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

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

Hi Rodrigo,
Thanks for pointing this out. Yes, this appears to be the same issue, 
and I agree we should avoid parallel fixes.
My follow-up testing independently converged on a very similar result. I 
narrowed the workaround to CHANNEL_PKG only. A 500-1000 us GT force-wake 
interval was not reliable, while 3000-3500 us was.
In the most controlled test I disabled both hwmon pollers, stopped the 
inference workload, and the physical blower remained latched at high 
speed for more than five minutes while the GPU was otherwise idle. A 
single package-temperature read using XE_FW_GT with a 3000-3500 us 
interval immediately caused the blower to return to normal.
I also saw the later RFC follow-up showing that both GT-only and 
RENDER-only longer pulses could refresh the telemetry and were followed 
by fan slowdown, which seems consistent with this result.
I won't send a competing v2. I'm happy to contribute these measurements 
to the existing RFC effort and help test whatever implementation you 
prefer to converge on.
Thanks,
Constantinos

On 2026-10-14 23:12, Rodrigo Vivi wrote:
> On Mon, Oct 12, 2026 at 01:42:45PM +0300, Constantinos Chalkias wrote:
>> 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.
>> 
>> Acquire the GT force-wake domain around Battlemage thermal MMIO reads
>> and allow a short settling interval before reading the register. Route
>> package, VRAM and VRAM-channel availability reads through the helper.
>> 
>> Testing showed that an immediate read, as well as a 100-300 us delay,
>> could leave telemetry stale. A 500-1000 us delay recovered correctly
>> across repeated inference-to-idle cycles.
>> 
>> The change is restricted to Battlemage, where the behavior has been
>> reproduced and validated.
>> 
>> Signed-off-by: Constantinos Chalkias <cch@e-psn.eu>
> 
> Cc: Bata Roland Krisztián <batarolandkrisztian@gmail.com>
> 
> https://lore.kernel.org/intel-xe/179041811564.526373.13204522833274380927.b70-hwmon-rfc@gmail.com/
> 
> I believe you guys are facing the same dificulties and arriving to 
> similar
> conclusions.
> 
> If the consensus is that we need this forcewake, let's do it.
> 
> Let's just avoid duplication of efforts in here.
> 
> And thank you all for the contributions.
> 
>> ---
>>  drivers/gpu/drm/xe/xe_hwmon.c | 51 
>> ++++++++++++++++++++++++++++++-----
>>  1 file changed, 45 insertions(+), 6 deletions(-)
>> 
>> diff --git a/drivers/gpu/drm/xe/xe_hwmon.c 
>> b/drivers/gpu/drm/xe/xe_hwmon.c
>> index 5edeac961ec3..fee358ab9a6b 100644
>> --- a/drivers/gpu/drm/xe/xe_hwmon.c
>> +++ b/drivers/gpu/drm/xe/xe_hwmon.c
>> @@ -3,6 +3,7 @@
>>   * Copyright © 2023 Intel Corporation
>>   */
>> 
>> +#include <linux/delay.h>
>>  #include <linux/hwmon-sysfs.h>
>>  #include <linux/hwmon.h>
>>  #include <linux/jiffies.h>
>> @@ -14,6 +15,7 @@
>>  #include "regs/xe_mchbar_regs.h"
>>  #include "regs/xe_pcode_regs.h"
>>  #include "xe_device.h"
>> +#include "xe_force_wake.h"
>>  #include "xe_hwmon.h"
