drm/i915/skl: Determine SKL slice/subslice/EU info

Read fuse registers to determine the available slice total,
subslice total, subslice per slice, EU total, and EU per subslice
counts of the SKL device. The EU per subslice attribute is more
precisely defined as the maximum EU available on any one subslice,
since available EU counts may vary across subslices due to fusing.
Set flags indicating the SKL device's slice/subslice/EU (SSEU)
power gating capability. Make all values available via debugfs
entry 'i915_sseu_status'.

v2: Several small clean-ups suggested by Damien. Most notably,
    used smaller types for the new device info fields to reduce
    memory usage and improved the clarity/readability of the
    method used to extract attribute values from the fuse
    registers.

Signed-off-by: Jeff McGee <jeff.mcgee@intel.com>
Reviewed-by: Damien Lespiau <damien.lespiau@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

1 files changed, 73 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/i915_dma.c b/drivers/gpu/drm/i915/i915_dma.c
index 5804aa5f9df0..9a365b40b50e 100644
--- a/drivers/gpu/drm/i915/i915_dma.c
+++ b/drivers/gpu/drm/i915/i915_dma.c
@@ -606,6 +606,7 @@ static void intel_device_info_runtime_init(struct drm_device *dev)
 		}
 	}
 
+	/* Initialize slice/subslice/EU info */
 	if (IS_CHERRYVIEW(dev)) {
 		u32 fuse, mask_eu;
 
@@ -615,7 +616,79 @@ static void intel_device_info_runtime_init(struct drm_device *dev)
 				  CHV_FGT_EU_DIS_SS1_R0_MASK |
 				  CHV_FGT_EU_DIS_SS1_R1_MASK);
 		info->eu_total = 16 - hweight32(mask_eu);
+	} else if (IS_SKYLAKE(dev)) {
+		const int s_max = 3, ss_max = 4, eu_max = 8;
+		int s, ss;
+		u32 fuse2, eu_disable[s_max], s_enable, ss_disable;
+
+		fuse2 = I915_READ(GEN8_FUSE2);
+		s_enable = (fuse2 & GEN8_F2_S_ENA_MASK) >>
+			   GEN8_F2_S_ENA_SHIFT;
+		ss_disable = (fuse2 & GEN9_F2_SS_DIS_MASK) >>
+			     GEN9_F2_SS_DIS_SHIFT;
+
+		eu_disable[0] = I915_READ(GEN8_EU_DISABLE0);
+		eu_disable[1] = I915_READ(GEN8_EU_DISABLE1);
+		eu_disable[2] = I915_READ(GEN8_EU_DISABLE2);
+
+		info->slice_total = hweight32(s_enable);
+		/*
+		 * The subslice disable field is global, i.e. it applies
+		 * to each of the enabled slices.
+		*/
+		info->subslice_per_slice = ss_max - hweight32(ss_disable);
+		info->subslice_total = info->slice_total *
+				       info->subslice_per_slice;
+
+		/*
+		 * Iterate through enabled slices and subslices to
+		 * count the total enabled EU.
+		*/
+		for (s = 0; s < s_max; s++) {
+			if (!(s_enable & (0x1 << s)))
+				/* skip disabled slice */
+				continue;
+
+			for (ss = 0; ss < ss_max; ss++) {
+				if (ss_disable & (0x1 << ss))
+					/* skip disabled subslice */
+					continue;
+
+				info->eu_total += eu_max -
+						  hweight8(eu_disable[s] >>
+							   (ss * eu_max));
+			}
+		}
+
+		/*
+		 * SKL is expected to always have a uniform distribution
+		 * of EU across subslices with the exception that any one
+		 * EU in any one subslice may be fused off for die
+		 * recovery.
+		*/
+		info->eu_per_subslice = info->subslice_total ?
+					DIV_ROUND_UP(info->eu_total,
+						     info->subslice_total) : 0;
+		/*
+		 * SKL supports slice power gating on devices with more than
+		 * one slice, and supports EU power gating on devices with
+		 * more than one EU pair per subslice.
+		*/
+		info->has_slice_pg = (info->slice_total > 1) ? 1 : 0;
+		info->has_subslice_pg = 0;
+		info->has_eu_pg = (info->eu_per_subslice > 2) ? 1 : 0;
 	}
+	DRM_DEBUG_DRIVER("slice total: %u\n", info->slice_total);
+	DRM_DEBUG_DRIVER("subslice total: %u\n", info->subslice_total);
+	DRM_DEBUG_DRIVER("subslice per slice: %u\n", info->subslice_per_slice);
+	DRM_DEBUG_DRIVER("EU total: %u\n", info->eu_total);
+	DRM_DEBUG_DRIVER("EU per subslice: %u\n", info->eu_per_subslice);
+	DRM_DEBUG_DRIVER("has slice power gating: %s\n",
+			 info->has_slice_pg ? "y" : "n");
+	DRM_DEBUG_DRIVER("has subslice power gating: %s\n",
+			 info->has_subslice_pg ? "y" : "n");
+	DRM_DEBUG_DRIVER("has EU power gating: %s\n",
+			 info->has_eu_pg ? "y" : "n");
 }
 
 /**