Attachment 56749 Details for Bug 45492 – Revert use of autoreported head

[patch] Revert use of autoreported head

0001-drm-i915-Remove-use-of-the-autoreported-ringbuffer-H.patch (text/plain), 3.07 KB, created by Chris Wilson on 2012-02-08 06:25:31 UTC

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Creator: Chris Wilson

Created: 2012-02-08 06:25:31 UTC

Size: 3.07 KB

patch

obsolete

>From d7ab5cc9631c29eb58da4ab803d62344220cf8b8 Mon Sep 17 00:00:00 2001
>From: Chris Wilson <chris@chris-wilson.co.uk>
>Date: Wed, 1 Feb 2012 18:25:28 +0000
>Subject: [PATCH 1/2] drm/i915: Remove use of the autoreported ringbuffer HEAD
> position
>
>This is a revert of 6aa56062eaba67adfb247cded244fd877329588d.
>
>This was originally introduced to workaround reads of the ringbuffer
>registers returning 0 on SandyBridge causing hangs due to ringbuffer
>overflow. The root cause here was reads through the GT powerwell require
>the forcewake dance, something we only learnt of later. Now it appears
>that reading the reported head position from the HWS is returning
>garbage, leading once again to hangs.
>
>For example, on q35 the autoreported head reports:
>  [  217.975608] head now 00010000, actual 00010000
>  [  436.725613] head now 00200000, actual 00200000
>  [  462.956033] head now 00210000, actual 00210010
>  [  485.501409] head now 00400000, actual 00400020
>  [  508.064280] head now 00410000, actual 00410000
>  [  530.576078] head now 00600000, actual 00600020
>  [  553.273489] head now 00610000, actual 00610018
>which appears reasonably sane. In contrast, if we look at snb:
>  [  141.970680] head now 00e10000, actual 00008238
>  [  141.974062] head now 02734000, actual 000083c8
>  [  141.974425] head now 00e10000, actual 00008488
>  [  141.980374] head now 032b5000, actual 000088b8
>  [  141.980885] head now 03271000, actual 00008950
>  [  142.040628] head now 02101000, actual 00008b40
>  [  142.180173] head now 02734000, actual 00009050
>  [  142.181090] head now 00000000, actual 00000ae0
>  [  142.183737] head now 02734000, actual 00009050
>
>In addition, the automatic reporting of the head position is scheduled
>to be defeatured in the future. It has no more utility, remove it.
>
>Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=45492
>Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
>---
> drivers/gpu/drm/i915/intel_ringbuffer.c |   14 +-------------
> 1 files changed, 1 insertions(+), 13 deletions(-)
>
>diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
>index 023739f..620b2ed 100644
>--- a/drivers/gpu/drm/i915/intel_ringbuffer.c
>+++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
>@@ -287,7 +287,7 @@ static int init_ring_common(struct intel_ring_buffer *ring)
> 
> 	I915_WRITE_CTL(ring,
> 			((ring->size - PAGE_SIZE) & RING_NR_PAGES)
>-			| RING_REPORT_64K | RING_VALID);
>+			| RING_VALID);
> 
> 	/* If the head is still not zero, the ring is dead */
> 	if ((I915_READ_CTL(ring) & RING_VALID) == 0 ||
>@@ -1059,18 +1059,6 @@ int intel_wait_ring_buffer(struct intel_ring_buffer *ring, int n)
> 	struct drm_device *dev = ring->dev;
> 	struct drm_i915_private *dev_priv = dev->dev_private;
> 	unsigned long end;
>-	u32 head;
>-
>-	/* If the reported head position has wrapped or hasn't advanced,
>-	 * fallback to the slow and accurate path.
>-	 */
>-	head = intel_read_status_page(ring, 4);
>-	if (head > ring->head) {
>-		ring->head = head;
>-		ring->space = ring_space(ring);
>-		if (ring->space >= n)
>-			return 0;
>-	}
> 
> 	trace_i915_ring_wait_begin(ring);
> 	if (drm_core_check_feature(dev, DRIVER_GEM))
>-- 
>1.7.9
>

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Attachments on bug 45492: 56439 | 56445 | 56453 | 56463 | 56479 | 56480 | 56481 | 56522 | 56749 | 56750 | 56765

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