https://bugs.kde.org/show_bug.cgi?id=521240
Bug ID: 521240
Summary: gpu/gpu1/memoryFrequency sensor reports 0 MHz on AMD
RDNA4 (RX 9070 XT) under 3D load
Classification: Frameworks and Libraries
Product: ksystemstats
Version First unspecified
Reported In:
Platform: CachyOS
OS: Linux
Status: REPORTED
Severity: normal
Priority: NOR
Component: General
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected]
Target Milestone: ---
The System Monitor Sensor widget (gpu/gpu1/memoryFrequency) always displays 0
MHz for the GPU memory frequency while a 3D workload (e.g. FurMark, games) is
running. At idle, the sensor reports the correct value.
== Root cause ==
LinuxAmdGpu.cpp reads the current memory clock via ppTableGetCurrent(), which
parses /sys/class/drm/card1/device/pp_dpm_mclk and looks for the line marked
with *:
int ppTableGetCurrent(const QByteArray &table) {
int current = 0;
for (const auto &line : lines) {
if (!line.contains("*")) continue;
current = std::atoi(line.mid(line.indexOf(":") + 1));
}
return current; // returns 0 if no "*" found
}
On RDNA4 (Navi 48), the AMDGPU kernel driver does NOT set the * marker in
pp_dpm_mclk during active 3D rendering. The file content during 3D load:
0: 96Mhz
1: 456Mhz
2: 772Mhz
3: 875Mhz
4: 1124Mhz
5: 1258Mhz
No * on any line → ppTableGetCurrent() returns 0 → sensor reports 0 MHz.
At idle, * is present and the sensor works correctly:
0: 96Mhz *
The hwmon interface reports the correct current frequency at all times
(including under 3D load):
/sys/class/hwmon/hwmonN/freq2_input (label: mclk, value in Hz)
This issue does NOT occur on RDNA2 (RX 6800 XT) — that driver always marks the
active state with *.
== Steps to reproduce ==
1. System with AMD RDNA4 GPU (e.g. RX 9070 XT, PCI ID 1002:7550)
2. Add a System Monitor Sensor widget configured to show
gpu/gpu1/memoryFrequency
3. Launch a 3D workload (FurMark, a game, etc.)
4. Observe the widget showing 0 MHz for the entire duration of the workload
== Expected behavior ==
Widget shows the actual GPU memory frequency (e.g. up to 1258 MHz per DPM
table)
== Actual behavior ==
Widget shows 0 MHz under any 3D load
== Suggested fix ==
Fall back to reading freq2_input from the hwmon sysfs interface when
ppTableGetCurrent() returns 0 (i.e. when no * marker is found). The hwmon path
for the AMDGPU memory clock is hwmon/hwmonN/freq2_input (value in Hz, label
"mclk"). Alternatively, prefer hwmon freq2_input over pp_dpm_mclk for current
frequency reporting on RDNA4+ hardware, as it is always up to date.
== System information ==
- GPU: AMD Radeon RX 9070 XT (Navi 48, 1002:7550 rev c0)
- Kernel: 7.0.11-1-cachyos (AMDGPU built-in)
- ksystemstats: 6.6.5-2.1
- KDE Plasma: 6.6.5
- OS: Arch Linux (CachyOS)
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