Re: [PATCH v4 1/1] drm/i915/dg1: Add HWMON power sensor support

["Sundaresan, Sujaritha" <sujaritha.sundaresan@xxxxxxxxx>]

On 5/27/2021 5:44 PM, Dale B Stimson wrote:
> As part of the System Managemenent Interface (SMI), use the HWMON
> subsystem to display power utilization.
>
> The following standard HWMON power sensors are currently supported
> (and appropriately scaled):
>    /sys/class/drm/card0/device/hwmon/hwmon<i>
> 	- energy1_input
> 	- power1_cap
> 	- power1_max
>
> Some non-standard HWMON power information is also provided, such as
> enable bits and intervals.
>
> Signed-off-by: Dale B Stimson <dale.b.stimson@xxxxxxxxx>
> ---
>   .../ABI/testing/sysfs-driver-intel-i915-hwmon | 116 +++
>   drivers/gpu/drm/i915/Kconfig                  |   1 +
>   drivers/gpu/drm/i915/Makefile                 |   1 +
>   drivers/gpu/drm/i915/i915_drv.c               |   6 +
>   drivers/gpu/drm/i915/i915_drv.h               |   3 +
>   drivers/gpu/drm/i915/i915_hwmon.c             | 757 ++++++++++++++++++
>   drivers/gpu/drm/i915/i915_hwmon.h             |  42 +
>   drivers/gpu/drm/i915/i915_reg.h               |  52 ++
>   8 files changed, 978 insertions(+)
>   create mode 100644 Documentation/ABI/testing/sysfs-driver-intel-i915-hwmon
>   create mode 100644 drivers/gpu/drm/i915/i915_hwmon.c
>   create mode 100644 drivers/gpu/drm/i915/i915_hwmon.h
>
> diff --git a/Documentation/ABI/testing/sysfs-driver-intel-i915-hwmon b/Documentation/ABI/testing/sysfs-driver-intel-i915-hwmon
> new file mode 100644
> index 0000000000000..2ee7c413ca190
> --- /dev/null
> +++ b/Documentation/ABI/testing/sysfs-driver-intel-i915-hwmon
> @@ -0,0 +1,116 @@
> +What:           /sys/devices/.../hwmon/hwmon<i>/energy1_input
> +Date:           June 2021
> +KernelVersion:  5.14
> +Contact:        dri-devel@xxxxxxxxxxxxxxxxxxxxx
> +Description:
> +                RO. Energy input of device in microjoules.
> +
> +		The returned textual representation is an unsigned integer
> +		number that can be stored in 64-bits.  Warning: The hardware
> +		register is 32-bits wide and can overflow by wrapping around.
> +		A single wrap-around between calls to read this value can
> +		be detected and will be accounted for in the returned value.
> +		At a power consumption of 1 watt, the 32-bit hardware register
> +		would wrap-around approximately every 3 days.
> +
> +		Only supported for particular Intel i915 graphics platforms.
> +
> +What:           /sys/devices/.../hwmon/hwmon<i>/power1_max_enable
> +Date:           June 2021
> +KernelVersion:  5.14
> +Contact:        dri-devel@xxxxxxxxxxxxxxxxxxxxx
> +Description:
> +                RW.  Sustained power limit is enabled - true or false.

Hi Dale,

This attribute should be read-only ?

> +
> +                The power controller will throttle the operating frequency
> +                if the power averaged over a window (typically seconds)
> +                exceeds this limit.
> +
> +                See power1_max_enable power1_max power1_max_interval
> +
> +		Only supported for particular Intel i915 graphics platforms.
> +
> +What:           /sys/devices/.../hwmon/hwmon<i>/power1_max
> +Date:           June 2021
> +KernelVersion:  5.14
> +Contact:        dri-devel@xxxxxxxxxxxxxxxxxxxxx
> +Description:
> +                RW.  Sustained power limit in milliwatts
> +
> +                The power controller will throttle the operating frequency
> +                if the power averaged over a window (typically seconds)
> +                exceeds this limit.
> +
> +                See power1_max_enable power1_max power1_max_interval
> +
> +		Only supported for particular Intel i915 graphics platforms.
