[PATCH] drm/i915: support overclocking on Sandy Bridge

[Jesse Barnes <jbarnes@virtuousgeek.org>]

In some configuration, the PCU may allow us to overclock the GPU.
Check for this case and adjust the max frequency as appropriate.  Also
initialize the min/max frequencies to default values as indicated by
hardware.

Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>

diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index d60860e..4e97af1 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -3229,6 +3229,7 @@
 
 #define GEN6_PCODE_MAILBOX			0x138124
 #define   GEN6_PCODE_READY			(1<<31)
+#define   GEN6_READ_OC_PARAMS			0xc
 #define   GEN6_PCODE_WRITE_MIN_FREQ_TABLE	0x9
 #define GEN6_PCODE_DATA				0x138128
 
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index fb4ec3d..70afa5a 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -6128,6 +6128,10 @@ void intel_init_emon(struct drm_device *dev)
 
 void gen6_init_rps(struct drm_i915_private *dev_priv)
 {
+	u32 rp_state_cap = I915_READ(GEN6_RP_STATE_CAP);
+	u32 gt_perf_status = I915_READ(GEN6_GT_PERF_STATUS);
+	u32 pcu_mbox;
+	int cur_freq, min_freq, max_freq;
 	int i;
 
 	/* Here begins a magic sequence of register writes to enable
@@ -6198,6 +6202,29 @@ void gen6_init_rps(struct drm_i915_private *dev_priv)
 		     500))
 		DRM_ERROR("timeout waiting for pcode mailbox to finish\n");
 
+	min_freq = (rp_state_cap & 0xff0000) >> 16;
+	max_freq = rp_state_cap & 0xff;
+	cur_freq = (gt_perf_status & 0xff00) >> 8;
+
+	/* Check for overclock support */
+	if (wait_for((I915_READ(GEN6_PCODE_MAILBOX) & GEN6_PCODE_READY) == 0,
+		     500))
+		DRM_ERROR("timeout waiting for pcode mailbox to become idle\n");
+	I915_WRITE(GEN6_PCODE_MAILBOX, GEN6_READ_OC_PARAMS);
+	pcu_mbox = I915_READ(GEN6_PCODE_DATA);
+	if (wait_for((I915_READ(GEN6_PCODE_MAILBOX) & GEN6_PCODE_READY) == 0,
+		     500))
+		DRM_ERROR("timeout waiting for pcode mailbox to finish\n");
+	if (pcu_mbox & (1<<31)) { /* OC supported */
+		max_freq = pcu_mbox & 0xff;
+		DRM_DEBUG_DRIVER("overclocking supported, adjusting frequency max to %dMHz\n", pcu_mbox * 100);
+	}
+
+	/* In units of 100MHz */
+	dev_priv->max_delay = max_freq;
+	dev_priv->min_delay = min_freq;
+	dev_priv->cur_delay = cur_freq;
+
 	/* requires MSI enabled */
 	I915_WRITE(GEN6_PMIER,
 		   GEN6_PM_MBOX_EVENT |