Attachment 41814 Details for Bug 30364 – Use PM QoS to prevent C-State starvation of gen3 GPU for 2.6.37

[patch] Use PM QoS to prevent C-State starvation of gen3 GPU for 2.6.37

i915-Use-PM-QoS-to-prevent-C-state-starvation-of-gen3-GPU-2.6.37.patch (text/plain), 4.02 KB, created by Alexander Lam on 2011-01-09 13:16:00 UTC

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Creator: Alexander Lam

Created: 2011-01-09 13:16:00 UTC

Size: 4.02 KB

patch

obsolete

>from https://bugs.freedesktop.org/show_bug.cgi?id=30364
>From b2307cc0f08e908cadf96ae88332844d77472b65 Mon Sep 17 00:00:00 2001
>From: Chris Wilson <chris@chris-wilson.co.uk>
>Date: Sun, 9 Jan 2011 12:04:40 +0000
>Subject: [PATCH] drm/i915: Use PM QoS to prevent C-State starvation of gen3 GPU
>
>945 class hardware has an interesting quirk in which the vblank
>interrupt is not raised if the CPU is in a low power state. (We also
>suspect that the memory bus is clocked to the CPU/c-state and not the
>GPU so there are secondary starvation issues.) In order to prevent the
>most obvious issue of the low of the vblank interrupt (stuttering
>compositing that only updates when the mouse is moving) is to install a
>PM QoS request to prevent low c-states whilst the GPU is active.
>
>Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
>---
> drivers/gpu/drm/i915/i915_drv.h |    5 +++++
> drivers/gpu/drm/i915/i915_irq.c |   33 +++++++++++++++++++++++++++++++++
> 2 files changed, 38 insertions(+), 0 deletions(-)
>
>diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
>index 09de1e9..b0ac99f 100644
>--- a/drivers/gpu/drm/i915/i915_drv.h
>+++ b/drivers/gpu/drm/i915/i915_drv.h
>@@ -35,6 +35,7 @@
> #include "intel_ringbuffer.h"
> #include <linux/io-mapping.h>
> #include <linux/i2c.h>
>+#include <linux/pm_qos_params.h>
> #include <drm/intel-gtt.h>
> 
> /* General customization:
>@@ -308,6 +309,10 @@ typedef struct drm_i915_private {
> 	int vblank_pipe;
> 	int num_pipe;
> 
>+	atomic_t vblank_enabled;
>+	struct pm_qos_request_list vblank_pm_qos;
>+	struct work_struct vblank_work;
>+
> 	/* For hangcheck timer */
> #define DRM_I915_HANGCHECK_PERIOD 1500 /* in ms */
> 	struct timer_list hangcheck_timer;
>diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
>index cf61235..f5601a2 100644
>--- a/drivers/gpu/drm/i915/i915_irq.c
>+++ b/drivers/gpu/drm/i915/i915_irq.c
>@@ -1336,6 +1336,22 @@ int i915_irq_wait(struct drm_device *dev, void *data,
> 	return i915_wait_irq(dev, irqwait->irq_seq);
> }
> 
>+static void i915_vblank_work_func(struct work_struct *work)
>+{
>+	drm_i915_private_t *dev_priv =
>+		container_of(work, drm_i915_private_t, vblank_work);
>+
>+	if (atomic_read(&dev_priv->vblank_enabled)) {
>+		if (!dev_priv->vblank_pm_qos.pm_qos_class)
>+			pm_qos_add_request(&dev_priv->vblank_pm_qos,
>+					   PM_QOS_CPU_DMA_LATENCY,
>+					   15); //>=20 won't work
>+	} else {
>+		if (dev_priv->vblank_pm_qos.pm_qos_class)
>+			pm_qos_remove_request(&dev_priv->vblank_pm_qos);
>+	}
>+}
>+
> /* Called from drm generic code, passed 'crtc' which
>  * we use as a pipe index
>  */
>@@ -1358,6 +1374,16 @@ int i915_enable_vblank(struct drm_device *dev, int pipe)
> 		i915_enable_pipestat(dev_priv, pipe,
> 				     PIPE_VBLANK_INTERRUPT_ENABLE);
> 	spin_unlock_irqrestore(&dev_priv->user_irq_lock, irqflags);
>+
>+	/* gen3 platforms have an issue with vsync interrupts not reaching
>+	 * cpu during deep c-state sleep (>C1), so we need to install a
>+	 * PM QoS handle to prevent C-state starvation of the GPU.
>+	 */
>+	if (dev_priv->info->gen == 3) {
>+		atomic_inc(&dev_priv->vblank_enabled);
>+		queue_work(dev_priv->wq, &dev_priv->vblank_work);
>+	}
>+
> 	return 0;
> }
> 
>@@ -1369,6 +1395,11 @@ void i915_disable_vblank(struct drm_device *dev, int pipe)
> 	drm_i915_private_t *dev_priv = (drm_i915_private_t *) dev->dev_private;
> 	unsigned long irqflags;
> 
>+	if (dev_priv->info->gen == 3) {
>+		atomic_dec(&dev_priv->vblank_enabled);
>+		queue_work(dev_priv->wq, &dev_priv->vblank_work);
>+	}
>+
> 	spin_lock_irqsave(&dev_priv->user_irq_lock, irqflags);
> 	if (HAS_PCH_SPLIT(dev))
> 		ironlake_disable_display_irq(dev_priv, (pipe == 0) ?
>@@ -1658,9 +1689,11 @@ void i915_driver_irq_preinstall(struct drm_device * dev)
> 	drm_i915_private_t *dev_priv = (drm_i915_private_t *) dev->dev_private;
> 
> 	atomic_set(&dev_priv->irq_received, 0);
>+	atomic_set(&dev_priv->vblank_enabled, 0);
> 
> 	INIT_WORK(&dev_priv->hotplug_work, i915_hotplug_work_func);
> 	INIT_WORK(&dev_priv->error_work, i915_error_work_func);
>+	INIT_WORK(&dev_priv->vblank_work, i915_vblank_work_func);
> 
> 	if (HAS_PCH_SPLIT(dev)) {
> 		ironlake_irq_preinstall(dev);
>-- 
>1.7.2.3
>

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Attachments on bug 30364: 38937 | 38938 | 38939 | 39347 | 40923 | 41720 | 41721 | 41796 | 41814 | 42959 | 44065

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