> +
> +What:           /sys/devices/.../hwmon/hwmon<i>/power1_max_interval
> +Date:           June 2021
> +KernelVersion:  5.14
> +Contact:        dri-devel@xxxxxxxxxxxxxxxxxxxxx
> +Description:
> +                RW. Sustained power limit interval in milliseconds over
> +                which sustained power is averaged.
> +
> +                See power1_max_enable power1_max power1_max_interval
> +
> +		Only supported for particular Intel i915 graphics platforms.
> +
> +What:           /sys/devices/.../hwmon/hwmon<i>/power1_cap_enable
> +Date:           June 2021
> +KernelVersion:  5.14
> +Contact:        dri-devel@xxxxxxxxxxxxxxxxxxxxx
> +Description:
> +		RW.  Power burst limit is enabled - true or false
> +
> +                See power1_cap_enable power1_cap
> +
> +		Only supported for particular Intel i915 graphics platforms.
> +
> +What:           /sys/devices/.../hwmon/hwmon<i>/power1_cap
> +Date:           June 2021
> +KernelVersion:  5.14
> +Contact:        dri-devel@xxxxxxxxxxxxxxxxxxxxx
> +Description:
> +		RW.  Power burst limit in milliwatts.
> +
> +                See power1_cap_enable power1_cap
> +
> +		Only supported for particular Intel i915 graphics platforms.
> +
> +What:           /sys/devices/.../hwmon/hwmon<i>/power_default_limit
> +Date:           June 2021
> +KernelVersion:  5.14
> +Contact:        dri-devel@xxxxxxxxxxxxxxxxxxxxx
> +Description:
> +                RO.  Default power limit.
> +
> +		Only supported for particular Intel i915 graphics platforms.
> +
> +What:           /sys/devices/.../hwmon/hwmon<i>/power_min_limit
> +Date:           June 2021
> +KernelVersion:  5.14
> +Contact:        dri-devel@xxxxxxxxxxxxxxxxxxxxx
> +Description:
> +                RO.  Default minimum power limit.
> +
> +		Only supported for particular Intel i915 graphics platforms.
> +
> +		If not supported, then attribute will be absent, or attempted
> +		access will give error return or return value as 0.
> +
> +What:           /sys/devices/.../hwmon/hwmon<i>/power_max_limit
> +Date:           June 2021
> +KernelVersion:  5.14
> +Contact:        dri-devel@xxxxxxxxxxxxxxxxxxxxx
> +Description:
> +                RO.  Default maximum power limit.
> +
> +		Only supported for particular Intel i915 graphics platforms.
> +
> +		If not supported, then one of: absent, error return or value
> +		returned as 0 or UINT_MAX.
> +
> +		If not supported, then attribute will be absent, or attempted
> +		access will give error return or return value as 0 or UINT_MAX.
> diff --git a/drivers/gpu/drm/i915/Kconfig b/drivers/gpu/drm/i915/Kconfig
> index 93f4d059fc89f..cd1b9b406c725 100644
> --- a/drivers/gpu/drm/i915/Kconfig
> +++ b/drivers/gpu/drm/i915/Kconfig
> @@ -14,6 +14,7 @@ config DRM_I915
>   	select DRM_MIPI_DSI
>   	select RELAY
>   	select IRQ_WORK
> +	select HWMON
>   	# i915 depends on ACPI_VIDEO when ACPI is enabled
>   	# but for select to work, need to select ACPI_VIDEO's dependencies, ick
>   	select BACKLIGHT_CLASS_DEVICE if ACPI
> diff --git a/drivers/gpu/drm/i915/Makefile b/drivers/gpu/drm/i915/Makefile
> index 6947495bf34b8..993c0a9943ef8 100644
> --- a/drivers/gpu/drm/i915/Makefile
> +++ b/drivers/gpu/drm/i915/Makefile
> @@ -37,6 +37,7 @@ i915-y += i915_drv.o \
>   	  i915_config.o \
>   	  i915_irq.o \
>   	  i915_getparam.o \
> +	  i915_hwmon.o \
>   	  i915_mitigations.o \
>   	  i915_params.o \
>   	  i915_pci.o \
> diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
> index 2f06bb7b3ed2c..3636755622c37 100644
> --- a/drivers/gpu/drm/i915/i915_drv.c
> +++ b/drivers/gpu/drm/i915/i915_drv.c
> @@ -70,6 +70,7 @@
>   
>   #include "i915_debugfs.h"
>   #include "i915_drv.h"
> +#include "i915_hwmon.h"
>   #include "i915_ioc32.h"
>   #include "i915_irq.h"
>   #include "i915_memcpy.h"
> @@ -681,6 +682,8 @@ static void i915_driver_register(struct drm_i915_private *dev_priv)
>   
>   	intel_gt_driver_register(&dev_priv->gt);
>   
> +	i915_hwmon_register(dev_priv);
> +
>   	intel_display_driver_register(dev_priv);
>   
>   	intel_power_domains_enable(dev_priv);
> @@ -707,9 +710,12 @@ static void i915_driver_unregister(struct drm_i915_private *dev_priv)
>   
>   	intel_display_driver_unregister(dev_priv);
>   
> +	i915_hwmon_unregister(dev_priv);
> +
>   	intel_gt_driver_unregister(&dev_priv->gt);
>   
>   	i915_perf_unregister(dev_priv);
> +
>   	i915_pmu_unregister(dev_priv);
>   
>   	i915_teardown_sysfs(dev_priv);
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index 0f6d27da69acd..f0476908e0359 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -60,6 +60,7 @@
>   #include <drm/drm_connector.h>
>   #include <drm/i915_mei_hdcp_interface.h>
>   
> +#include "i915_hwmon.h"
>   #include "i915_params.h"
>   #include "i915_reg.h"
>   #include "i915_utils.h"
> @@ -1118,6 +1119,8 @@ struct drm_i915_private {
>   
>   	struct i915_perf perf;
>   
> +	struct i915_hwmon hwmon;
> +
>   	/* Abstract the submission mechanism (legacy ringbuffer or execlists) away */
>   	struct intel_gt gt;
>   
> diff --git a/drivers/gpu/drm/i915/i915_hwmon.c b/drivers/gpu/drm/i915/i915_hwmon.c
> new file mode 100644
> index 0000000000000..e9e532fcf9d1e
> --- /dev/null
> +++ b/drivers/gpu/drm/i915/i915_hwmon.c
> @@ -0,0 +1,757 @@
> +// SPDX-License-Identifier: MIT
> +/*
> + * Copyright © 2020 Intel Corporation
> + */
> +
> +/*
> + * Power-related hwmon entries.
> + */
> +
> +#include <linux/hwmon.h>
> +#include <linux/hwmon-sysfs.h>
> +#include <linux/types.h>
> +
> +#include "i915_drv.h"
> +#include "gt/intel_gt.h"
> +#include "i915_hwmon.h"
> +
> +/*
> + * SF_* - scale factors for particular quantities.
> + * The hwmon standard says that quantities of the given types are specified
> + * in the given units:
> + * - time   - milliseconds
> + * - power  - microwatts
> + * - energy - microjoules
> + */
> +
> +#define SF_TIME		   1000
Maybe just me, but is the indent supposed to be different from the ones 
below ?
> +#define SF_POWER	1000000
> +#define SF_ENERGY	1000000
> +
> +#define FIELD_SHIFT(__mask)				    \
> +	(BUILD_BUG_ON_ZERO(!__builtin_constant_p(__mask)) + \
> +		BUILD_BUG_ON_ZERO((__mask) == 0) +	    \
> +		__bf_shf(__mask))
> +
> +static void
> +_locked_with_pm_intel_uncore_rmw(struct intel_uncore *uncore,
> +				 i915_reg_t reg, u32 clear, u32 set)
> +{
> +	struct drm_i915_private *i915 = uncore->i915;
> +	struct i915_hwmon *hwmon = &i915->hwmon;
> +	intel_wakeref_t wakeref;
> +
> +	mutex_lock(&hwmon->hwmon_lock);
> +
> +	with_intel_runtime_pm(uncore->rpm, wakeref)
> +		intel_uncore_rmw(uncore, reg, clear, set);
> +
> +	mutex_unlock(&hwmon->hwmon_lock);
> +}
> +
> +/*
> + * This function's return type of u64 allows for the case where the scaling
> + * of the field taken from the 32-bit register value might cause a result to
> + * exceed 32 bits.
