[PATCH 5.10 377/406] drm/amd/display: prevent potential division by zero errors

Greg Kroah-Hartman
2023-09-17T19:41:48Z

From: Hamza Mahfooz <hamza.mahfooz@amd.com>

commit 07e388aab042774f284a2ad75a70a194517cdad4 upstream.

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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/gpu/drm/amd/display/modules/freesync/freesync.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)

--- a/drivers/gpu/drm/amd/display/modules/freesync/freesync.c
+++ b/drivers/gpu/drm/amd/display/modules/freesync/freesync.c
@@ -327,7 +327,9 @@ static void apply_below_the_range(struct
* - 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.
@@ -374,8 +376,9 @@ static void apply_below_the_range(struct
/* 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;
}