drm/i915/dp: Reuse intel_dp_{max,effective}_data_rate in intel_link_compute_m_n()

Reuse intel_dp_max_data_rate() and intel_dp_effective_data_rate() in
intel_link_compute_m_n(), instead of open-coding the equivalent. Note
the kbit/sec -> kByte/sec unit change in the M/N values, but this not
reducing the precision, as the link rate value is based anyway on a less
precise 10 kbit/sec value.
Suggested-by: Jani Nikula <jani.nikula@linux.intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231116131841.1588781-12-imre.deak@intel.com

drivers/gpu/drm/i915/display/intel_display.c

@@ -2388,36 +2388,17 @@ static void compute_m_n(u32 *ret_m, u32 *ret_n,
 	intel_reduce_m_n_ratio(ret_m, ret_n);
 }
 
-static void
-add_bw_alloc_overhead(int link_clock, int bw_overhead,
-		      int pixel_data_rate, int link_data_rate,
-		      u32 *data_m, u32 *data_n)
-{
-	bool is_uhbr = drm_dp_is_uhbr_rate(link_clock);
-	int ch_coding_efficiency =
-		drm_dp_bw_channel_coding_efficiency(is_uhbr);
-
-	*data_m = DIV_ROUND_UP_ULL(mul_u32_u32(pixel_data_rate, bw_overhead),
-				   1000000);
-	*data_n = DIV_ROUND_DOWN_ULL(mul_u32_u32(link_data_rate, ch_coding_efficiency),
-				     1000000);
-}
-
 void
 intel_link_compute_m_n(u16 bits_per_pixel_x16, int nlanes,
 		       int pixel_clock, int link_clock,
 		       int bw_overhead,
 		       struct intel_link_m_n *m_n)
 {
-	u32 data_clock = DIV_ROUND_UP(bits_per_pixel_x16 * pixel_clock, 16);
 	u32 link_symbol_clock = intel_dp_link_symbol_clock(link_clock);
-	u32 data_m;
-	u32 data_n;
+	u32 data_m = intel_dp_effective_data_rate(pixel_clock, bits_per_pixel_x16,
+						  bw_overhead);
+	u32 data_n = intel_dp_max_data_rate(link_clock, nlanes);
 
-	add_bw_alloc_overhead(link_clock, bw_overhead,
-			      data_clock,
-			      link_clock * 10 * nlanes,
-			      &data_m, &data_n);
 	/*
 	 * Windows/BIOS uses fixed M/N values always. Follow suit.
 	 *