drm/i915/dp: Report a rounded-down value as the maximum data rate

Callers of intel_dp_max_data_rate() use the return value as an upper
bound for the BW a given mode requires. As such the rounding shouldn't
result in a bigger value than the actual upper bound. Use round-down
instead of -closest accordingly.

Cc: Jani Nikula <jani.nikula@linux.intel.com>
Reviewed-by: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231116131841.1588781-10-imre.deak@intel.com

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

@@ -413,7 +413,7 @@ intel_dp_max_data_rate(int max_link_rate, int max_lanes)
 		 */
 		int max_link_rate_kbps = max_link_rate * 10;
 
-		max_link_rate_kbps = DIV_ROUND_CLOSEST_ULL(mul_u32_u32(max_link_rate_kbps, 9671), 10000);
+		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;
 	}
 
@@ -423,7 +423,7 @@ intel_dp_max_data_rate(int max_link_rate, int max_lanes)
 	 * out to be a nop by coincidence, and can be skipped:
 	 *
 	 *	int max_link_rate_kbps = max_link_rate * 10;
-	 *	max_link_rate_kbps = DIV_ROUND_CLOSEST_ULL(max_link_rate_kbps * 8, 10);
+	 *	max_link_rate_kbps = DIV_ROUND_DOWN_ULL(max_link_rate_kbps * 8, 10);
 	 *	max_link_rate = max_link_rate_kbps / 8;
 	 */