drm/i915: Detect eDRAM with the enabled bit only

At the moment we compare the whole EDRAM_PRESENT/EDRAMCAP register value
to 1 while EDRAM_PRESENT is only bit 0 (the rest may be used to describe
eDRAM capabilities).

To be more future proof, only look at bit 0 to detect eDRAM presence.

Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>
Reviewed-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_reg.h

@@ -5994,6 +5994,7 @@ enum skl_disp_power_wells {
 #define  HSW_IDICR				0x9008
 #define    IDIHASHMSK(x)			(((x) & 0x3f) << 16)
 #define  HSW_EDRAM_PRESENT			0x120010
+#define    EDRAM_ENABLED			0x1
 
 #define GEN6_UCGCTL1				0x9400
 # define GEN6_EU_TCUNIT_CLOCK_GATE_DISABLE		(1 << 16)

drivers/gpu/drm/i915/intel_uncore.c

@@ -329,7 +329,7 @@ static void intel_uncore_ellc_detect(struct drm_device *dev)
 	struct drm_i915_private *dev_priv = dev->dev_private;
 
 	if ((IS_HASWELL(dev) || IS_BROADWELL(dev)) &&
-	    (__raw_i915_read32(dev_priv, HSW_EDRAM_PRESENT) == 1)) {
+	    (__raw_i915_read32(dev_priv, HSW_EDRAM_PRESENT) & EDRAM_ENABLED)) {
 		/* The docs do not explain exactly how the calculation can be
 		 * made. It is somewhat guessable, but for now, it's always
 		 * 128MB.