drm/amd/display: LFC not working on 2.0x range monitors (v2)

[Why]
Nominal pixel clock and EDID information differ in precision so although
monitor reports maximum refresh is 2x minimum, LFC was not being
enabled.

[How]
Use minimum refresh rate as nominal/2 when EDID dictates that min
refresh = max refresh/2.

v2: squash in 64 bit divide fix

Signed-off-by: Aric Cyr <aric.cyr@amd.com>
Reviewed-by: Nicholas Kazlauskas <Nicholas.Kazlauskas@amd.com>
Acked-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

diff --git a/drivers/gpu/drm/amd/display/modules/freesync/freesync.c b/drivers/gpu/drm/amd/display/modules/freesync/freesync.c
index 4e54282..c33454a 100644 (file)
--- a/drivers/gpu/drm/amd/display/modules/freesync/freesync.c
+++ b/drivers/gpu/drm/amd/display/modules/freesync/freesync.c
@@ -734,6 +734,7 @@ void mod_freesync_build_vrr_params(struct mod_freesync *mod_freesync,
 {
        struct core_freesync *core_freesync = NULL;
        unsigned long long nominal_field_rate_in_uhz = 0;
+       unsigned long long rounded_nominal_in_uhz = 0;
        unsigned int refresh_range = 0;
        unsigned long long min_refresh_in_uhz = 0;
        unsigned long long max_refresh_in_uhz = 0;
@@ -750,17 +751,20 @@ void mod_freesync_build_vrr_params(struct mod_freesync *mod_freesync,
        min_refresh_in_uhz = in_config->min_refresh_in_uhz;
        max_refresh_in_uhz = in_config->max_refresh_in_uhz;
 
-       // Don't allow min > max
-       if (min_refresh_in_uhz > max_refresh_in_uhz)
-               min_refresh_in_uhz = max_refresh_in_uhz;
-
        // Full range may be larger than current video timing, so cap at nominal
        if (max_refresh_in_uhz > nominal_field_rate_in_uhz)
                max_refresh_in_uhz = nominal_field_rate_in_uhz;
 
        // Full range may be larger than current video timing, so cap at nominal
-       if (min_refresh_in_uhz > nominal_field_rate_in_uhz)
-               min_refresh_in_uhz = nominal_field_rate_in_uhz;
+       if (min_refresh_in_uhz > max_refresh_in_uhz)
+               min_refresh_in_uhz = max_refresh_in_uhz;
+
+       // If a monitor reports exactly max refresh of 2x of min, enforce it on nominal
+       rounded_nominal_in_uhz =
+                       div_u64(nominal_field_rate_in_uhz + 50000, 100000) * 100000;
+       if (in_config->max_refresh_in_uhz == (2 * in_config->min_refresh_in_uhz) &&
+               in_config->max_refresh_in_uhz == rounded_nominal_in_uhz)
+               min_refresh_in_uhz = div_u64(nominal_field_rate_in_uhz, 2);
 
        if (!vrr_settings_require_update(core_freesync,
                        in_config, (unsigned int)min_refresh_in_uhz, (unsigned int)max_refresh_in_uhz,
@@ -792,11 +796,6 @@ void mod_freesync_build_vrr_params(struct mod_freesync *mod_freesync,
                refresh_range = in_out_vrr->max_refresh_in_uhz -
                                in_out_vrr->min_refresh_in_uhz;
 
-               in_out_vrr->btr.margin_in_us = in_out_vrr->max_duration_in_us -
-                               2 * in_out_vrr->min_duration_in_us;
-               if (in_out_vrr->btr.margin_in_us > BTR_MAX_MARGIN)
-                       in_out_vrr->btr.margin_in_us = BTR_MAX_MARGIN;
-
                in_out_vrr->supported = true;
        }
 
@@ -804,9 +803,14 @@ void mod_freesync_build_vrr_params(struct mod_freesync *mod_freesync,
 
        in_out_vrr->btr.btr_enabled = in_config->btr;
 
-       if (in_out_vrr->max_refresh_in_uhz <
-                       2 * in_out_vrr->min_refresh_in_uhz)
+       if (in_out_vrr->max_refresh_in_uhz < (2 * in_out_vrr->min_refresh_in_uhz))
                in_out_vrr->btr.btr_enabled = false;
+       else {
+               in_out_vrr->btr.margin_in_us = in_out_vrr->max_duration_in_us -
+                               2 * in_out_vrr->min_duration_in_us;
+               if (in_out_vrr->btr.margin_in_us > BTR_MAX_MARGIN)
+                       in_out_vrr->btr.margin_in_us = BTR_MAX_MARGIN;
+       }
 
        in_out_vrr->btr.btr_active = false;
        in_out_vrr->btr.inserted_duration_in_us = 0;
@@ -1008,8 +1012,8 @@ unsigned long long mod_freesync_calc_nominal_field_rate(
        unsigned int total = stream->timing.h_total * stream->timing.v_total;
 
        /* Calculate nominal field rate for stream, rounded up to nearest integer */
-       nominal_field_rate_in_uhz = stream->timing.pix_clk_100hz / 10;
-       nominal_field_rate_in_uhz *= 1000ULL * 1000ULL * 1000ULL;
+       nominal_field_rate_in_uhz = stream->timing.pix_clk_100hz;
+       nominal_field_rate_in_uhz *= 100000000ULL;
 
        nominal_field_rate_in_uhz =     div_u64(nominal_field_rate_in_uhz, total);