Re: [PATCH v1 2/2] drm/xe: Add sysfs for GT/IA bias

["Belgaumkar, Vinay" <vinay.belgaumkar@intel.com>]

On 7/3/2026 11:31 AM, Rodrigo Vivi wrote:
> On Wed, Jul 01, 2026 at 05:56:14PM -0700, Vinay Belgaumkar wrote:
>> GT_IA_PERF_BIAS_REG indicates power budget between IA and GT.
>> Lower 16 bits correspond to IA and upper to GT. Higher value
>> indicates more bias towards that plane. The values are in U1.15
>> format.
>>
>> $ cat /sys/class/drm/card1/device/tile0/gt0/freq0/gt_ia_bias
>> 0x80002666
> What about decoding this?

With the standard U1.15 format, this represents fractions with max value 
of 1. So, 0x8000 is decoded as 0x8000/2^15, which is 1. Every other 
number will be less than 1. I could add the decoding if that adds value.

Thanks,

Vinay.

>
>> This interface will allow us to observe power budget changes while
>> running workloads and also, if needed, tune it.
>>
>> Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
>> Signed-off-by: Vinay Belgaumkar <vinay.belgaumkar@intel.com>
>> ---
>>   drivers/gpu/drm/xe/regs/xe_gt_regs.h |  2 ++
>>   drivers/gpu/drm/xe/xe_gt_freq.c      | 51 ++++++++++++++++++++++++++++
>>   2 files changed, 53 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/xe/regs/xe_gt_regs.h b/drivers/gpu/drm/xe/regs/xe_gt_regs.h
>> index 08251c7a1a4b..41c5c5f20964 100644
>> --- a/drivers/gpu/drm/xe/regs/xe_gt_regs.h
>> +++ b/drivers/gpu/drm/xe/regs/xe_gt_regs.h
>> @@ -634,6 +634,8 @@
>>   #define GT_GFX_RC6_LOCKED			XE_REG(0x138104)
>>   #define GT_GFX_RC6				XE_REG(0x138108)
>>   
>> +#define GT_IA_PERF_BIAS_REG			XE_REG(0x138158)
>> +
>>   #define GT0_PERF_LIMIT_REASONS			XE_REG(0x1381a8)
>>   /* Common performance limit reason bits - available on all platforms */
>>   #define   GT0_PERF_LIMIT_REASONS_MASK		0xde3
>> diff --git a/drivers/gpu/drm/xe/xe_gt_freq.c b/drivers/gpu/drm/xe/xe_gt_freq.c
>> index a40dd074106f..0847832151f9 100644
>> --- a/drivers/gpu/drm/xe/xe_gt_freq.c
>> +++ b/drivers/gpu/drm/xe/xe_gt_freq.c
>> @@ -11,10 +11,13 @@
>>   #include <drm/drm_managed.h>
>>   #include <drm/drm_print.h>
>>   
>> +#include <regs/xe_gt_regs.h>
>> +#include "xe_gt.h"
>>   #include "xe_gt_sysfs.h"
>>   #include "xe_gt_throttle.h"
>>   #include "xe_gt_types.h"
>>   #include "xe_guc_pc.h"
>> +#include "xe_mmio.h"
>>   #include "xe_pm.h"
>>   
>>   /**
>> @@ -242,6 +245,41 @@ static ssize_t power_profile_store(struct kobject *kobj,
>>   }
>>   static struct kobj_attribute attr_power_profile = __ATTR_RW(power_profile);
>>   
>> +static ssize_t gt_ia_bias_show(struct kobject *kobj,
>> +			       struct kobj_attribute *attr,
>> +			       char *buf)
>> +{
>> +	struct device *dev = kobj_to_dev(kobj);
>> +	struct xe_gt *gt = kobj_to_gt(kobj->parent);
>> +	u32 val;
>> +
>> +	guard(xe_pm_runtime)(dev_to_xe(dev));
>> +	val = xe_mmio_read32(&gt->mmio, GT_IA_PERF_BIAS_REG);
>> +
>> +	return sysfs_emit(buf, "0x%x\n", val);
>> +}
>> +
>> +static ssize_t gt_ia_bias_store(struct kobject *kobj,
>> +				struct kobj_attribute *attr,
>> +				const char *buff, size_t count)
>> +{
>> +	struct device *dev = kobj_to_dev(kobj);
>> +	struct xe_gt *gt = kobj_to_gt(kobj->parent);
>> +	u32 val;
>> +	int ret;
>> +
>> +	ret = kstrtou32(buff, 0, &val);
>> +	if (ret)
>> +		return ret;
>> +
>> +	guard(xe_pm_runtime)(dev_to_xe(dev));
>> +	xe_mmio_write32(&gt->mmio, GT_IA_PERF_BIAS_REG, val);
>> +
>> +	return count;
>> +}
>> +
>> +static struct kobj_attribute attr_gt_ia_bias = __ATTR_RW(gt_ia_bias);
>> +
>>   static const struct attribute *freq_attrs[] = {
>>   	&attr_act_freq.attr,
>>   	&attr_cur_freq.attr,
>> @@ -258,8 +296,13 @@ static const struct attribute *freq_attrs[] = {
>>   static void freq_fini(void *arg)
>>   {
>>   	struct kobject *kobj = arg;
>> +	struct device *dev = kobj_to_dev(kobj);
>> +	struct xe_gt *gt = kobj_to_gt(kobj->parent);
>>   
>>   	sysfs_remove_files(kobj, freq_attrs);
>> +
>> +	if (xe_gt_is_main_type(gt) && !IS_DGFX(dev_to_xe(dev)))
>> +		sysfs_remove_file(kobj, &attr_gt_ia_bias.attr);
>>   	kobject_put(kobj);
>>   }
>>   
>> @@ -289,6 +332,14 @@ int xe_gt_freq_init(struct xe_gt *gt)
>>   		return err;
>>   	}
>>   
>> +	if (xe_gt_is_main_type(gt) && !IS_DGFX(xe)) {
>> +		err = sysfs_create_file(gt->freq, &attr_gt_ia_bias.attr);
>> +		if (err) {
>> +			kobject_put(gt->freq);
>> +			return err;
>> +		}
>> +	}
>> +
>>   	err = devm_add_action_or_reset(xe->drm.dev, freq_fini, gt->freq);
>>   	if (err)
>>   		return err;
>> -- 
>> 2.38.1
>>