drm/i915: Extract PCU communication

There is a special mechanism for communicating with the PCU already
being used for the ring frequency stuff. As we'll be needing this for
other commands, extract it now to make future code less error prone and
the current code more reusable.

I'm not entirely sure if this code matches 1:1 with the previous code
behaviorally. Functionally however, it should be the same.

CC: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org>
[danvet: Fixup compile fail reported by Wu Fengguang.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index 07da990..0cc7dbf 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -2407,7 +2407,7 @@
 	u32 pcu_mbox, rc6_mask = 0;
 	u32 gtfifodbg;
 	int rc6_mode;
-	int i;
+	int i, ret;
 
 	WARN_ON(!mutex_is_locked(&dev->struct_mutex));
 
@@ -2503,30 +2503,16 @@
 		   GEN6_RP_UP_BUSY_AVG |
 		   (IS_HASWELL(dev) ? GEN7_RP_DOWN_IDLE_AVG : GEN6_RP_DOWN_IDLE_CONT));
 
-	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_DATA, 0);
-	I915_WRITE(GEN6_PCODE_MAILBOX,
-		   GEN6_PCODE_READY |
-		   GEN6_PCODE_WRITE_MIN_FREQ_TABLE);
-	if (wait_for((I915_READ(GEN6_PCODE_MAILBOX) & GEN6_PCODE_READY) == 0,
-		     500))
-		DRM_ERROR("timeout waiting for pcode mailbox to finish\n");
-
-	/* 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 */
-		dev_priv->rps.max_delay = pcu_mbox & 0xff;
-		DRM_DEBUG_DRIVER("overclocking supported, adjusting frequency max to %dMHz\n", pcu_mbox * 50);
+	ret = sandybridge_pcode_write(dev_priv, GEN6_PCODE_WRITE_MIN_FREQ_TABLE, 0);
+	if (!ret) {
+		pcu_mbox = 0;
+		ret = sandybridge_pcode_read(dev_priv, GEN6_READ_OC_PARAMS, &pcu_mbox);
+		if (ret && pcu_mbox & (1<<31)) { /* OC supported */
+			dev_priv->rps.max_delay = pcu_mbox & 0xff;
+			DRM_DEBUG_DRIVER("overclocking supported, adjusting frequency max to %dMHz\n", pcu_mbox * 50);
+		}
+	} else {
+		DRM_DEBUG_DRIVER("Failed to set the min frequency\n");
 	}
 
 	gen6_set_rps(dev_priv->dev, (gt_perf_status & 0xff00) >> 8);
@@ -2581,17 +2567,11 @@
 		else
 			ia_freq = max_ia_freq - ((diff * scaling_factor) / 2);
 		ia_freq = DIV_ROUND_CLOSEST(ia_freq, 100);
+		ia_freq <<= GEN6_PCODE_FREQ_IA_RATIO_SHIFT;
 
-		I915_WRITE(GEN6_PCODE_DATA,
-			   (ia_freq << GEN6_PCODE_FREQ_IA_RATIO_SHIFT) |
-			   gpu_freq);
-		I915_WRITE(GEN6_PCODE_MAILBOX, GEN6_PCODE_READY |
-			   GEN6_PCODE_WRITE_MIN_FREQ_TABLE);
-		if (wait_for((I915_READ(GEN6_PCODE_MAILBOX) &
-			      GEN6_PCODE_READY) == 0, 10)) {
-			DRM_ERROR("pcode write of freq table timed out\n");
-			continue;
-		}
+		sandybridge_pcode_write(dev_priv,
+					GEN6_PCODE_WRITE_MIN_FREQ_TABLE,
+					ia_freq | gpu_freq);
 	}
 }
 
@@ -4152,3 +4132,49 @@
 	}
 }
 
+int sandybridge_pcode_read(struct drm_i915_private *dev_priv, u8 mbox, u32 *val)
+{
+	WARN_ON(!mutex_is_locked(&dev_priv->dev->struct_mutex));
+
+	if (I915_READ(GEN6_PCODE_MAILBOX) & GEN6_PCODE_READY) {
+		DRM_DEBUG_DRIVER("warning: pcode (read) mailbox access failed\n");
+		return -EAGAIN;
+	}
+
+	I915_WRITE(GEN6_PCODE_DATA, *val);
+	I915_WRITE(GEN6_PCODE_MAILBOX, GEN6_PCODE_READY | mbox);
+
+	if (wait_for((I915_READ(GEN6_PCODE_MAILBOX) & GEN6_PCODE_READY) == 0,
+		     500)) {
+		DRM_ERROR("timeout waiting for pcode read (%d) to finish\n", mbox);
+		return -ETIMEDOUT;
+	}
+
+	*val = I915_READ(GEN6_PCODE_DATA);
+	I915_WRITE(GEN6_PCODE_DATA, 0);
+
+	return 0;
+}
+
+int sandybridge_pcode_write(struct drm_i915_private *dev_priv, u8 mbox, u32 val)
+{
+	WARN_ON(!mutex_is_locked(&dev_priv->dev->struct_mutex));
+
+	if (I915_READ(GEN6_PCODE_MAILBOX) & GEN6_PCODE_READY) {
+		DRM_DEBUG_DRIVER("warning: pcode (write) mailbox access failed\n");
+		return -EAGAIN;
+	}
+
+	I915_WRITE(GEN6_PCODE_DATA, val);
+	I915_WRITE(GEN6_PCODE_MAILBOX, GEN6_PCODE_READY | mbox);
+
+	if (wait_for((I915_READ(GEN6_PCODE_MAILBOX) & GEN6_PCODE_READY) == 0,
+		     500)) {
+		DRM_ERROR("timeout waiting for pcode write (%d) to finish\n", mbox);
+		return -ETIMEDOUT;
+	}
+
+	I915_WRITE(GEN6_PCODE_DATA, 0);
+
+	return 0;
+}