drm/amd/display: prevent potential division by zero errors

[ Upstream commit 07e388aab042774f284a2ad75a70a194517cdad4 ]

There are two places in apply_below_the_range() where it's possible for
a divide by zero error to occur. So, to fix this make sure the divisor
is non-zero before attempting the computation in both cases.

Cc: stable@vger.kernel.org
Link: https://gitlab.freedesktop.org/drm/amd/-/issues/2637
Fixes: a463b263032f ("drm/amd/display: Fix frames_to_insert math")
Fixes: ded6119e825a ("drm/amd/display: Reinstate LFC optimization")
Reviewed-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Signed-off-by: Hamza Mahfooz <hamza.mahfooz@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/gpu/drm/amd/display/modules/freesync/freesync.c b/drivers/gpu/drm/amd/display/modules/freesync/freesync.c
index 5835b968cac5d36ec6e04847f98d73986145fd91..ed5c9edfdcc566a4b4cb88065d0281976afc0ec5 100644 (file)
--- a/drivers/gpu/drm/amd/display/modules/freesync/freesync.c
+++ b/drivers/gpu/drm/amd/display/modules/freesync/freesync.c
@@ -323,7 +323,9 @@ static void apply_below_the_range(struct core_freesync *core_freesync,
                 *  - Delta for CEIL: delta_from_mid_point_in_us_1
                 *  - Delta for FLOOR: delta_from_mid_point_in_us_2
                 */
-               if ((last_render_time_in_us / mid_point_frames_ceil) < in_out_vrr->min_duration_in_us) {
+               if (mid_point_frames_ceil &&
+                   (last_render_time_in_us / mid_point_frames_ceil) <
+                   in_out_vrr->min_duration_in_us) {
                        /* Check for out of range.
                         * If using CEIL produces a value that is out of range,
                         * then we are forced to use FLOOR.
@@ -370,8 +372,9 @@ 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){
+               if (frames_to_insert &&
+                   (last_render_time_in_us / frames_to_insert) <
+                   in_out_vrr->min_duration_in_us){
                        frames_to_insert -= (frames_to_insert > 1) ?
                                        1 : 0;
                }