drm/dp_mst: Add PBN calculation for DSC modes

[linux.git] / drivers / gpu / drm / drm_dp_mst_topology.c

diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
index e68d23043973ccd7fe3dd51f15b53cdd70e7face..2443532341d00209182e361b264da00aac8b3418 100644 (file)
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -4415,10 +4415,11 @@ EXPORT_SYMBOL(drm_dp_check_act_status);
  * drm_dp_calc_pbn_mode() - Calculate the PBN for a mode.
  * @clock: dot clock for the mode
  * @bpp: bpp for the mode.
+ * @dsc: DSC mode. If true, bpp has units of 1/16 of a bit per pixel
  *
  * This uses the formula in the spec to calculate the PBN value for a mode.
  */
-int drm_dp_calc_pbn_mode(int clock, int bpp)
+int drm_dp_calc_pbn_mode(int clock, int bpp, bool dsc)
 {
        /*
         * margin 5300ppm + 300ppm ~ 0.6% as per spec, factor is 1.006
@@ -4429,7 +4430,16 @@ int drm_dp_calc_pbn_mode(int clock, int bpp)
         * peak_kbps *= (1006/1000)
         * peak_kbps *= (64/54)
         * peak_kbps *= 8    convert to bytes
+        *
+        * If the bpp is in units of 1/16, further divide by 16. Put this
+        * factor in the numerator rather than the denominator to avoid
+        * integer overflow
         */
+
+       if (dsc)
+               return DIV_ROUND_UP_ULL(mul_u32_u32(clock * (bpp / 16), 64 * 1006),
+                                       8 * 54 * 1000 * 1000);
+
        return DIV_ROUND_UP_ULL(mul_u32_u32(clock * bpp, 64 * 1006),
                                8 * 54 * 1000 * 1000);
 }