drm/i915: extract common link_m_n helpers

Both the dp and fdi code use the exact same computations (ignore minor
differences in conversion between bits and bytes).

This makes it even more apparent that we have a _massive_ mess between
cpu transcoder/fdi link/pch transcoder and pch link settings. And also
that we have hilarious amounts of confusion between edp and dp
(despite that they're identical at a link level).

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

drivers/gpu/drm/i915/i915_drv.h

@@ -107,6 +107,19 @@ struct intel_pch_pll {
 };
 #define I915_NUM_PLLS 2
 
+/* Used by dp and fdi links */
+struct intel_link_m_n {
+	uint32_t	tu;
+	uint32_t	gmch_m;
+	uint32_t	gmch_n;
+	uint32_t	link_m;
+	uint32_t	link_n;
+};
+
+void intel_link_compute_m_n(int bpp, int nlanes,
+			    int pixel_clock, int link_clock,
+			    struct intel_link_m_n *m_n);
+
 struct intel_ddi_plls {
 	int spll_refcount;
 	int wrpll1_refcount;

drivers/gpu/drm/i915/intel_display.c

@@ -3951,37 +3951,27 @@ static int i830_get_display_clock_speed(struct drm_device *dev)
 	return 133000;
 }
 
-struct fdi_m_n {
-	u32        tu;
-	u32        gmch_m;
-	u32        gmch_n;
-	u32        link_m;
-	u32        link_n;
-};
-
 static void
-fdi_reduce_ratio(u32 *num, u32 *den)
+intel_reduce_ratio(uint32_t *num, uint32_t *den)
 {
 	while (*num > 0xffffff || *den > 0xffffff) {
 		*num >>= 1;
 		*den >>= 1;
 	}
 }
 
-static void
-ironlake_compute_m_n(int bits_per_pixel, int nlanes, int pixel_clock,
-		     int link_clock, struct fdi_m_n *m_n)
+void
+intel_link_compute_m_n(int bits_per_pixel, int nlanes,
+		       int pixel_clock, int link_clock,
+		       struct intel_link_m_n *m_n)
 {
-	m_n->tu = 64; /* default size */
-
-	/* BUG_ON(pixel_clock > INT_MAX / 36); */
+	m_n->tu = 64;
 	m_n->gmch_m = bits_per_pixel * pixel_clock;
 	m_n->gmch_n = link_clock * nlanes * 8;
-	fdi_reduce_ratio(&m_n->gmch_m, &m_n->gmch_n);
-
+	intel_reduce_ratio(&m_n->gmch_m, &m_n->gmch_n);
 	m_n->link_m = pixel_clock;
 	m_n->link_n = link_clock;
-	fdi_reduce_ratio(&m_n->link_m, &m_n->link_n);
+	intel_reduce_ratio(&m_n->link_m, &m_n->link_n);
 }
 
 static inline bool intel_panel_use_ssc(struct drm_i915_private *dev_priv)
@@ -5095,7 +5085,7 @@ static void ironlake_set_m_n(struct drm_crtc *crtc,
 	struct intel_crtc *intel_crtc = to_intel_crtc(crtc);
 	enum transcoder cpu_transcoder = intel_crtc->cpu_transcoder;
 	struct intel_encoder *intel_encoder, *edp_encoder = NULL;
-	struct fdi_m_n m_n = {0};
+	struct intel_link_m_n m_n = {0};
 	int target_clock, pixel_multiplier, lane, link_bw;
 	bool is_dp = false, is_cpu_edp = false;
 
@@ -5153,8 +5143,7 @@ static void ironlake_set_m_n(struct drm_crtc *crtc,
 
 	if (pixel_multiplier > 1)
 		link_bw *= pixel_multiplier;
-	ironlake_compute_m_n(intel_crtc->bpp, lane, target_clock, link_bw,
-			     &m_n);
+	intel_link_compute_m_n(intel_crtc->bpp, lane, target_clock, link_bw, &m_n);
 
 	I915_WRITE(PIPE_DATA_M1(cpu_transcoder), TU_SIZE(m_n.tu) | m_n.gmch_m);
 	I915_WRITE(PIPE_DATA_N1(cpu_transcoder), m_n.gmch_n);

drivers/gpu/drm/i915/intel_dp.c

@@ -790,39 +790,6 @@ intel_dp_mode_fixup(struct drm_encoder *encoder,
 	return false;
 }
 
-struct intel_dp_m_n {
-	uint32_t	tu;
-	uint32_t	gmch_m;
-	uint32_t	gmch_n;
-	uint32_t	link_m;
-	uint32_t	link_n;
-};
-
-static void
-intel_reduce_ratio(uint32_t *num, uint32_t *den)
-{
-	while (*num > 0xffffff || *den > 0xffffff) {
-		*num >>= 1;
-		*den >>= 1;
-	}
-}
-
-static void
-intel_dp_compute_m_n(int bpp,
-		     int nlanes,
-		     int pixel_clock,
-		     int link_clock,
-		     struct intel_dp_m_n *m_n)
-{
-	m_n->tu = 64;
-	m_n->gmch_m = (pixel_clock * bpp) >> 3;
-	m_n->gmch_n = link_clock * nlanes;
-	intel_reduce_ratio(&m_n->gmch_m, &m_n->gmch_n);
-	m_n->link_m = pixel_clock;
-	m_n->link_n = link_clock;
-	intel_reduce_ratio(&m_n->link_m, &m_n->link_n);
-}
-
 void
 intel_dp_set_m_n(struct drm_crtc *crtc, struct drm_display_mode *mode,
 		 struct drm_display_mode *adjusted_mode)
@@ -833,7 +800,7 @@ intel_dp_set_m_n(struct drm_crtc *crtc, struct drm_display_mode *mode,
 	struct drm_i915_private *dev_priv = dev->dev_private;
 	struct intel_crtc *intel_crtc = to_intel_crtc(crtc);
 	int lane_count = 4;
-	struct intel_dp_m_n m_n;
+	struct intel_link_m_n m_n;
 	int pipe = intel_crtc->pipe;
 	enum transcoder cpu_transcoder = intel_crtc->cpu_transcoder;
 
@@ -856,8 +823,8 @@ intel_dp_set_m_n(struct drm_crtc *crtc, struct drm_display_mode *mode,
 	 * the number of bytes_per_pixel post-LUT, which we always
 	 * set up for 8-bits of R/G/B, or 3 bytes total.
 	 */
-	intel_dp_compute_m_n(intel_crtc->bpp, lane_count,
-			     mode->clock, adjusted_mode->clock, &m_n);
+	intel_link_compute_m_n(intel_crtc->bpp, lane_count,
+			       mode->clock, adjusted_mode->clock, &m_n);
 
 	if (IS_HASWELL(dev)) {
 		I915_WRITE(PIPE_DATA_M1(cpu_transcoder),