drm/i915: re-enable rc6 support for Ironlake+

Re-enable rc6 support on Ironlake for power savings.  Adds a debugfs
file to check current RC state, adds a missing workaround for Ironlake
MI_SET_CONTEXT instructions, and renames MCHBAR_RENDER_STANDBY to
RSTDBYCTL to match the docs.

Keep RC6 and the power context disabled on pre-ILK.  It only seems to
hang and doesn't save any power.

Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

1 files changed, 25 insertions, 1 deletions

diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
index 7243d6418651..9c4cdc143be9 100644
--- a/drivers/gpu/drm/i915/i915_debugfs.c
+++ b/drivers/gpu/drm/i915/i915_debugfs.c
@@ -896,7 +896,7 @@ static int i915_drpc_info(struct seq_file *m, void *unused)
         struct drm_device *dev = node->minor->dev;
         drm_i915_private_t *dev_priv = dev->dev_private;
         u32 rgvmodectl = I915_READ(MEMMODECTL);
-        u32 rstdbyctl = I915_READ(MCHBAR_RENDER_STANDBY);
+        u32 rstdbyctl = I915_READ(RSTDBYCTL);
         u16 crstandvid = I915_READ16(CRSTANDVID);
 
         seq_printf(m, "HD boost: %s\n", (rgvmodectl & MEMMODE_BOOST_EN) ?
@@ -919,6 +919,30 @@ static int i915_drpc_info(struct seq_file *m, void *unused)
         seq_printf(m, "RS2 VID: %d\n", ((crstandvid >> 8) & 0x3f));
         seq_printf(m, "Render standby enabled: %s\n",
                    (rstdbyctl & RCX_SW_EXIT) ? "no" : "yes");
+        seq_printf(m, "Current RS state: ");
+        switch (rstdbyctl & RSX_STATUS_MASK) {
+        case RSX_STATUS_ON:
+                seq_printf(m, "on\n");
+                break;
+        case RSX_STATUS_RC1:
+                seq_printf(m, "RC1\n");
+                break;
+        case RSX_STATUS_RC1E:
+                seq_printf(m, "RC1E\n");
+                break;
+        case RSX_STATUS_RS1:
+                seq_printf(m, "RS1\n");
+                break;
+        case RSX_STATUS_RS2:
+                seq_printf(m, "RS2 (RC6)\n");
+                break;
+        case RSX_STATUS_RS3:
+                seq_printf(m, "RC3 (RC6+)\n");
+                break;
+        default:
+                seq_printf(m, "unknown\n");
+                break;
+        }
 
         return 0;
 }