> + */
> +static u64
> +_field_read_and_scale(struct intel_uncore *uncore, i915_reg_t rgadr,
> +		      u32 field_msk, int field_shift,
> +		      int nshift, unsigned int scale_factor)
> +{
> +	intel_wakeref_t wakeref;
> +	u32 reg_value;
> +	u64 scaled_val;
> +
> +	with_intel_runtime_pm(uncore->rpm, wakeref)
> +		reg_value = intel_uncore_read(uncore, rgadr);
> +
> +	reg_value = (reg_value & field_msk) >> field_shift;

Any reason why le32_get_bits won't work here ?

Thanks,

Suja

> +	scaled_val = mul_u32_u32(scale_factor, reg_value);
> +
> +	/* Shift, rounding to nearest */
> +	if (nshift > 0)
> +		scaled_val = (scaled_val + (1 << (nshift - 1))) >> nshift;
> +
> +	return scaled_val;
> +}
> +
> +static u64
> +_field_read64_and_scale(struct intel_uncore *uncore, i915_reg_t rgadr,
> +			u64 field_msk, int field_shift,
> +			int nshift, unsigned int scale_factor)
> +{
> +	intel_wakeref_t wakeref;
> +	u64 reg_value;
> +	u64 scaled_val;
> +
> +	with_intel_runtime_pm(uncore->rpm, wakeref)
> +		reg_value = intel_uncore_read64(uncore, rgadr);
> +
> +	reg_value = (reg_value & field_msk) >> field_shift;
> +	scaled_val = scale_factor * reg_value;
> +
> +	/* Shift, rounding to nearest */
> +	if (nshift > 0)
> +		scaled_val = (scaled_val + (1 << (nshift - 1))) >> nshift;
> +
> +	return scaled_val;
> +}
> +
> +static void
> +_field_scale_and_write(struct intel_uncore *uncore,
> +		       i915_reg_t rgadr,
> +		       u32 field_msk, int field_shift,
> +		       int nshift, unsigned int scale_factor, long lval)
> +{
> +	u32 nval;
> +	u32 bits_to_clear;
> +	u32 bits_to_set;
> +
> +	/* Computation in 64-bits to avoid overflow. Round to nearest. */
> +	nval = DIV_ROUND_CLOSEST_ULL((u64)lval << nshift, scale_factor);
> +
> +	bits_to_clear = field_msk;
> +	bits_to_set = (nval << field_shift) | field_msk;
> +
> +	_locked_with_pm_intel_uncore_rmw(uncore, rgadr,
> +					 bits_to_clear, bits_to_set);
> +}
> +
> +/*
> + * i915_energy1_input_show - A custom function to obtain energy1_input.
> + * Use a custom function instead of the usual hwmon helpers in order to
> + * guarantee 64-bits of result to user-space.
> + * Units are microjoules.
> + *
> + * The underlying hardware register is 32-bits and is subject to overflow.
> + * This function compensates for overflow of the 32-bit register by detecting
> + * wrap-around and incrementing an overflow counter.
> + * This only works if the register is sampled often enough to avoid
> + * missing an instance of overflow - achieved either by repeated
> + * queries through the API, or via a possible timer (future - TBD) that
> + * ensures values are read often enough to catch all overflows.
> + *
> + * How long before overflow?  For example, with an example scaling bit
> + * shift of 14 bits (see register *PACKAGE_POWER_SKU_UNIT) and a power draw of
> + * 1000 watts, the 32-bit counter will overflow in approximately 4.36 minutes.
