u32 cmd, ipehr, head;
+	u64 offset = 0;
 	int i;
 
 	ipehr = I915_READ(RING_IPEHR(ring->mmio_base));
@@ -2662,7 +2665,12 @@ semaphore_waits_for(struct intel_ring_buffer *ring, u32 *seqno)
 		return NULL;
 
 	*seqno = ioread32(ring->virtual_start + head + 4) + 1;
-	return semaphore_wait_to_signaller_ring(ring, ipehr);
+	if (INTEL_INFO(dev_priv->dev)->gen >= 8) {
+		offset = ioread32(ring->virtual_start + head + 12);
+		offset <<= 32;
+		offset |= ioread32(ring->virtual_start + head + 8);
+	}
+	return semaphore_wait_to_signaller_ring(ring, ipehr, offset);
 }
 
 static int semaphore_passed(struct intel_ring_buffer *ring)
-- 
1.8.3.2


>  		return NULL;
>  	} else {
> -- 
> 1.9.2
> 
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-- 
Ville Syrjälä
Intel OTC