drm/i915/dp: Simplify intel_dp_max_data_rate()

Simplify intel_dp_max_data_rate() using
drm_dp_bw_channel_coding_efficiency() to calculate the max data rate for
both DP1.4 and UHBR link rates. This trades a redundant multiply/divide
for readability.

Cc: 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/20231116131841.1588781-11-imre.deak@intel.com

diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
index 7fd883b954a6f3a19b1817aa928b6a903c9234b5..6d5a794b6b7173cee59f63e50a6aa693112aa2de 100644 (file)
--- a/drivers/gpu/drm/i915/display/intel_dp.c
+++ b/drivers/gpu/drm/i915/display/intel_dp.c
@@ -405,29 +405,27 @@ int intel_dp_effective_data_rate(int pixel_clock, int bpp_x16,
 int
 intel_dp_max_data_rate(int max_link_rate, int max_lanes)
 {
-       if (max_link_rate >= 1000000) {
-               /*
-                * UHBR rates always use 128b/132b channel encoding, and have
-                * 97.71% data bandwidth efficiency. Consider max_link_rate the
-                * link bit rate in units of 10000 bps.
-                */
-               int max_link_rate_kbps = max_link_rate * 10;
-
-               max_link_rate_kbps = DIV_ROUND_DOWN_ULL(mul_u32_u32(max_link_rate_kbps, 9671), 10000);
-               max_link_rate = max_link_rate_kbps / 8;
-       }
+       int ch_coding_efficiency =
+               drm_dp_bw_channel_coding_efficiency(drm_dp_is_uhbr_rate(max_link_rate));
+       int max_link_rate_kbps = max_link_rate * 10;
 
+       /*
+        * UHBR rates always use 128b/132b channel encoding, and have
+        * 97.71% data bandwidth efficiency. Consider max_link_rate the
+        * link bit rate in units of 10000 bps.
+        */
        /*
         * Lower than UHBR rates always use 8b/10b channel encoding, and have
         * 80% data bandwidth efficiency for SST non-FEC. However, this turns
-        * out to be a nop by coincidence, and can be skipped:
+        * out to be a nop by coincidence:
         *
         *      int max_link_rate_kbps = max_link_rate * 10;
         *      max_link_rate_kbps = DIV_ROUND_DOWN_ULL(max_link_rate_kbps * 8, 10);
         *      max_link_rate = max_link_rate_kbps / 8;
         */
-
-       return max_link_rate * max_lanes;
+       return DIV_ROUND_DOWN_ULL(mul_u32_u32(max_link_rate_kbps * max_lanes,
+                                             ch_coding_efficiency),
+                                 1000000 * 8);
 }
 
 bool intel_dp_can_bigjoiner(struct intel_dp *intel_dp)