3 files changed, 42 insertions, 5 deletions

diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
index 1a7559b59997..c7d689e4247c 100644
--- a/drivers/gpu/drm/i915/i915_drv.c
+++ b/drivers/gpu/drm/i915/i915_drv.c
@@ -66,7 +66,11 @@ MODULE_PARM_DESC(semaphores,
 int i915_enable_rc6 __read_mostly = -1;
 module_param_named(i915_enable_rc6, i915_enable_rc6, int, 0600);
 MODULE_PARM_DESC(i915_enable_rc6,
-                "Enable power-saving render C-state 6 (default: -1 (use per-chip default)");
+                "Enable power-saving render C-state 6. "
+                "Different stages can be selected via bitmask values "
+                "(0 = disable; 1 = enable rc6; 2 = enable deep rc6; 4 = enable deepest rc6). "
+                "For example, 3 would enable rc6 and deep rc6, and 7 would enable everything. "
+                "default: -1 (use per-chip default)");
 
 int i915_enable_fbc __read_mostly = -1;
 module_param_named(i915_enable_fbc, i915_enable_fbc, int, 0600);
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index c0f19f572004..2c192270cb0d 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -1053,6 +1053,27 @@ struct drm_i915_file_private {
 
 #include "i915_trace.h"
 
+/**
+ * RC6 is a special power stage which allows the GPU to enter an very
+ * low-voltage mode when idle, using down to 0V while at this stage.  This
+ * stage is entered automatically when the GPU is idle when RC6 support is
+ * enabled, and as soon as new workload arises GPU wakes up automatically as well.
+ *
+ * There are different RC6 modes available in Intel GPU, which differentiate
+ * among each other with the latency required to enter and leave RC6 and
+ * voltage consumed by the GPU in different states.
+ *
+ * The combination of the following flags define which states GPU is allowed
+ * to enter, while RC6 is the normal RC6 state, RC6p is the deep RC6, and
+ * RC6pp is deepest RC6. Their support by hardware varies according to the
+ * GPU, BIOS, chipset and platform. RC6 is usually the safest one and the one
+ * which brings the most power savings; deeper states save more power, but
+ * require higher latency to switch to and wake up.
+ */
+#define INTEL_RC6_ENABLE                        (1<<0)
+#define INTEL_RC6p_ENABLE                       (1<<1)
+#define INTEL_RC6pp_ENABLE                      (1<<2)
+
 extern struct drm_ioctl_desc i915_ioctls[];
 extern int i915_max_ioctl;
 extern unsigned int i915_fbpercrtc __always_unused;
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 078477306975..a0a4e3bcbcf6 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -8221,7 +8221,7 @@ void intel_init_emon(struct drm_device *dev)
         dev_priv->corr = (lcfuse & LCFUSE_HIV_MASK);
 }
 
-static bool intel_enable_rc6(struct drm_device *dev)
+static int intel_enable_rc6(struct drm_device *dev)
 {
         /*
          * Respect the kernel parameter if it is set
@@ -8253,6 +8253,7 @@ void gen6_enable_rps(struct drm_i915_private *dev_priv)
         u32 pcu_mbox, rc6_mask = 0;
         u32 gtfifodbg;
         int cur_freq, min_freq, max_freq;
+        int rc6_mode;
         int i;
 
         /* Here begins a magic sequence of register writes to enable
@@ -8290,9 +8291,20 @@ void gen6_enable_rps(struct drm_i915_private *dev_priv)
         I915_WRITE(GEN6_RC6p_THRESHOLD, 100000);
         I915_WRITE(GEN6_RC6pp_THRESHOLD, 64000); /* unused */
 
-        if (intel_enable_rc6(dev_priv->dev))
-                rc6_mask = GEN6_RC_CTL_RC6_ENABLE |
-                        ((IS_GEN7(dev_priv->dev)) ? GEN6_RC_CTL_RC6p_ENABLE : 0);
+        rc6_mode = intel_enable_rc6(dev_priv->dev);
+        if (rc6_mode & INTEL_RC6_ENABLE)
+                rc6_mask |= GEN6_RC_CTL_RC6_ENABLE;
+
+        if (rc6_mode & INTEL_RC6p_ENABLE)
+                rc6_mask |= GEN6_RC_CTL_RC6p_ENABLE;
+
+        if (rc6_mode & INTEL_RC6pp_ENABLE)
+                rc6_mask |= GEN6_RC_CTL_RC6pp_ENABLE;
+
+        DRM_INFO("Enabling RC6 states: RC6 %s, RC6p %s, RC6pp %s\n",
+                        (rc6_mode & INTEL_RC6_ENABLE) ? "on" : "off",
+                        (rc6_mode & INTEL_RC6p_ENABLE) ? "on" : "off",
+                        (rc6_mode & INTEL_RC6pp_ENABLE) ? "on" : "off");
 
         I915_WRITE(GEN6_RC_CONTROL,
                    rc6_mask |