>>  #include "xe_mmio.h"
>>  #include "xe_pcode.h"
>> @@ -946,14 +948,43 @@ static void xe_hwmon_get_voltage(struct xe_hwmon 
>> *hwmon, int channel, long *valu
>>  	*value = DIV_ROUND_CLOSEST(REG_FIELD_GET(VOLTAGE_MASK, reg_val) * 
>> 2500, SF_VOLTAGE);
>>  }
>> 
>> -static inline bool is_vram_ch_available(struct xe_hwmon *hwmon, int 
>> channel)
>> +static int xe_hwmon_temp_mmio_read(struct xe_hwmon *hwmon,
>> +				   struct xe_reg reg, u32 *reg_val)
>>  {
>>  	struct xe_mmio *mmio = xe_root_tile_mmio(hwmon->xe);
>> +
>> +	if (hwmon->xe->info.platform == XE_BATTLEMAGE) {
>> +		struct xe_gt *gt = xe_root_mmio_gt(hwmon->xe);
>> +
>> +		CLASS(xe_force_wake, fw_ref)(gt_to_fw(gt), XE_FW_GT);
>> +
>> +		if (!xe_force_wake_ref_has_domain(fw_ref.domains, XE_FW_GT))
>> +			return -ETIMEDOUT;
>> +
>> +		/*
>> +		 * Allow thermal telemetry to refresh after leaving RC6
>> +		 * before reading the temperature register.
>> +		 */
>> +		usleep_range(500, 1000);
>> +
>> +		*reg_val = xe_mmio_read32(mmio, reg);
>> +		return 0;
>> +	}
>> +
>> +	*reg_val = xe_mmio_read32(mmio, reg);
>> +
>> +	return 0;
>> +}
>> +
>> +static inline bool is_vram_ch_available(struct xe_hwmon *hwmon, int 
>> channel)
>> +{
>>  	int vram_id = channel - CHANNEL_VRAM_N;
>>  	struct xe_reg vram_reg;
>> +	u32 reg_val;
>> 
>>  	vram_reg = xe_hwmon_get_reg(hwmon, REG_TEMP, channel);
>> -	if (!xe_reg_is_valid(vram_reg) || !xe_mmio_read32(mmio, vram_reg))
>> +	if (!xe_reg_is_valid(vram_reg) ||
>> +	    xe_hwmon_temp_mmio_read(hwmon, vram_reg, &reg_val) || !reg_val)
>>  		return false;
>> 
>>  	/* Create label only for available vram channel */
>> @@ -1025,15 +1056,19 @@ xe_hwmon_temp_is_visible(struct xe_hwmon 
>> *hwmon, u32 attr, int channel)
>>  static int
>>  xe_hwmon_temp_read(struct xe_hwmon *hwmon, u32 attr, int channel, 
>> long *val)
>>  {
>> -	struct xe_mmio *mmio = xe_root_tile_mmio(hwmon->xe);
>> -	u64 reg_val;
>> +	u32 reg_val;
>> +	int ret;
>> 
>>  	switch (attr) {
>>  	case hwmon_temp_input:
>>  		switch (channel) {
>>  		case CHANNEL_PKG:
>>  		case CHANNEL_VRAM:
>> -			reg_val = xe_mmio_read32(mmio, xe_hwmon_get_reg(hwmon, REG_TEMP, 
>> channel));
>> +			ret = xe_hwmon_temp_mmio_read(hwmon,
>> +						      xe_hwmon_get_reg(hwmon, REG_TEMP, channel),
>> +						      &reg_val);
>> +			if (ret)
>> +				return ret;
>> 
>>  			/* HW register value is in degrees Celsius, convert to 
>> millidegrees. */
>>  			*val = REG_FIELD_GET(TEMP_MASK, reg_val) * MILLIDEGREE_PER_DEGREE;
>> @@ -1043,7 +1078,11 @@ xe_hwmon_temp_read(struct xe_hwmon *hwmon, u32 
>> attr, int channel, long *val)
>>  		case CHANNEL_PCIE:
>>  			return get_pcie_temp(hwmon, val);
>>  		case CHANNEL_VRAM_N...CHANNEL_VRAM_N_MAX:
>> -			reg_val = xe_mmio_read32(mmio, xe_hwmon_get_reg(hwmon, REG_TEMP, 
>> channel));
>> +			ret = xe_hwmon_temp_mmio_read(hwmon,
>> +						      xe_hwmon_get_reg(hwmon, REG_TEMP, channel),
>> +						      &reg_val);
>> +			if (ret)
>> +				return ret;
>>  			/*
>>  			 * This temperature format is 24 bit [31:8] signed integer and 8 
>> bit
>>  			 * [7:0] fraction.
>> --
>> 2.56.0
>>