> + *
> + * Examples:
> + *    1 watt:  (2^32 >> 14) /    1 W / (60 * 60 * 24) secs/day -> 3 days
> + * 1000 watts: (2^32 >> 14) / 1000 W / 60             secs/min -> 4.36 minutes
> + */
> +static ssize_t
> +i915_energy1_input_show(struct device *dev, struct device_attribute *attr,
> +			char *buf)
> +{
> +	struct drm_i915_private *i915 = dev_get_drvdata(dev);
> +	struct intel_uncore *uncore = &i915->uncore;
> +	struct i915_hwmon *hwmon = &i915->hwmon;
> +	int nshift = hwmon->scl_shift_energy;
> +	ssize_t ret;
> +	intel_wakeref_t wakeref;
> +	u32 reg_value;
> +	u64 vlo;
> +	u64 vhi;
> +
> +	mutex_lock(&hwmon->hwmon_lock);
> +
> +	with_intel_runtime_pm(uncore->rpm, wakeref)
> +		reg_value = intel_uncore_read(uncore,
> +					      hwmon->rg.pkg_energy_status);
> +
> +	/*
> +	 * The u32 register concatenated with the u32 overflow counter
> +	 * gives an effective energy counter size of 64-bits.  However, the
> +	 * computations below are done modulo 2^96 to avoid overflow during
> +	 * scaling in the conversion to microjoules.
> +	 *
> +	 * The low-order 64-bits of the resulting quantity are returned to
> +	 * the caller in units of microjoules, encoded into a decimal string.
> +	 *
> +	 * For a power of 1000 watts, 64 bits in units of microjoules will
> +	 * overflow after 584 years.
> +	 */
> +
> +	if (hwmon->energy_counter_prev > reg_value)
> +		hwmon->energy_counter_overflow++;
> +
> +	hwmon->energy_counter_prev = reg_value;
> +
> +	/*
> +	 * 64-bit variables vlo and vhi are used for the scaling process.
> +	 * The 96-bit counter value is composed from the two 64-bit variables
> +	 * vhi and vlo thusly:  counter == vhi << 32 + vlo .
> +	 * The 32-bits of overlap between the two variables is convenient for
> +	 * handling overflows out of vlo.
> +	 */
> +
> +	vlo = reg_value;
> +	vhi = hwmon->energy_counter_overflow;
> +
> +	mutex_unlock(&hwmon->hwmon_lock);
> +
> +	vlo = SF_ENERGY * vlo;
> +
> +	/* Prepare to round to nearest */
> +	if (nshift > 0)
> +		vlo += 1 << (nshift - 1);
> +
> +	/*
> +	 * Anything in the upper-32 bits of vlo gets added into vhi here,
> +	 * and then cleared from vlo.
> +	 */
> +	vhi = (SF_ENERGY * vhi) + (vlo >> 32);
> +	vlo &= 0xffffffffULL;
> +
> +	/*
> +	 * Apply the right shift.
> +	 * - vlo shifted by itself.
> +	 * - vlo receiving what's shifted out of vhi.
> +	 * - vhi shifted by itself
> +	 */
> +	vlo = vlo >> nshift;
> +	vlo |= (vhi << (32 - nshift)) & 0xffffffffULL;
> +	vhi = vhi >> nshift;
> +
> +	/* Combined to get a 64-bit result in vlo. */
> +	vlo |= (vhi << 32);
> +
> +	ret = sysfs_emit(buf, "%llu\n", vlo);
Is sysfs_emit now being used in place of scnprintf ? Is there a reason 
for the switch ?
