* [PATCH] drm/radeon/rs780: prevent division by zero in refresh rate calculation
@ 2026-04-28 19:03 Evgenii Burenchev
2026-04-29 19:04 ` kernel test robot
2026-04-29 21:46 ` kernel test robot
0 siblings, 2 replies; 4+ messages in thread
From: Evgenii Burenchev @ 2026-04-28 19:03 UTC (permalink / raw)
To: stable, Greg Kroah-Hartman
Cc: Evgenii Burenchev, alexander.deucher, christian.koenig, airlied,
simona, amd-gfx, dri-devel, linux-kernel
drm_mode_vrefresh() may return zero when mode clock is zero even if
htotal and vtotal are non-zero. Current code checks only htotal and
vtotal, allowing refresh_rate to become zero and subsequently causing
division by zero in rs780_program_at().
Fix by adding mode clock validation and fallback to default 60Hz in
rs780_get_pm_mode_parameters(). Add WARN_ON in rs780_program_at() to
catch such cases during development, ensuring safe fallback in all
scenarios.
Found by Linux Verification Center (linuxtesting.org) with SVACE.
Signed-off-by: Evgenii Burenchev <evg28bur@yandex.ru>
---
drivers/gpu/drm/radeon/rs780_dpm.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/drivers/gpu/drm/radeon/rs780_dpm.c b/drivers/gpu/drm/radeon/rs780_dpm.c
index 64bb4cafb8b5..fe45b7dac9f4 100644
--- a/drivers/gpu/drm/radeon/rs780_dpm.c
+++ b/drivers/gpu/drm/radeon/rs780_dpm.c
@@ -65,6 +65,8 @@ static void rs780_get_pm_mode_parameters(struct radeon_device *rdev)
pi->crtc_id = radeon_crtc->crtc_id;
if (crtc->mode.htotal && crtc->mode.vtotal)
pi->refresh_rate = drm_mode_vrefresh(&crtc->mode);
+ if (pi->refresh_rate == 0)
+ pi->refresh_rate = 60;
break;
}
}
@@ -363,6 +365,8 @@ static void rs780_program_at(struct radeon_device *rdev)
{
struct igp_power_info *pi = rs780_get_pi(rdev);
+ WARN_ON(pi->refresh_rate == 0);
+
WREG32(FVTHROT_TARGET_REG, 30000000 / pi->refresh_rate);
WREG32(FVTHROT_CB1, 1000000 * 5 / pi->refresh_rate);
WREG32(FVTHROT_CB2, 1000000 * 10 / pi->refresh_rate);
--
2.43.0
^ permalink raw reply related [flat|nested] 4+ messages in thread* Re: [PATCH] drm/radeon/rs780: prevent division by zero in refresh rate calculation
2026-04-28 19:03 [PATCH] drm/radeon/rs780: prevent division by zero in refresh rate calculation Evgenii Burenchev
@ 2026-04-29 19:04 ` kernel test robot
2026-04-29 21:46 ` kernel test robot
1 sibling, 0 replies; 4+ messages in thread
From: kernel test robot @ 2026-04-29 19:04 UTC (permalink / raw)
To: Evgenii Burenchev, stable, Greg Kroah-Hartman
Cc: oe-kbuild-all, Evgenii Burenchev, alexander.deucher,
christian.koenig, airlied, simona, amd-gfx, dri-devel,
linux-kernel
Hi Evgenii,
kernel test robot noticed the following build warnings:
[auto build test WARNING on drm-misc/drm-misc-next]
[also build test WARNING on linus/master v7.1-rc1 next-20260428]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]
url: https://github.com/intel-lab-lkp/linux/commits/Evgenii-Burenchev/drm-radeon-rs780-prevent-division-by-zero-in-refresh-rate-calculation/20260429-055830
base: https://gitlab.freedesktop.org/drm/misc/kernel.git drm-misc-next
patch link: https://lore.kernel.org/r/20260428190318.34413-1-evg28bur%40yandex.ru
patch subject: [PATCH] drm/radeon/rs780: prevent division by zero in refresh rate calculation
config: parisc-defconfig (https://download.01.org/0day-ci/archive/20260430/202604300247.Gzeia1bh-lkp@intel.com/config)
compiler: hppa-linux-gcc (GCC) 15.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260430/202604300247.Gzeia1bh-lkp@intel.com/reproduce)
If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202604300247.Gzeia1bh-lkp@intel.com/
All warnings (new ones prefixed by >>):
drivers/gpu/drm/radeon/rs780_dpm.c: In function 'rs780_get_pm_mode_parameters':
>> drivers/gpu/drm/radeon/rs780_dpm.c:66:25: warning: this 'if' clause does not guard... [-Wmisleading-indentation]
66 | if (crtc->mode.htotal && crtc->mode.vtotal)
| ^~
drivers/gpu/drm/radeon/rs780_dpm.c:68:33: note: ...this statement, but the latter is misleadingly indented as if it were guarded by the 'if'
