drm/i915/tgl: Add DC3CO counter in i915_dmc_info

Adding DC3CO counter in i915_dmc_info debugfs will be
useful for DC3CO validation.
DMC firmware uses DMC_DEBUG3 register as DC3CO counter
register on TGL, as per B.Specs DMC_DEBUG3 is general
purpose register.

v1: comment modification for DMC_DBUG3.
    using GEN >= 12 check instead of IS_TIGERLAKE()
    to print DMC_DEBUG3 counter value.

Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Imre Deak <imre.deak@intel.com>
Cc: Animesh Manna <animesh.manna@intel.com>
Reviewed-by: Imre Deak <imre.deak@intel.com>
Signed-off-by: Anshuman Gupta <anshuman.gupta@intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191003081738.22101-7-anshuman.gupta@intel.com

drivers/gpu/drm/i915/i915_debugfs.c

@@ -2405,6 +2405,13 @@ static int i915_dmc_info(struct seq_file *m, void *unused)
 	if (INTEL_GEN(dev_priv) >= 12) {
 		dc5_reg = TGL_DMC_DEBUG_DC5_COUNT;
 		dc6_reg = TGL_DMC_DEBUG_DC6_COUNT;
+		/*
+		 * NOTE: DMC_DEBUG3 is a general purpose reg.
+		 * According to B.Specs:49196 DMC f/w reuses DC5/6 counter
+		 * reg for DC3CO debugging and validation,
+		 * but TGL DMC f/w is using DMC_DEBUG3 reg for DC3CO counter.
+		 */
+		seq_printf(m, "DC3CO count: %d\n", I915_READ(DMC_DEBUG3));
 	} else {
 		dc5_reg = IS_BROXTON(dev_priv) ? BXT_CSR_DC3_DC5_COUNT :
 						 SKL_CSR_DC3_DC5_COUNT;

drivers/gpu/drm/i915/i915_reg.h

@@ -7268,6 +7268,8 @@ enum {
 #define TGL_DMC_DEBUG_DC5_COUNT	_MMIO(0x101084)
 #define TGL_DMC_DEBUG_DC6_COUNT	_MMIO(0x101088)
 
+#define DMC_DEBUG3		_MMIO(0x101090)
+
 /* interrupts */
 #define DE_MASTER_IRQ_CONTROL   (1 << 31)
 #define DE_SPRITEB_FLIP_DONE    (1 << 29)