On DG2 the driver always shows two fan channels, because the FSC_READ_NUM_FANS command does not work on some cards. OEMs decide how the fans map to tach channels, so two fans can share one tach line. When that happens, the second channel reads 0 RPM even though the fan is spinning.
Note this on the fan2_input ABI entry so the steady 0 RPM is not mistaken for a driver bug. Signed-off-by: Zhan Wei <[email protected]> --- v3: - Drop the dedicated Documentation/gpu/xe/xe_hwmon.rst doc and the index.rst hunk; add a short note under the fan2_input entry in the existing ABI doc instead, per Raag's feedback. v2: https://lore.kernel.org/intel-xe/[email protected]/ - Drop the code change that reported a single fan on DG2; document the shared-tach behaviour instead, per review feedback on v1. v1: https://lore.kernel.org/intel-xe/[email protected]/ Documentation/ABI/testing/sysfs-driver-intel-xe-hwmon | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/Documentation/ABI/testing/sysfs-driver-intel-xe-hwmon b/Documentation/ABI/testing/sysfs-driver-intel-xe-hwmon index 55ab45f669ac..0da739d9a816 100644 --- a/Documentation/ABI/testing/sysfs-driver-intel-xe-hwmon +++ b/Documentation/ABI/testing/sysfs-driver-intel-xe-hwmon @@ -251,6 +251,13 @@ Description: RO. Fan 2 speed in RPM. Only supported for particular Intel Xe graphics platforms. + On DG2 the driver always shows two fan channels, because the + FSC_READ_NUM_FANS command does not work on some cards. OEMs + decide how the fans map to tach channels, so two fans can share + one tach line. When that happens, the second channel + reads 0 RPM even though the fan is spinning. This is normal, not + a bug. + What: /sys/bus/pci/drivers/xe/.../hwmon/hwmon<i>/fan3_input Date: March 2025 KernelVersion: 6.16 -- 2.43.0
