drm/i915: Fix the g4x watermark TLB miss workaround

The g4x watermark TLB miss workaround requires that we bump up the
watermark by the difference between 8 full lines and the FIFO size.
Unfortunately the way we compute it at the moment ignores the size
of the pixels. The code also used the primary plane width as the
cursor width when computing the TLB miss w/a for the cursor.
Let's fix both problems.
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170421181432.15216-9-ville.syrjala@linux.intel.comReviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>

drivers/gpu/drm/i915/intel_pm.c

@@ -811,7 +811,7 @@ static bool g4x_compute_wm0(struct drm_i915_private *dev_priv,
 	struct intel_crtc *crtc;
 	const struct drm_display_mode *adjusted_mode;
 	const struct drm_framebuffer *fb;
-	int htotal, hdisplay, clock, cpp;
+	int htotal, plane_width, cursor_width, clock, cpp;
 	int line_time_us, line_count;
 	int entries, tlb_miss;
 
@@ -826,12 +826,13 @@ static bool g4x_compute_wm0(struct drm_i915_private *dev_priv,
 	fb = crtc->base.primary->state->fb;
 	clock = adjusted_mode->crtc_clock;
 	htotal = adjusted_mode->crtc_htotal;
-	hdisplay = crtc->config->pipe_src_w;
+	plane_width = crtc->config->pipe_src_w;
+	cursor_width = crtc->base.cursor->state->crtc_w;
 	cpp = fb->format->cpp[0];
 
 	/* Use the small buffer method to calculate plane watermark */
 	entries = ((clock * cpp / 1000) * display_latency_ns) / 1000;
-	tlb_miss = display->fifo_size*display->cacheline_size - hdisplay * 8;
+	tlb_miss = display->fifo_size*display->cacheline_size - plane_width * cpp * 8;
 	if (tlb_miss > 0)
 		entries += tlb_miss;
 	entries = DIV_ROUND_UP(entries, display->cacheline_size);
@@ -842,8 +843,8 @@ static bool g4x_compute_wm0(struct drm_i915_private *dev_priv,
 	/* Use the large buffer method to calculate cursor watermark */
 	line_time_us = max(htotal * 1000 / clock, 1);
 	line_count = (cursor_latency_ns / line_time_us + 1000) / 1000;
-	entries = line_count * crtc->base.cursor->state->crtc_w * 4;
-	tlb_miss = cursor->fifo_size*cursor->cacheline_size - hdisplay * 8;
+	entries = line_count * cursor_width * 4;
+	tlb_miss = cursor->fifo_size*cursor->cacheline_size - cursor_width * 4 * 8;
 	if (tlb_miss > 0)
 		entries += tlb_miss;
 	entries = DIV_ROUND_UP(entries, cursor->cacheline_size);