drm/i915/skl/kbl: Add support for pipe fusing

On SKL and KBL we can have pipe A/B/C disabled by fuse settings. The
pipes must be fused in descending order (e.g. C, B+C, A+B+C). We simply
decrease info->num_pipes if we find a valid fused out config.

v2: Don't store the pipe disabled mask in device info (Damien)

v3: Don't check FUSE_STRAP register for pipe c disabled

Cc: Damien Lespiau <damien.lespiau@intel.com>
Signed-off-by: Patrik Jakobsson <patrik.jakobsson@linux.intel.com>
Reviewed-by: Damien Lespiau <damien.lespiau@intel.com>
[Jani: fixed some checkpatch indentation complaints]
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1453300280-10661-1-git-send-email-patrik.jakobsson@linux.intel.com

drivers/gpu/drm/i915/i915_dma.c

@@ -809,6 +809,37 @@ static void intel_device_info_runtime_init(struct drm_device *dev)
 			DRM_INFO("Display fused off, disabling\n");
 			info->num_pipes = 0;
 		}
+	} else if (info->num_pipes > 0 && INTEL_INFO(dev)->gen == 9) {
+		u32 dfsm = I915_READ(SKL_DFSM);
+		u8 disabled_mask = 0;
+		bool invalid;
+		int num_bits;
+
+		if (dfsm & SKL_DFSM_PIPE_A_DISABLE)
+			disabled_mask |= BIT(PIPE_A);
+		if (dfsm & SKL_DFSM_PIPE_B_DISABLE)
+			disabled_mask |= BIT(PIPE_B);
+		if (dfsm & SKL_DFSM_PIPE_C_DISABLE)
+			disabled_mask |= BIT(PIPE_C);
+
+		num_bits = hweight8(disabled_mask);
+
+		switch (disabled_mask) {
+		case BIT(PIPE_A):
+		case BIT(PIPE_B):
+		case BIT(PIPE_A) | BIT(PIPE_B):
+		case BIT(PIPE_A) | BIT(PIPE_C):
+			invalid = true;
+			break;
+		default:
+			invalid = false;
+		}
+
+		if (num_bits > info->num_pipes || invalid)
+			DRM_ERROR("invalid pipe fuse configuration: 0x%x\n",
+				  disabled_mask);
+		else
+			info->num_pipes -= num_bits;
 	}
 
 	/* Initialize slice/subslice/EU info */

drivers/gpu/drm/i915/i915_reg.h

@@ -5994,6 +5994,9 @@ enum skl_disp_power_wells {
 #define SKL_DFSM_CDCLK_LIMIT_540	(1 << 23)
 #define SKL_DFSM_CDCLK_LIMIT_450	(2 << 23)
 #define SKL_DFSM_CDCLK_LIMIT_337_5	(3 << 23)
+#define SKL_DFSM_PIPE_A_DISABLE		(1 << 30)
+#define SKL_DFSM_PIPE_B_DISABLE		(1 << 21)
+#define SKL_DFSM_PIPE_C_DISABLE		(1 << 28)
 
 #define GEN7_FF_SLICE_CS_CHICKEN1	_MMIO(0x20e0)
 #define   GEN9_FFSC_PERCTX_PREEMPT_CTRL	(1<<14)