Re: [PATCH] drm/xe/hwmon: refresh Battlemage thermal telemetry under force-wake

[Constantinos Chalkias <cch@e-psn.eu>]

Thanks for catching this.
On the B70 I observed two distinct symptoms after a sustained workload:
- package/VRAM temperature values could remain stale while the physical 
blower stayed elevated even after the device had returned to idle;
- fan1_input could independently report implausibly low or zero RPM 
while the physical blower was still running fast.
This patch only addresses the temperature MMIO path. Holding XE_FW_GT 
for a short settling interval before the temperature read causes the 
temperature telemetry to refresh and, in my testing, the physical blower 
then settles normally as well.
The REG_FAN_SPEED path remains a separate direct MMIO read and can still 
show unreliable values, so the current patch should not be read as 
fixing fan RPM telemetry itself.
I can reword the commit message in a v2 to make that distinction 
explicit, and investigate the fan telemetry path separately.

On 2026-10-12 13:59, sashiko-bot@kernel.org wrote:
> Thank you for your contribution! Sashiko AI review found 1 potential 
> issue(s) to consider:
> - [Medium] drm/xe: fan telemetry lacks Battlemage thermal force-wake 
> workaround
> --
> 
> commit a9faaf30cbf789280ad52add1cf188270e8ccad9
> Author: Constantinos Chalkias <cch@e-psn.eu>
> 
> drm/xe/hwmon: refresh Battlemage thermal telemetry under force-wake
> 
> This commit works around stale thermal telemetry on Battlemage by
> acquiring the GT force-wake domain and waiting 500-1000 us before
> reading temperature registers.
> 
>> drm/xe/hwmon: refresh Battlemage thermal telemetry under force-wake
>> 
>> On Battlemage, thermal telemetry can remain stale after the GT returns
>> to RC6 following sustained workloads.
>> 
>> On an Intel Arc Pro B70, package and VRAM temperature telemetry may 
>> stop
>> refreshing after a long inference workload. Fan telemetry can also
>> become invalid while the physical blower remains elevated.
> 
> [Severity: Medium]
> The commit message states that fan telemetry can become invalid, but 
> the
> patch only applies the force-wake and delay workaround to temperature 
> and
> VRAM channels via xe_hwmon_temp_mmio_read().
> 
> Does xe_hwmon_fan_input_read() also need this workaround? Currently, it
> continues to read REG_FAN_SPEED directly via xe_mmio_read32() without
> acquiring force-wake or delaying:
> 
> drivers/gpu/drm/xe/xe_hwmon.c:xe_hwmon_fan_input_read() {
>     ...
> 	mutex_lock(&hwmon->hwmon_lock);
> 
> 	reg_val = xe_mmio_read32(mmio, xe_hwmon_get_reg(hwmon, REG_FAN_SPEED, 
> channel));
> 	time_now = get_jiffies_64();
>     ...
> }
> 
> Will fan telemetry still remain susceptible to staleness on Battlemage
> without the workaround?