Attachment 64646 Details for Bug 52424 – use 10 usec delay for snb forcewake ack

[patch] use 10 usec delay for snb forcewake ack

0001-drm-i915-use-a-10-usec-delay-in-forcewake-ack-delay-.patch (text/plain), 6.64 KB, created by Daniel Vetter on 2012-07-25 09:27:02 UTC

(hide)

Description:

Filename:

MIME Type:

Creator: Daniel Vetter

Created: 2012-07-25 09:27:02 UTC

Size: 6.64 KB

patch

obsolete

>From 80374f44e166f61dc42311b21f331437e92cfb71 Mon Sep 17 00:00:00 2001
>From: Daniel Vetter <daniel.vetter@ffwll.ch>
>Date: Wed, 25 Jul 2012 10:57:38 +0200
>Subject: [PATCH] drm/i915: use a 10 usec delay in forcewake ack delay loop
>
>This papers over a regression introduced in
>
>commit 990bbdadabaa51828e475eda86ee5720a4910cc3
>Author: Chris Wilson <chris@chris-wilson.co.uk>
>Date:   Mon Jul 2 11:51:02 2012 -0300
>
>    drm/i915: Group the GT routines together in both code and vtable
>
>which changed the udelay used to wait for the forcewake ack from
>udelay(1) to udelay(10). This broke the use of the Bitstream Decoder
>ring on snb. Some investigation by Chris Wilson showed that a delay
>slightly longer than udelay(1) or just cpu_relax works around this
>issue, so the cpu_relax was used for wait_for_atomic_us (since that
>would speed up the waiting a bit, too).
>
>Unfortunately this caused another regression on snb, completely
>hanging the gpu even when only using glxgears.
>
>To avoid everyone else paying the penalty of the udelay(10) add a
>parameter to the wait_for_atomic_us macro to specifiy the delay. And
>also add a giant comment to the gen6 forcewake code explaining what
>this is all about (note that forcewake_mt is gen7+, hence doesn't need
>this).
>
>Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=51738
>Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=52424
>Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
>---
> drivers/gpu/drm/i915/intel_display.c |    8 ++++----
> drivers/gpu/drm/i915/intel_drv.h     |   21 +++++++++++----------
> drivers/gpu/drm/i915/intel_pm.c      |   15 +++++++++------
> 3 files changed, 24 insertions(+), 20 deletions(-)
>
>diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
>index e9e476e..210b10f 100644
>--- a/drivers/gpu/drm/i915/intel_display.c
>+++ b/drivers/gpu/drm/i915/intel_display.c
>@@ -412,7 +412,7 @@ u32 intel_dpio_read(struct drm_i915_private *dev_priv, int reg)
> 	u32 val = 0;
> 
> 	spin_lock_irqsave(&dev_priv->dpio_lock, flags);
>-	if (wait_for_atomic_us((I915_READ(DPIO_PKT) & DPIO_BUSY) == 0, 100)) {
>+	if (wait_for_atomic_us((I915_READ(DPIO_PKT) & DPIO_BUSY) == 0, 100, 0)) {
> 		DRM_ERROR("DPIO idle wait timed out\n");
> 		goto out_unlock;
> 	}
>@@ -420,7 +420,7 @@ u32 intel_dpio_read(struct drm_i915_private *dev_priv, int reg)
> 	I915_WRITE(DPIO_REG, reg);
> 	I915_WRITE(DPIO_PKT, DPIO_RID | DPIO_OP_READ | DPIO_PORTID |
> 		   DPIO_BYTE);
>-	if (wait_for_atomic_us((I915_READ(DPIO_PKT) & DPIO_BUSY) == 0, 100)) {
>+	if (wait_for_atomic_us((I915_READ(DPIO_PKT) & DPIO_BUSY) == 0, 100, 0)) {
> 		DRM_ERROR("DPIO read wait timed out\n");
> 		goto out_unlock;
> 	}
>@@ -437,7 +437,7 @@ static void intel_dpio_write(struct drm_i915_private *dev_priv, int reg,
> 	unsigned long flags;
> 
> 	spin_lock_irqsave(&dev_priv->dpio_lock, flags);
>-	if (wait_for_atomic_us((I915_READ(DPIO_PKT) & DPIO_BUSY) == 0, 100)) {
>+	if (wait_for_atomic_us((I915_READ(DPIO_PKT) & DPIO_BUSY) == 0, 100, 0)) {
> 		DRM_ERROR("DPIO idle wait timed out\n");
> 		goto out_unlock;
> 	}
>@@ -446,7 +446,7 @@ static void intel_dpio_write(struct drm_i915_private *dev_priv, int reg,
> 	I915_WRITE(DPIO_REG, reg);
> 	I915_WRITE(DPIO_PKT, DPIO_RID | DPIO_OP_WRITE | DPIO_PORTID |
> 		   DPIO_BYTE);
>-	if (wait_for_atomic_us((I915_READ(DPIO_PKT) & DPIO_BUSY) == 0, 100))
>+	if (wait_for_atomic_us((I915_READ(DPIO_PKT) & DPIO_BUSY) == 0, 100, 0))