68 | if (pi->refresh_rate == 0)
| ^~
vim +/if +66 drivers/gpu/drm/radeon/rs780_dpm.c
9d67006e6ebc6c Alex Deucher 2013-04-12 48
9d67006e6ebc6c Alex Deucher 2013-04-12 49 static void rs780_get_pm_mode_parameters(struct radeon_device *rdev)
9d67006e6ebc6c Alex Deucher 2013-04-12 50 {
9d67006e6ebc6c Alex Deucher 2013-04-12 51 struct igp_power_info *pi = rs780_get_pi(rdev);
9d67006e6ebc6c Alex Deucher 2013-04-12 52 struct radeon_mode_info *minfo = &rdev->mode_info;
9d67006e6ebc6c Alex Deucher 2013-04-12 53 struct drm_crtc *crtc;
9d67006e6ebc6c Alex Deucher 2013-04-12 54 struct radeon_crtc *radeon_crtc;
9d67006e6ebc6c Alex Deucher 2013-04-12 55 int i;
9d67006e6ebc6c Alex Deucher 2013-04-12 56
9d67006e6ebc6c Alex Deucher 2013-04-12 57 /* defaults */
9d67006e6ebc6c Alex Deucher 2013-04-12 58 pi->crtc_id = 0;
9d67006e6ebc6c Alex Deucher 2013-04-12 59 pi->refresh_rate = 60;
9d67006e6ebc6c Alex Deucher 2013-04-12 60
9d67006e6ebc6c Alex Deucher 2013-04-12 61 for (i = 0; i < rdev->num_crtc; i++) {
9d67006e6ebc6c Alex Deucher 2013-04-12 62 crtc = (struct drm_crtc *)minfo->crtcs[i];
9d67006e6ebc6c Alex Deucher 2013-04-12 63 if (crtc && crtc->enabled) {
9d67006e6ebc6c Alex Deucher 2013-04-12 64 radeon_crtc = to_radeon_crtc(crtc);
9d67006e6ebc6c Alex Deucher 2013-04-12 65 pi->crtc_id = radeon_crtc->crtc_id;
9d67006e6ebc6c Alex Deucher 2013-04-12 @66 if (crtc->mode.htotal && crtc->mode.vtotal)
c3eaa088277709 Alex Deucher 2013-09-13 67 pi->refresh_rate = drm_mode_vrefresh(&crtc->mode);
0d99a77de43b3f Evgenii Burenchev 2026-04-28 68 if (pi->refresh_rate == 0)
0d99a77de43b3f Evgenii Burenchev 2026-04-28 69 pi->refresh_rate = 60;
9d67006e6ebc6c Alex Deucher 2013-04-12 70 break;
9d67006e6ebc6c Alex Deucher 2013-04-12 71 }
9d67006e6ebc6c Alex Deucher 2013-04-12 72 }
9d67006e6ebc6c Alex Deucher 2013-04-12 73 }
9d67006e6ebc6c Alex Deucher 2013-04-12 74
--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH] drm/radeon/rs780: prevent division by zero in refresh rate calculation
2026-04-28 19:03 [PATCH] drm/radeon/rs780: prevent division by zero in refresh rate calculation Evgenii Burenchev
2026-04-29 19:04 ` kernel test robot
@ 2026-04-29 21:46 ` kernel test robot
1 sibling, 0 replies; 4+ messages in thread
From: kernel test robot @ 2026-04-29 21:46 UTC (permalink / raw)
To: Evgenii Burenchev, stable, Greg Kroah-Hartman
Cc: llvm, oe-kbuild-all, Evgenii Burenchev, alexander.deucher,
christian.koenig, airlied, simona, amd-gfx, dri-devel,
linux-kernel
Hi Evgenii,
kernel test robot noticed the following build warnings:
[auto build test WARNING on drm-misc/drm-misc-next]
[also build test WARNING on linus/master v7.1-rc1 next-20260429]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]
url: https://github.com/intel-lab-lkp/linux/commits/Evgenii-Burenchev/drm-radeon-rs780-prevent-division-by-zero-in-refresh-rate-calculation/20260429-055830
base: https://gitlab.freedesktop.org/drm/misc/kernel.git drm-misc-next
patch link: https://lore.kernel.org/r/20260428190318.34413-1-evg28bur%40yandex.ru
patch subject: [PATCH] drm/radeon/rs780: prevent division by zero in refresh rate calculation
config: riscv-defconfig (https://download.01.org/0day-ci/archive/20260430/202604300508.yXci8rey-lkp@intel.com/config)
compiler: clang version 23.0.0git (https://github.com/llvm/llvm-project 5bac06718f502014fade905512f1d26d578a18f3)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260430/202604300508.yXci8rey-lkp@intel.com/reproduce)
If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202604300508.yXci8rey-lkp@intel.com/
All warnings (new ones prefixed by >>):
>> drivers/gpu/drm/radeon/rs780_dpm.c:68:5: warning: misleading indentation; statement is not part of the previous 'if' [-Wmisleading-indentation]
68 | if (pi->refresh_rate == 0)
| ^
drivers/gpu/drm/radeon/rs780_dpm.c:66:4: note: previous statement is here
66 | if (crtc->mode.htotal && crtc->mode.vtotal)
| ^
1 warning generated.
