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From: Ben Widawsky <ben@bwidawsk.net>
To: intel-gfx@lists.freedesktop.org
Subject: [PATCH 2/4] drm/i915: refcounts for forcewake
Date: Mon, 11 Apr 2011 18:01:17 -0700	[thread overview]
Message-ID: <1302570079-17032-3-git-send-email-ben@bwidawsk.net> (raw)
In-Reply-To: <1302570079-17032-1-git-send-email-ben@bwidawsk.net>

The reference count provides a clean way for userspace to gain access to
correct register reads and writes by initiating forcewake.

The mechanism also makes it possible to limit the time struct_mutex is
held on register reads and writes to the time it takes to obtain a
reference. However there is no safe use-case for this yet as register
reads and writes are currently expected to be protected by a mutex.

Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
---
 drivers/gpu/drm/i915/i915_debugfs.c  |   10 ++++++++--
 drivers/gpu/drm/i915/i915_drv.c      |   20 ++++++++++++++++++--
 drivers/gpu/drm/i915/i915_drv.h      |   10 ++++++----
 drivers/gpu/drm/i915/intel_display.c |    8 ++++----
 4 files changed, 36 insertions(+), 12 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
index 87c8e29..2edb8b2 100644
--- a/drivers/gpu/drm/i915/i915_debugfs.c
+++ b/drivers/gpu/drm/i915/i915_debugfs.c
@@ -852,6 +852,7 @@ static int i915_cur_delayinfo(struct seq_file *m, void *unused)
 	struct drm_info_node *node = (struct drm_info_node *) m->private;
 	struct drm_device *dev = node->minor->dev;
 	drm_i915_private_t *dev_priv = dev->dev_private;
+	int ret;
 
 	if (IS_GEN5(dev)) {
 		u16 rgvswctl = I915_READ16(MEMSWCTL);
@@ -873,7 +874,11 @@ static int i915_cur_delayinfo(struct seq_file *m, void *unused)
 		int max_freq;
 
 		/* RPSTAT1 is in the GT power well */
-		__gen6_gt_force_wake_get(dev_priv);
+		ret = mutex_lock_interruptible(&dev->struct_mutex);
+		if (ret)
+			return ret;
+
+		gen6_gt_force_wake_get(dev_priv);
 
 		rpstat = I915_READ(GEN6_RPSTAT1);
 		rpupei = I915_READ(GEN6_RP_CUR_UP_EI);
@@ -918,7 +923,8 @@ static int i915_cur_delayinfo(struct seq_file *m, void *unused)
 		seq_printf(m, "Max non-overclocked (RP0) frequency: %dMHz\n",
 			   max_freq * 50);
 
-		__gen6_gt_force_wake_put(dev_priv);
+		gen6_gt_force_wake_put(dev_priv);
+		mutex_unlock(&dev->struct_mutex);
 	} else {
 		seq_printf(m, "no P-state info available\n");
 	}
diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
index c34a8dd..ce59cd4 100644
--- a/drivers/gpu/drm/i915/i915_drv.c
+++ b/drivers/gpu/drm/i915/i915_drv.c
@@ -263,7 +263,7 @@ void intel_detect_pch (struct drm_device *dev)
 	}
 }
 
-void __gen6_gt_force_wake_get(struct drm_i915_private *dev_priv)
+static void __gen6_gt_force_wake_get(struct drm_i915_private *dev_priv)
 {
 	int count;
 
@@ -279,12 +279,28 @@ void __gen6_gt_force_wake_get(struct drm_i915_private *dev_priv)
 		udelay(10);
 }
 
-void __gen6_gt_force_wake_put(struct drm_i915_private *dev_priv)
+void gen6_gt_force_wake_get(struct drm_i915_private *dev_priv)
+{
+	WARN_ON(!mutex_is_locked(&dev_priv->dev->struct_mutex));
+
+	if (dev_priv->forcewake_count++ == 0)
+		__gen6_gt_force_wake_get(dev_priv);
+}
+
+static void __gen6_gt_force_wake_put(struct drm_i915_private *dev_priv)
 {
 	I915_WRITE_NOTRACE(FORCEWAKE, 0);
 	POSTING_READ(FORCEWAKE);
 }
 
+void gen6_gt_force_wake_put(struct drm_i915_private *dev_priv)
+{
+	WARN_ON(!mutex_is_locked(&dev_priv->dev->struct_mutex));
+
+	if (--dev_priv->forcewake_count == 0)
+		__gen6_gt_force_wake_put(dev_priv);
+}
+
 void __gen6_gt_wait_for_fifo(struct drm_i915_private *dev_priv)
 {
 	int loop = 500;
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 8981173..f024927 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -703,6 +703,8 @@ typedef struct drm_i915_private {
 	struct intel_fbdev *fbdev;
 
 	struct drm_property *broadcast_rgb_property;
+
+	int forcewake_count;
 } drm_i915_private_t;
 
 struct drm_i915_gem_object {
@@ -1318,8 +1320,8 @@ extern void intel_display_print_error_state(struct seq_file *m,
  * must be set to prevent GT core from power down and stale values being
  * returned.
  */
-void __gen6_gt_force_wake_get(struct drm_i915_private *dev_priv);
-void __gen6_gt_force_wake_put(struct drm_i915_private *dev_priv);
+void gen6_gt_force_wake_get(struct drm_i915_private *dev_priv);
+void gen6_gt_force_wake_put(struct drm_i915_private *dev_priv);
 void __gen6_gt_wait_for_fifo(struct drm_i915_private *dev_priv);
 
