From ea8439751ddc3af189121100631554ebe4bbb2d4 Mon Sep 17 00:00:00 2001 From: Zhan Wei Date: Wed, 3 Jun 2026 00:17:07 +0800 Subject: [PATCH] drm/xe/hwmon: document DG2 fan speed reporting quirk 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. Fixes: 28f79ac609de ("drm/xe/hwmon: expose fan speed") Signed-off-by: Zhan Wei Reviewed-by: Raag Jadav Link: https://patch.msgid.link/20260602161707.18922-1-zhanwei919@gmail.com Signed-off-by: Rodrigo Vivi --- 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/fan3_input Date: March 2025 KernelVersion: 6.16