> 		DRM_ERROR("DPIO write wait timed out\n");
> 
> out_unlock:
>diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
>index 8435355..7e1765b 100644
>--- a/drivers/gpu/drm/i915/intel_drv.h
>+++ b/drivers/gpu/drm/i915/intel_drv.h
>@@ -45,16 +45,17 @@
> 	ret__;								\
> })
> 
>-#define wait_for_atomic_us(COND, US) ({ \
>-	int i, ret__ = -ETIMEDOUT;	\
>-	for (i = 0; i < (US); i++) {	\
>-		if ((COND)) {		\
>-			ret__ = 0;	\
>-			break;		\
>-		}			\
>-		udelay(1);		\
>-	}				\
>-	ret__;				\
>+#define wait_for_atomic_us(COND, US, W) ({ \
>+	unsigned long timeout__ = jiffies + usecs_to_jiffies(US);	\
>+	int ret__ = 0;							\
>+	while (!(COND)) {						\
>+		if (time_after(jiffies, timeout__)) {			\
>+			ret__ = -ETIMEDOUT;				\
>+			break;						\
>+		}							\
>+		if (W) udelay(W) else cpu_relax();						\
>+	}								\
>+	ret__;								\
> })
> 
> #define wait_for(COND, MS) _wait_for(COND, MS, 1)
>diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
>index 94aabca..dc1a9e5 100644
>--- a/drivers/gpu/drm/i915/intel_pm.c
>+++ b/drivers/gpu/drm/i915/intel_pm.c
>@@ -3946,7 +3946,7 @@ static void __gen6_gt_wait_for_thread_c0(struct drm_i915_private *dev_priv)
> 	/* w/a for a sporadic read returning 0 by waiting for the GT
> 	 * thread to wake up.
> 	 */
>-	if (wait_for_atomic_us((I915_READ_NOTRACE(GEN6_GT_THREAD_STATUS_REG) & gt_thread_status_mask) == 0, 500))
>+	if (wait_for_atomic_us((I915_READ_NOTRACE(GEN6_GT_THREAD_STATUS_REG) & gt_thread_status_mask) == 0, 500, 0))
> 		DRM_ERROR("GT thread status wait timed out\n");
> }
> 
>@@ -3959,12 +3959,15 @@ static void __gen6_gt_force_wake_get(struct drm_i915_private *dev_priv)
> 	else
> 		forcewake_ack = FORCEWAKE_ACK;
> 
>-	if (wait_for_atomic_us((I915_READ_NOTRACE(forcewake_ack) & 1) == 0, 500))
>+	/* Note the elephant: If we use anything shorter than udelay(10) in the
>+	 * forcewak ack loops (like udelay(1) or cpu_relax), snb just dies.
>+	 * Cause of this is totally unknown. */
>+	if (wait_for_atomic_us((I915_READ_NOTRACE(forcewake_ack) & 1) == 0, 500, 10))
> 		DRM_ERROR("Force wake wait timed out\n");
> 
> 	I915_WRITE_NOTRACE(FORCEWAKE, 1);
> 
>-	if (wait_for_atomic_us((I915_READ_NOTRACE(forcewake_ack) & 1), 500))
>+	if (wait_for_atomic_us((I915_READ_NOTRACE(forcewake_ack) & 1), 500, 10))
> 		DRM_ERROR("Force wake wait timed out\n");
> 
> 	__gen6_gt_wait_for_thread_c0(dev_priv);
>@@ -3979,12 +3982,12 @@ static void __gen6_gt_force_wake_mt_get(struct drm_i915_private *dev_priv)
> 	else
> 		forcewake_ack = FORCEWAKE_MT_ACK;
> 
>-	if (wait_for_atomic_us((I915_READ_NOTRACE(forcewake_ack) & 1) == 0, 500))
>+	if (wait_for_atomic_us((I915_READ_NOTRACE(forcewake_ack) & 1) == 0, 500, 0))
> 		DRM_ERROR("Force wake wait timed out\n");
> 
> 	I915_WRITE_NOTRACE(FORCEWAKE_MT, _MASKED_BIT_ENABLE(1));
> 
>-	if (wait_for_atomic_us((I915_READ_NOTRACE(forcewake_ack) & 1), 500))
>+	if (wait_for_atomic_us((I915_READ_NOTRACE(forcewake_ack) & 1), 500, 0))
> 		DRM_ERROR("Force wake wait timed out\n");
> 
> 	__gen6_gt_wait_for_thread_c0(dev_priv);
>@@ -4071,7 +4074,7 @@ static void vlv_force_wake_get(struct drm_i915_private *dev_priv)
> 	I915_WRITE_NOTRACE(FORCEWAKE_VLV, 0xffffffff);
> 	POSTING_READ(FORCEWAKE_VLV);
> 
>-	if (wait_for_atomic_us((I915_READ_NOTRACE(FORCEWAKE_ACK_VLV) & 1), 500))
>+	if (wait_for_atomic_us((I915_READ_NOTRACE(FORCEWAKE_ACK_VLV) & 1), 500, 0))
> 		DRM_ERROR("Force wake wait timed out\n");
> 
> 	__gen6_gt_wait_for_thread_c0(dev_priv);
>-- 
>1.7.10.4
>

Actions: View | Splinter Review

Attachments on bug 52424: 64582 | 64646 | 64648 | 64704 | 64706 | 64937 | 65217 | 66255 | 67665 | 68565 | 68772 | 74217 | 74962

Use of freedesktop.org services, including Bugzilla, is subject to our Code of Conduct. How we collect and use information is described in our Privacy Policy.