 /* We give fast paths for the really cool registers */
@@ -1332,9 +1334,9 @@ void __gen6_gt_wait_for_fifo(struct drm_i915_private *dev_priv);
 static inline u##x i915_read##x(struct drm_i915_private *dev_priv, u32 reg) { \
 	u##x val = 0; \
 	if (NEEDS_FORCE_WAKE((dev_priv), (reg))) { \
-		__gen6_gt_force_wake_get(dev_priv); \
+		gen6_gt_force_wake_get(dev_priv); \
 		val = read##y(dev_priv->regs + reg); \
-		__gen6_gt_force_wake_put(dev_priv); \
+		gen6_gt_force_wake_put(dev_priv); \
 	} else { \
 		val = read##y(dev_priv->regs + reg); \
 	} \
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 432fc04..4585005 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -1828,7 +1828,7 @@ static void sandybridge_blit_fbc_update(struct drm_device *dev)
 	u32 blt_ecoskpd;
 
 	/* Make sure blitter notifies FBC of writes */
-	__gen6_gt_force_wake_get(dev_priv);
+	gen6_gt_force_wake_get(dev_priv);
 	blt_ecoskpd = I915_READ(GEN6_BLITTER_ECOSKPD);
 	blt_ecoskpd |= GEN6_BLITTER_FBC_NOTIFY <<
 		GEN6_BLITTER_LOCK_SHIFT;
@@ -1839,7 +1839,7 @@ static void sandybridge_blit_fbc_update(struct drm_device *dev)
 			 GEN6_BLITTER_LOCK_SHIFT);
 	I915_WRITE(GEN6_BLITTER_ECOSKPD, blt_ecoskpd);
 	POSTING_READ(GEN6_BLITTER_ECOSKPD);
-	__gen6_gt_force_wake_put(dev_priv);
+	gen6_gt_force_wake_put(dev_priv);
 }
 
 static void ironlake_enable_fbc(struct drm_crtc *crtc, unsigned long interval)
@@ -6853,7 +6853,7 @@ void gen6_enable_rps(struct drm_i915_private *dev_priv)
 	 * userspace...
 	 */
 	I915_WRITE(GEN6_RC_STATE, 0);
-	__gen6_gt_force_wake_get(dev_priv);
+	gen6_gt_force_wake_get(dev_priv);
 
 	/* disable the counters and set deterministic thresholds */
 	I915_WRITE(GEN6_RC_CONTROL, 0);
@@ -6951,7 +6951,7 @@ void gen6_enable_rps(struct drm_i915_private *dev_priv)
 	/* enable all PM interrupts */
 	I915_WRITE(GEN6_PMINTRMSK, 0);
 
-	__gen6_gt_force_wake_put(dev_priv);
+	gen6_gt_force_wake_put(dev_priv);
 }
 
 void intel_enable_clock_gating(struct drm_device *dev)
-- 
1.7.3.4

  parent reply	other threads:[~2011-04-12  1:01 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-04-12  1:01 force wake reference counting (another try) Ben Widawsky
2011-04-12  1:01 ` [PATCH 1/4] drm/i915: proper use of forcewake Ben Widawsky
2011-04-12  1:01 ` Ben Widawsky [this message]
2011-04-12  1:01 ` [PATCH 3/4] drm/i915: userspace interface to the forcewake refcount Ben Widawsky
2011-04-12  1:01 ` [PATCH 4/4] drm/i915: fewer warning patch (temporary) Ben Widawsky
2011-04-12  8:02 ` force wake reference counting (another try) Chris Wilson
2011-04-12 16:30   ` Ben Widawsky
2011-04-12 16:56     ` Keith Packard
2011-04-12 17:21       ` Chris Wilson
2011-04-12 17:41         ` Keith Packard
2011-04-13  1:31           ` Ben Widawsky
2011-04-13  5:31             ` Keith Packard
2011-04-13  5:52             ` Chris Wilson
2011-04-13  6:35               ` Ben Widawsky
  -- strict thread matches above, loose matches on Subject: below --
2011-04-08 17:47 forcewake junk, RFC, RFT(test) Ben Widawsky
2011-04-08 17:47 ` [PATCH 2/4] drm/i915: refcounts for forcewake Ben Widawsky
2011-04-09 20:26 ` forcewake junk, part2 Ben Widawsky
2011-04-09 20:26   ` (no subject) Ben Widawsky
     [not found]     ` <1302380787-2957-3-git-send-email-ben@bwidawsk.net>
2011-04-09 20:26       ` [PATCH 1/4] drm/i915: proper use of forcewake Ben Widawsky
2011-04-09 20:26         ` [PATCH 2/4] drm/i915: refcounts for forcewake Ben Widawsky
2011-04-09 20:31 ` forcewake patches (ignore previous, please) Ben Widawsky
2011-04-09 20:31   ` [PATCH 1/4] drm/i915: proper use of forcewake Ben Widawsky
2011-04-09 20:31     ` [PATCH 2/4] drm/i915: refcounts for forcewake Ben Widawsky

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