drm/amd/display: Fix frames_to_insert math

[Why]
The math on deciding on how many
"frames to insert" sometimes sent us over the max refresh rate.
Also integer overflow can occur if we have high refresh rates.

[How]
Instead of clipping the  frame duration such that it doesn’t go below the min,
just remove a frame from the number of frames to insert. +
Use unsigned long long for intermediate calculations to prevent
integer overflow.

Signed-off-by: Bayan Zabihiyan <bayan.zabihiyan@amd.com>
Reviewed-by: Aric Cyr <Aric.Cyr@amd.com>
Acked-by: Leo Li <sunpeng.li@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 7c20171..a53666f 100644 (file)
--- a/drivers/gpu/drm/amd/display/modules/freesync/freesync.c
+++ b/drivers/gpu/drm/amd/display/modules/freesync/freesync.c
@@ -435,6 +435,12 @@ static void apply_below_the_range(struct core_freesync *core_freesync,
                /* Either we've calculated the number of frames to insert,
                 * or we need to insert min duration frames
                 */
+               if (last_render_time_in_us / frames_to_insert <
+                               in_out_vrr->min_duration_in_us){
+                       frames_to_insert -= (frames_to_insert > 1) ?
+                                       1 : 0;
+               }
+
                if (frames_to_insert > 0)
                        inserted_frame_duration_in_us = last_render_time_in_us /
                                                        frames_to_insert;
@@ -887,8 +893,8 @@ 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 int refresh_range = 0;
-       unsigned int min_refresh_in_uhz = 0;
-       unsigned int max_refresh_in_uhz = 0;
+       unsigned long long min_refresh_in_uhz = 0;
+       unsigned long long max_refresh_in_uhz = 0;
 
        if (mod_freesync == NULL)
                return;
@@ -915,7 +921,7 @@ void mod_freesync_build_vrr_params(struct mod_freesync *mod_freesync,
                min_refresh_in_uhz = nominal_field_rate_in_uhz;
 
        if (!vrr_settings_require_update(core_freesync,
-                       in_config, min_refresh_in_uhz, max_refresh_in_uhz,
+                       in_config, (unsigned int)min_refresh_in_uhz, (unsigned int)max_refresh_in_uhz,
                        in_out_vrr))
                return;
 
@@ -931,15 +937,15 @@ void mod_freesync_build_vrr_params(struct mod_freesync *mod_freesync,
                return;
 
        } else {
-               in_out_vrr->min_refresh_in_uhz = min_refresh_in_uhz;
+               in_out_vrr->min_refresh_in_uhz = (unsigned int)min_refresh_in_uhz;
                in_out_vrr->max_duration_in_us =
                                calc_duration_in_us_from_refresh_in_uhz(
-                                               min_refresh_in_uhz);
+                                               (unsigned int)min_refresh_in_uhz);
 
-               in_out_vrr->max_refresh_in_uhz = max_refresh_in_uhz;
+               in_out_vrr->max_refresh_in_uhz = (unsigned int)max_refresh_in_uhz;
                in_out_vrr->min_duration_in_us =
                                calc_duration_in_us_from_refresh_in_uhz(
-                                               max_refresh_in_uhz);
+                                               (unsigned int)max_refresh_in_uhz);
 
                refresh_range = in_out_vrr->max_refresh_in_uhz -
                                in_out_vrr->min_refresh_in_uhz;
@@ -950,17 +956,18 @@ void mod_freesync_build_vrr_params(struct mod_freesync *mod_freesync,
        in_out_vrr->fixed.ramping_active = in_config->ramping;
 
        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)
                in_out_vrr->btr.btr_enabled = false;
+
        in_out_vrr->btr.btr_active = false;
        in_out_vrr->btr.inserted_duration_in_us = 0;
        in_out_vrr->btr.frames_to_insert = 0;
        in_out_vrr->btr.frame_counter = 0;
        in_out_vrr->btr.mid_point_in_us =
-                       in_out_vrr->min_duration_in_us +
-                               (in_out_vrr->max_duration_in_us -
-                               in_out_vrr->min_duration_in_us) / 2;
+                               (in_out_vrr->min_duration_in_us +
+                                in_out_vrr->max_duration_in_us) / 2;
 
        if (in_out_vrr->state == VRR_STATE_UNSUPPORTED) {
                in_out_vrr->adjust.v_total_min = stream->timing.v_total;