[PATCH] drm/amd/display: Fix 64-bit division error on 32-bit platforms in mod_freesync_build_vrr_params

[PATCH] drm/amd/display: Fix 64-bit division error on 32-bit platforms in mod_freesync_build_vrr_params

[Nathan Chancellor]

When building arm32 allyesconfig,

ld.lld: error: undefined symbol: __aeabi_uldivmod
>>> referenced by freesync.c
>>>               gpu/drm/amd/display/modules/freesync/freesync.o:(mod_freesync_build_vrr_params) in archive drivers/built-in.a
>>> did you mean: __aeabi_uidivmod
>>> defined in: arch/arm/lib/lib.a(lib1funcs.o)

Use div_u64 in the two locations that do 64-bit divisior, which both
have a u64 dividend and u32 divisor.

Fixes: 349a370781de ("drm/amd/display: LFC not working on 2.0x range monitors")
Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
---
 drivers/gpu/drm/amd/display/modules/freesync/freesync.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/modules/freesync/freesync.c b/drivers/gpu/drm/amd/display/modules/freesync/freesync.c
index 8911f01671aa..c33454a9e0b4 100644
--- a/drivers/gpu/drm/amd/display/modules/freesync/freesync.c
+++ b/drivers/gpu/drm/amd/display/modules/freesync/freesync.c
@@ -761,10 +761,10 @@ void mod_freesync_build_vrr_params(struct mod_freesync *mod_freesync,
 
 	// If a monitor reports exactly max refresh of 2x of min, enforce it on nominal
 	rounded_nominal_in_uhz =
-			((nominal_field_rate_in_uhz + 50000) / 100000) * 100000;
+			div_u64(nominal_field_rate_in_uhz + 50000, 100000) * 100000;
 	if (in_config->max_refresh_in_uhz == (2 * in_config->min_refresh_in_uhz) &&
 		in_config->max_refresh_in_uhz == rounded_nominal_in_uhz)
-		min_refresh_in_uhz = nominal_field_rate_in_uhz / 2;
+		min_refresh_in_uhz = div_u64(nominal_field_rate_in_uhz, 2);
 
 	if (!vrr_settings_require_update(core_freesync,
 			in_config, (unsigned int)min_refresh_in_uhz, (unsigned int)max_refresh_in_uhz,
-- 
2.26.0

Re: [PATCH] drm/amd/display: Fix 64-bit division error on 32-bit platforms in mod_freesync_build_vrr_params

[Alex Deucher]

On Tue, Mar 31, 2020 at 3:38 AM Nathan Chancellor
<natechancellor@gmail.com> wrote:
>
> When building arm32 allyesconfig,
>
> ld.lld: error: undefined symbol: __aeabi_uldivmod
> >>> referenced by freesync.c
> >>>               gpu/drm/amd/display/modules/freesync/freesync.o:(mod_freesync_build_vrr_params) in archive drivers/built-in.a
> >>> did you mean: __aeabi_uidivmod
> >>> defined in: arch/arm/lib/lib.a(lib1funcs.o)
>
> Use div_u64 in the two locations that do 64-bit divisior, which both
> have a u64 dividend and u32 divisor.
>
> Fixes: 349a370781de ("drm/amd/display: LFC not working on 2.0x range monitors")
> Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>

Applied.  Thanks!

Alex

> ---
>  drivers/gpu/drm/amd/display/modules/freesync/freesync.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/display/modules/freesync/freesync.c b/drivers/gpu/drm/amd/display/modules/freesync/freesync.c
> index 8911f01671aa..c33454a9e0b4 100644
> --- a/drivers/gpu/drm/amd/display/modules/freesync/freesync.c
> +++ b/drivers/gpu/drm/amd/display/modules/freesync/freesync.c
> @@ -761,10 +761,10 @@ void mod_freesync_build_vrr_params(struct mod_freesync *mod_freesync,
>
>         // If a monitor reports exactly max refresh of 2x of min, enforce it on nominal
>         rounded_nominal_in_uhz =
> -                       ((nominal_field_rate_in_uhz + 50000) / 100000) * 100000;
> +                       div_u64(nominal_field_rate_in_uhz + 50000, 100000) * 100000;
>         if (in_config->max_refresh_in_uhz == (2 * in_config->min_refresh_in_uhz) &&
>                 in_config->max_refresh_in_uhz == rounded_nominal_in_uhz)
> -               min_refresh_in_uhz = nominal_field_rate_in_uhz / 2;
> +               min_refresh_in_uhz = div_u64(nominal_field_rate_in_uhz, 2);
>
>         if (!vrr_settings_require_update(core_freesync,
>                         in_config, (unsigned int)min_refresh_in_uhz, (unsigned int)max_refresh_in_uhz,
> --
> 2.26.0
>
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