vim +/if +68 drivers/gpu/drm/radeon/rs780_dpm.c
48
49 static void rs780_get_pm_mode_parameters(struct radeon_device *rdev)
50 {
51 struct igp_power_info *pi = rs780_get_pi(rdev);
52 struct radeon_mode_info *minfo = &rdev->mode_info;
53 struct drm_crtc *crtc;
54 struct radeon_crtc *radeon_crtc;
55 int i;
56
57 /* defaults */
58 pi->crtc_id = 0;
59 pi->refresh_rate = 60;
60
61 for (i = 0; i < rdev->num_crtc; i++) {
62 crtc = (struct drm_crtc *)minfo->crtcs[i];
63 if (crtc && crtc->enabled) {
64 radeon_crtc = to_radeon_crtc(crtc);
65 pi->crtc_id = radeon_crtc->crtc_id;
66 if (crtc->mode.htotal && crtc->mode.vtotal)
67 pi->refresh_rate = drm_mode_vrefresh(&crtc->mode);
> 68 if (pi->refresh_rate == 0)
69 pi->refresh_rate = 60;
70 break;
71 }
72 }
73 }
74
--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki
^ permalink raw reply [flat|nested] 4+ messages in thread
* [PATCH] drm/radeon/rs780: prevent division by zero in refresh rate calculation
@ 2026-04-30 10:46 Evgenii Burenchev
0 siblings, 0 replies; 4+ messages in thread
From: Evgenii Burenchev @ 2026-04-30 10:46 UTC (permalink / raw)
To: stable, Greg Kroah-Hartman
Cc: Evgenii Burenchev, kernel test robot, alexander.deucher,
christian.koenig, airlied, simona, amd-gfx, dri-devel,
linux-kernel
drm_mode_vrefresh() may return zero when mode clock is zero even if
htotal and vtotal are non-zero. Current code checks only htotal and
vtotal, allowing refresh_rate to become zero and subsequently causing
division by zero in rs780_program_at().
Fix by adding mode clock validation and fallback to default 60Hz in
rs780_get_pm_mode_parameters(). Add WARN_ON in rs780_program_at() to
catch such cases during development, ensuring safe fallback in all
scenarios.
Found by Linux Verification Center (linuxtesting.org) with SVACE.
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202604300508.yXci8rey-lkp@intel.com/
Signed-off-by: Evgenii Burenchev <evg28bur@yandex.ru>
---
drivers/gpu/drm/radeon/rs780_dpm.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/radeon/rs780_dpm.c b/drivers/gpu/drm/radeon/rs780_dpm.c
index 64bb4cafb8b5..8713f3fd6268 100644
--- a/drivers/gpu/drm/radeon/rs780_dpm.c
+++ b/drivers/gpu/drm/radeon/rs780_dpm.c
@@ -63,8 +63,11 @@ static void rs780_get_pm_mode_parameters(struct radeon_device *rdev)
if (crtc && crtc->enabled) {
radeon_crtc = to_radeon_crtc(crtc);
pi->crtc_id = radeon_crtc->crtc_id;
- if (crtc->mode.htotal && crtc->mode.vtotal)
+ if (crtc->mode.htotal && crtc->mode.vtotal) {
pi->refresh_rate = drm_mode_vrefresh(&crtc->mode);
+ if (pi->refresh_rate == 0)
+ pi->refresh_rate = 60;
+ }
break;
}
}
@@ -363,6 +366,8 @@ static void rs780_program_at(struct radeon_device *rdev)
{
struct igp_power_info *pi = rs780_get_pi(rdev);
+ WARN_ON(pi->refresh_rate == 0);
+
WREG32(FVTHROT_TARGET_REG, 30000000 / pi->refresh_rate);
WREG32(FVTHROT_CB1, 1000000 * 5 / pi->refresh_rate);
WREG32(FVTHROT_CB2, 1000000 * 10 / pi->refresh_rate);
base-commit: a5640267d6d35b89ebe6418da90a952a247215a5
--
2.43.0
^ permalink raw reply related [flat|nested] 4+ messages in thread
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2026-04-28 19:03 [PATCH] drm/radeon/rs780: prevent division by zero in refresh rate calculation Evgenii Burenchev
2026-04-29 19:04 ` kernel test robot
2026-04-29 21:46 ` kernel test robot
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