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

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Date:   Mon, 30 Mar 2020 15:16:14 -0700
From:   Nathan Chancellor <natechancellor@...il.com>
To:     Harry Wentland <harry.wentland@....com>,
        Leo Li <sunpeng.li@....com>,
        Alex Deucher <alexander.deucher@....com>,
        Christian König <christian.koenig@....com>,
        "David (ChunMing) Zhou" <David1.Zhou@....com>
Cc:     Rodrigo Siqueira <Rodrigo.Siqueira@....com>,
        amd-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org,
        Nathan Chancellor <natechancellor@...il.com>
Subject: [PATCH] drm/amd/display: Fix 64-bit division error on 32-bit platforms in mod_freesync_build_vrr_params

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@...il.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