drm/i915/bxt: reserve space for RC6 in the the GuC WOPCM

This patch resizes the GuC WOPCM (specifically on BXT)
so that the GuC and RC6 memory spaces do not overlap.

v2:
    Made calculation of WOPCM size into a separate function,
    so that it's consistent between the firmware size-check
    and the register-programming operations [Dave Gordon].

Issue: https://jira01.devtools.intel.com/browse/VIZ-6638
Signed-off-by: Peter Antoine <peter.antoine@intel.com>
Signed-off-by: Dave Gordon <david.s.gordon@intel.com>
Reviewed-by: Nick Hoath <nicholas.hoath@intel.com>
Tested-by: Nick Hoath <nicholas.hoath@intel.com>
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1463494365-26330-1-git-send-email-david.s.gordon@intel.com

drivers/gpu/drm/i915/i915_guc_reg.h

@@ -67,11 +67,11 @@
 #define   GUC_WOPCM_OFFSET_VALUE	  0x80000	/* 512KB */
 #define GUC_MAX_IDLE_COUNT		_MMIO(0xC3E4)
 
+/* Defines WOPCM space available to GuC firmware */
 #define GUC_WOPCM_SIZE			_MMIO(0xc050)
-#define   GUC_WOPCM_SIZE_VALUE  	  (0x80 << 12)	/* 512KB */
-
 /* GuC addresses below GUC_WOPCM_TOP don't map through the GTT */
-#define	GUC_WOPCM_TOP			(GUC_WOPCM_SIZE_VALUE)
+#define   GUC_WOPCM_TOP			  (0x80 << 12)	/* 512KB */
+#define   BXT_GUC_WOPCM_RC6_RESERVED	  (0x10 << 12)	/* 64KB  */
 
 #define GEN8_GT_PM_CONFIG		_MMIO(0x138140)
 #define GEN9LP_GT_PM_CONFIG		_MMIO(0x138140)

drivers/gpu/drm/i915/intel_guc_loader.c

@@ -284,6 +284,17 @@ static int guc_ucode_xfer_dma(struct drm_i915_private *dev_priv)
 	return ret;
 }
 
+static u32 guc_wopcm_size(struct drm_i915_private *dev_priv)
+{
+	u32 wopcm_size = GUC_WOPCM_TOP;
+
+	/* On BXT, the top of WOPCM is reserved for RC6 context */
+	if (IS_BROXTON(dev_priv))
+		wopcm_size -= BXT_GUC_WOPCM_RC6_RESERVED;
+
+	return wopcm_size;
+}
+
 /*
  * Load the GuC firmware blob into the MinuteIA.
  */
@@ -311,7 +322,7 @@ static int guc_ucode_xfer(struct drm_i915_private *dev_priv)
 	intel_uncore_forcewake_get(dev_priv, FORCEWAKE_ALL);
 
 	/* init WOPCM */
-	I915_WRITE(GUC_WOPCM_SIZE, GUC_WOPCM_SIZE_VALUE);
+	I915_WRITE(GUC_WOPCM_SIZE, guc_wopcm_size(dev_priv));
 	I915_WRITE(DMA_GUC_WOPCM_OFFSET, GUC_WOPCM_OFFSET_VALUE);
 
 	/* Enable MIA caching. GuC clock gating is disabled. */
@@ -555,9 +566,7 @@ static void guc_fw_fetch(struct drm_device *dev, struct intel_guc_fw *guc_fw)
 
 	/* Header and uCode will be loaded to WOPCM. Size of the two. */
 	size = guc_fw->header_size + guc_fw->ucode_size;
-
-	/* Top 32k of WOPCM is reserved (8K stack + 24k RC6 context). */
-	if (size > GUC_WOPCM_SIZE_VALUE - 0x8000) {
+	if (size > guc_wopcm_size(dev->dev_private)) {
 		DRM_ERROR("Firmware is too large to fit in WOPCM\n");
 		goto fail;
 	}