drm/i915: enable ppgtt

We want to unconditionally enable ppgtt for two reasons:
- Windows uses this on snb and later.
- We need the basic hw support to work before we can think about real
  per-process address spaces and other cool features we want.

But Chris Wilson was complaining all over irc and intel-gfx that this
will blow up if we don't have a module option to disable it. Hence add
one, to prevent this.

ppgtt support seems to slightly change the timings and make crashy
things slightly more or less crashy. Now in my testing and the testing
this got on troublesome snb machines, it seems to have improved things
only. But on ivb it makes quite a few crashes happen much more often,
see

https://bugs.freedesktop.org/show_bug.cgi?id=41353

Luckily Eugeni Dodonov seems to have a set of workarounds that fix
this issue.

v2: Don't try to enable ppgtt on pre-snb.

v3: Pimp commit message and make Chris Wilson less grumpy by adding a
module option.

v4: New try at making Chris Wilson happy.
Reviewed-by: Ben Widawsky <ben@bwidawsk.net>
Acked-by: Chris Wilson <chris@chris-wilson.co.uk>
Tested-by: Chris Wilson <chris@chris-wilson.co.uk>
Tested-by: Eugeni Dodonov <eugeni.dodonov@intel.com>
Reviewed-by: Eugeni Dodonov <eugeni.dodonov@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_dma.c

@@ -1196,7 +1196,7 @@ static int i915_load_gem_init(struct drm_device *dev)
 	/* Basic memrange allocator for stolen space */
 	drm_mm_init(&dev_priv->mm.stolen, 0, prealloc_size);
 
-	if (HAS_ALIASING_PPGTT(dev)) {
+	if (i915_enable_ppgtt && HAS_ALIASING_PPGTT(dev)) {
 		/* PPGTT pdes are stolen from global gtt ptes, so shrink the
 		 * aperture accordingly when using aliasing ppgtt. */
 		gtt_size -= I915_PPGTT_PD_ENTRIES*PAGE_SIZE;

drivers/gpu/drm/i915/i915_drv.c

@@ -103,6 +103,11 @@ MODULE_PARM_DESC(enable_hangcheck,
 		"WARNING: Disabling this can cause system wide hangs. "
 		"(default: true)");
 
+bool i915_enable_ppgtt __read_mostly = 1;
+module_param_named(i915_enable_ppgtt, i915_enable_ppgtt, bool, 0600);
+MODULE_PARM_DESC(i915_enable_ppgtt,
+		"Enable PPGTT (default: true)");
+
 static struct drm_driver driver;
 extern int intel_agp_enabled;
 
@@ -694,6 +699,8 @@ int i915_reset(struct drm_device *dev, u8 flags)
 		if (HAS_BLT(dev))
 		    dev_priv->ring[BCS].init(&dev_priv->ring[BCS]);
 
+		i915_gem_init_ppgtt(dev);
+
 		mutex_unlock(&dev->struct_mutex);
 		drm_irq_uninstall(dev);
 		drm_mode_config_reset(dev);

drivers/gpu/drm/i915/i915_drv.h

@@ -1032,6 +1032,7 @@ extern int i915_vbt_sdvo_panel_type __read_mostly;
 extern int i915_enable_rc6 __read_mostly;
 extern int i915_enable_fbc __read_mostly;
 extern bool i915_enable_hangcheck __read_mostly;
+extern bool i915_enable_ppgtt __read_mostly;
 
 extern int i915_suspend(struct drm_device *dev, pm_message_t state);
 extern int i915_resume(struct drm_device *dev);
@@ -1210,6 +1211,7 @@ int __must_check i915_gem_object_set_domain(struct drm_i915_gem_object *obj,
 int __must_check i915_gem_object_finish_gpu(struct drm_i915_gem_object *obj);
 int __must_check i915_gem_init_hw(struct drm_device *dev);
 void i915_gem_init_swizzling(struct drm_device *dev);
+void i915_gem_init_ppgtt(struct drm_device *dev);
 void i915_gem_cleanup_ringbuffer(struct drm_device *dev);
 void i915_gem_do_init(struct drm_device *dev,
 		      unsigned long start,

drivers/gpu/drm/i915/i915_gem.c

@@ -3712,6 +3712,43 @@ void i915_gem_init_swizzling(struct drm_device *dev)
 	else
 		I915_WRITE(ARB_MODE, ARB_MODE_ENABLE(ARB_MODE_SWIZZLE_IVB));
 }
+
+void i915_gem_init_ppgtt(struct drm_device *dev)
+{
+	drm_i915_private_t *dev_priv = dev->dev_private;
+	uint32_t pd_offset;
+	struct intel_ring_buffer *ring;
+	int i;
+
+	if (!dev_priv->mm.aliasing_ppgtt)
+		return;
+
+	pd_offset = dev_priv->mm.aliasing_ppgtt->pd_offset;
+	pd_offset /= 64; /* in cachelines, */
+	pd_offset <<= 16;
+
+	if (INTEL_INFO(dev)->gen == 6) {
+		uint32_t ecochk = I915_READ(GAM_ECOCHK);
+		I915_WRITE(GAM_ECOCHK, ecochk | ECOCHK_SNB_BIT |
+				       ECOCHK_PPGTT_CACHE64B);
+		I915_WRITE(GFX_MODE, GFX_MODE_ENABLE(GFX_PPGTT_ENABLE));
+	} else if (INTEL_INFO(dev)->gen >= 7) {
+		I915_WRITE(GAM_ECOCHK, ECOCHK_PPGTT_CACHE64B);
+		/* GFX_MODE is per-ring on gen7+ */
+	}
+
+	for (i = 0; i < I915_NUM_RINGS; i++) {
+		ring = &dev_priv->ring[i];
+
+		if (INTEL_INFO(dev)->gen >= 7)
+			I915_WRITE(RING_MODE_GEN7(ring),
+				   GFX_MODE_ENABLE(GFX_PPGTT_ENABLE));
+
+		I915_WRITE(RING_PP_DIR_DCLV(ring), PP_DIR_DCLV_2G);
+		I915_WRITE(RING_PP_DIR_BASE(ring), pd_offset);
+	}
+}
+
 int
 i915_gem_init_hw(struct drm_device *dev)
 {
@@ -3738,6 +3775,8 @@ i915_gem_init_hw(struct drm_device *dev)
 
 	dev_priv->next_seqno = 1;
 
+	i915_gem_init_ppgtt(dev);
+
 	return 0;
 
 cleanup_bsd_ring: