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SubjectRe: [PATCH] drm/amd/display: prevent potential division by zero errors
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On 2023-09-05 14:53, Hamza Mahfooz wrote:
> 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")
> Signed-off-by: Hamza Mahfooz <hamza.mahfooz@amd.com>
> ---
> drivers/gpu/drm/amd/display/modules/freesync/freesync.c | 9 ++++++---
> 1 file changed, 6 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/display/modules/freesync/freesync.c b/drivers/gpu/drm/amd/display/modules/freesync/freesync.c
> index dbd60811f95d..ef3a67409021 100644
> --- a/drivers/gpu/drm/amd/display/modules/freesync/freesync.c
> +++ b/drivers/gpu/drm/amd/display/modules/freesync/freesync.c
> @@ -338,7 +338,9 @@ 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.
> @@ -385,8 +387,9 @@ 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;
> }


Reviewed-by: Aurabindo Pillai <aurabindo.pillai@amd.com>

--

Thanks & Regards,
Jay

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