[Intel-gfx] [PATCH] drm/i915: Introduce HSW GT Slice Shutdown on Boot.

[Rodrigo Vivi]

Slice shutdown is a power savings feature whereby parts of HW i.e. slice is
shut off on boot or dynamically to save power.

This patch only introduces a way to disable half of Haswell slices on boot.
Dynamic shutdown is yet to be implemented.

This gt_init already sets MI_PREDICATE_RESULT_2 appropriately.

Signed-off-by: Rodrigo Vivi <rodrigo.vivi at gmail.com>
---
 drivers/gpu/drm/i915/i915_drv.c |  5 +++++
 drivers/gpu/drm/i915/i915_drv.h |  3 +++
 drivers/gpu/drm/i915/i915_reg.h | 16 ++++++++++++++++
 drivers/gpu/drm/i915/intel_pm.c | 23 +++++++++++++++++++++++
 4 files changed, 47 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
index 735dd56..fe89bdc 100644
--- a/drivers/gpu/drm/i915/i915_drv.c
+++ b/drivers/gpu/drm/i915/i915_drv.c
@@ -154,6 +154,11 @@ module_param_named(prefault_disable, i915_prefault_disable, bool, 0600);
 MODULE_PARM_DESC(prefault_disable,
 		"Disable page prefaulting for pread/pwrite/reloc (default:false). For developers only.");
 
+int i915_slice_shutdown __read_mostly = 0;
+module_param_named(slice_shutdown, i915_slice_shutdown, int, 0600);
+MODULE_PARM_DESC(slice_shutdown,
+		 "Disable half of EUs at boot time to save power.");
+
 static struct drm_driver driver;
 extern int intel_agp_enabled;
 
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 05de1ca..796aac7 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -1595,6 +1595,8 @@ struct drm_i915_file_private {
 				 ((dev)->pci_device & 0xFF00) == 0x0C00)
 #define IS_ULT(dev)		(IS_HASWELL(dev) && \
 				 ((dev)->pci_device & 0xFF00) == 0x0A00)
+#define IS_HSW_GT3(dev)		(IS_HASWELL(dev) &&		\
+				 ((dev)->pci_device & 0x00F0) == 0x0020)
 
 /*
  * The genX designation typically refers to the render engine, so render
@@ -1712,6 +1714,7 @@ extern bool i915_fastboot __read_mostly;
 extern int i915_enable_pc8 __read_mostly;
 extern int i915_pc8_timeout __read_mostly;
 extern bool i915_prefault_disable __read_mostly;
+extern int i915_slice_shutdown __read_mostly;
 
 extern int i915_suspend(struct drm_device *dev, pm_message_t state);
 extern int i915_resume(struct drm_device *dev);
diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index 8b81516..9ca93c4 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -278,6 +278,22 @@
 #define  MI_SEMAPHORE_SYNC_VVE	    (1<<16) /* VECS wait for VCS  (VEVSYNC) */
 #define  MI_SEMAPHORE_SYNC_RVE	    (2<<16) /* VECS wait for RCS  (VERSYNC) */
 #define  MI_SEMAPHORE_SYNC_INVALID  (3<<16)
+
+#define MI_PREDICATE_RESULT_2	(0x2214)
+#define  LOWER_SLICE_ENABLED	(1<<0)
+#define  LOWER_SLICE_DISABLED	(0<<0)
+
+#define HSW_GT_SLICE_INFO	0x138064
+#define   SLICE_SEL_BOTH	(1<<3)
+#define   SLICE_AUTOWAKE	(1<<2)
+#define   SLICE_STATUS_MASK	0x3
+#define   SLICE_STATUS_GT_OFF	(0<<0)
+#define   SLICE_STATUS_MAIN_ON	(2<<0)
+#define   SLICE_STATUS_BOTH_ON	(3<<0)
+
+#define HSW_SLICESHUTDOWN	0xA190
+#define   SLICE_SHUTDOWN	(1<<0)
+
 /*
  * 3D instructions used by the kernel
  */
diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index 6b1d003..4301401 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -3617,6 +3617,28 @@ static void gen6_enable_rps(struct drm_device *dev)
 	gen6_gt_force_wake_put(dev_priv);
 }
 
+static void intel_init_gt_slices(struct drm_device *dev)
+{
+	struct drm_i915_private *dev_priv = dev->dev_private;
+
+	if (!IS_HSW_GT3(dev))
+		return;
+
+	if (i915_slice_shutdown) {
+		I915_WRITE(MI_PREDICATE_RESULT_2, LOWER_SLICE_DISABLED);
+		POSTING_READ(MI_PREDICATE_RESULT_2);
+
+		I915_WRITE(HSW_SLICESHUTDOWN, SLICE_SHUTDOWN);
+		POSTING_READ(HSW_SLICESHUTDOWN);
+
+		I915_WRITE(HSW_GT_SLICE_INFO, ~SLICE_SEL_BOTH);
+		POSTING_READ(HSW_GT_SLICE_INFO);
+	} else {
+		I915_WRITE(MI_PREDICATE_RESULT_2, LOWER_SLICE_ENABLED);
+		POSTING_READ(MI_PREDICATE_RESULT_2);
+	}
+}
+
 void gen6_update_ring_freq(struct drm_device *dev)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
@@ -4630,6 +4652,7 @@ static void intel_gen6_powersave_work(struct work_struct *work)
 	} else {
 		gen6_enable_rps(dev);
 		gen6_update_ring_freq(dev);
+		intel_init_gt_slices(dev);
 	}
 	mutex_unlock(&dev_priv->rps.hw_lock);
 }
-- 
1.8.1.4