Potential freesync Arithmetic Issue

[Harry Wentland]

Thanks, Bryan, for your report. It was indeed an issue with the merge. 
The fix will be in next week's set of DC patches.

Harry



On 2020-10-28 1:39 p.m., Bryan Angelo wrote:
> While looking at the following commit, I noticed what might be an 
> arithmetic issue potentially stemming from some merge/patch conflict 
> resolution.
> 
> commit ad339f69114a6a145fc94d44376851c53dee3475
> Author: Jaehyun Chung <jaehyun.chung at amd.com <mailto:jaehyun.chung at amd.com>>
> Date:   Thu Jun 18 15:27:35 2020 -0400
> 
>      drm/amd/display: Fix incorrect rounding for 10Hz refresh range
> 
>      [Why]
>      In cases where refresh range is slightly below 10, FreeSync is not
>      active or supported. Need to round values before checking refresh range
>      in order to have FreeSync supported in these cases.
> 
>      [How]
>      Remove redundant values and round values before checking valid 
> refresh range.
> 
>      Signed-off-by: Jaehyun Chung <jaehyun.chung at amd.com 
> <mailto:jaehyun.chung at amd.com>>
>      Reviewed-by: Aric Cyr <Aric.Cyr at amd.com <mailto:Aric.Cyr at amd.com>>
>      Acked-by: Anthony Koo <Anthony.Koo at amd.com 
> <mailto:Anthony.Koo at amd.com>>
>      Acked-by: Eryk Brol <eryk.brol at amd.com <mailto:eryk.brol at amd.com>>
>      Signed-off-by: Alex Deucher <alexander.deucher at amd.com 
> <mailto:alexander.deucher at amd.com>>
> 
> There appears to be an errant plus sign when calculating the 
> refresh_range - 
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/gpu/drm/amd/display/modules/freesync/freesync.c?h=v5.10-rc1#n948 
> <https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgit.kernel.org%2Fpub%2Fscm%2Flinux%2Fkernel%2Fgit%2Ftorvalds%2Flinux.git%2Ftree%2Fdrivers%2Fgpu%2Fdrm%2Famd%2Fdisplay%2Fmodules%2Ffreesync%2Ffreesync.c%3Fh%3Dv5.10-rc1%23n948&data=04%7C01%7CHARRY.WENTLAND%40amd.com%7Cd75a7f7d0f3c41a2079808d87b731dce%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637395082108247063%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C2000&sdata=MBsKCteoT9QgydORyU2e%2FMWyCP0ae0dp8chBzHczbSo%3D&reserved=0>
> 
>    refresh_range = div_u64(in_out_vrr->max_refresh_in_uhz + 500000, 
> 1000000) -
> + div_u64(in_out_vrr->min_refresh_in_uhz + 500000, 1000000);
> 
> I am unfamiliar with the freesync codebase so I opted to present the 
> potential issue here as opposed to preparing a patch.
> 
> Thanks.
> 
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