drm/i915: Don't multiply the watermark latency values too early

The LP1+ watermark latency values need to be multiplied by 5 to
make them suitable for watermark calculations. However on pre-HSW
platforms we're going to need the raw value later when we have to
write it to the WM_LPn registers' latency field. So delay the
multiplication until it's needed.

Note: Paulo complains that the units of wm (now in 100ns) aren't
really clear and I agree. But that can be fixed later on ...

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
[danvet: Add a comment about the unit obfuscation.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_pm.c

@@ -2361,10 +2361,10 @@ static void intel_read_wm_latency(struct drm_device *dev, uint16_t wm[5])
 		wm[0] = (sskpd >> 56) & 0xFF;
 		if (wm[0] == 0)
 			wm[0] = sskpd & 0xF;
-		wm[1] = ((sskpd >> 4) & 0xFF) * 5;
-		wm[2] = ((sskpd >> 12) & 0xFF) * 5;
-		wm[3] = ((sskpd >> 20) & 0x1FF) * 5;
-		wm[4] = ((sskpd >> 32) & 0x1FF) * 5;
+		wm[1] = (sskpd >> 4) & 0xFF;
+		wm[2] = (sskpd >> 12) & 0xFF;
+		wm[3] = (sskpd >> 20) & 0x1FF;
+		wm[4] = (sskpd >> 32) & 0x1FF;
 	}
 }
 
@@ -2442,7 +2442,7 @@ static void hsw_compute_wm_results(struct drm_device *dev,
 	int level, max_level, wm_lp;
 
 	for (level = 1; level <= 4; level++)
-		if (!hsw_compute_lp_wm(wm[level], lp_maximums, params,
+		if (!hsw_compute_lp_wm(wm[level] * 5, lp_maximums, params,
 				       &lp_results[level - 1]))
 			break;
 	max_level = level - 1;