> +
> +	return ret;
> +}
> +
> +static ssize_t
> +i915_power1_max_enable_show(struct device *dev, struct device_attribute *attr,
> +			    char *buf)
> +{
> +	struct drm_i915_private *i915 = dev_get_drvdata(dev);
> +	struct intel_uncore *uncore = &i915->uncore;
> +	intel_wakeref_t wakeref;
> +	ssize_t ret;
> +	u32 reg_value;
> +	bool is_enabled;
> +
> +	with_intel_runtime_pm(uncore->rpm, wakeref)
> +		reg_value = intel_uncore_read(uncore,
> +					      i915->hwmon.rg.pkg_rapl_limit);
> +
> +	is_enabled = !!(reg_value & PKG_PWR_LIM_1_EN);
> +
> +	ret = sysfs_emit(buf, "%u\n", is_enabled);
> +
> +	return ret;
> +}
> +
> +static ssize_t
> +i915_power1_max_interval_show(struct device *dev, struct device_attribute *attr,
> +			      char *buf)
> +{
> +	struct drm_i915_private *i915 = dev_get_drvdata(dev);
> +	struct intel_uncore *uncore = &i915->uncore;
> +	struct i915_hwmon *hwmon = &i915->hwmon;
> +	ssize_t ret;
> +	u64 ullval;
> +
> +	ullval = _field_read_and_scale(uncore, hwmon->rg.pkg_rapl_limit,
> +				       PKG_PWR_LIM_1_TIME,
> +				       FIELD_SHIFT(PKG_PWR_LIM_1_TIME),
> +				       hwmon->scl_shift_time, SF_TIME);
> +
> +	ret = sysfs_emit(buf, "%llu\n", ullval);
> +
> +	return ret;
> +}
> +
> +static ssize_t
> +i915_power1_max_interval_store(struct device *dev,
> +			       struct device_attribute *attr,
> +			       const char *buf, size_t count)
> +{
> +	struct drm_i915_private *i915 = dev_get_drvdata(dev);
> +	struct intel_uncore *uncore = &i915->uncore;
> +	struct i915_hwmon *hwmon = &i915->hwmon;
> +	ssize_t ret;
> +	long val;
> +
> +	ret = kstrtoul(buf, 0, &val);
> +	if (ret)
> +		return ret;
> +
> +	_field_scale_and_write(uncore, hwmon->rg.pkg_rapl_limit,
> +			       PKG_PWR_LIM_2_TIME,
> +			       FIELD_SHIFT(PKG_PWR_LIM_2_TIME),
> +			       hwmon->scl_shift_time, SF_TIME, val);
> +
> +	return count;
> +}
> +
> +static ssize_t
> +i915_power1_cap_enable_show(struct device *dev, struct device_attribute *attr,
> +			    char *buf)
> +{
> +	struct drm_i915_private *i915 = dev_get_drvdata(dev);
> +	struct intel_uncore *uncore = &i915->uncore;
> +	struct i915_hwmon *hwmon = &i915->hwmon;
> +	intel_wakeref_t wakeref;
> +	ssize_t ret;
> +	u32 reg_value;
> +	bool is_enabled;
> +
> +	with_intel_runtime_pm(uncore->rpm, wakeref)
> +		reg_value = intel_uncore_read(uncore,
> +					      hwmon->rg.pkg_rapl_limit_udw);
> +
> +	is_enabled = !!(reg_value & PKG_PWR_LIM_2_EN);
> +
> +	ret = sysfs_emit(buf, "%u\n", is_enabled);
> +
> +	return ret;
> +}
> +
> +static ssize_t
> +i915_power1_cap_enable_store(struct device *dev, struct device_attribute *attr,
> +			     const char *buf, size_t count)
> +{
> +	struct drm_i915_private *i915 = dev_get_drvdata(dev);
> +	struct intel_uncore *uncore = &i915->uncore;
> +	struct i915_hwmon *hwmon = &i915->hwmon;
> +	ssize_t ret;
> +	u32 val;
> +	u32 bits_to_clear;
> +	u32 bits_to_set;
> +
> +	ret = kstrtou32(buf, 0, &val);
> +	if (ret)
> +		return ret;
> +
> +	bits_to_clear = PKG_PWR_LIM_2_EN;
> +	if (!val)
> +		bits_to_set = 0;
> +	else
> +		bits_to_set = PKG_PWR_LIM_2_EN;
> +
> +	_locked_with_pm_intel_uncore_rmw(uncore, hwmon->rg.pkg_rapl_limit_udw,
> +					 bits_to_clear, bits_to_set);
> +
> +	return count;
> +}
> +
> +static ssize_t
> +i915_power_default_limit_show(struct device *dev, struct device_attribute *attr,
> +			      char *buf)
> +{
> +	struct drm_i915_private *i915 = dev_get_drvdata(dev);
> +	struct i915_hwmon *hwmon = &i915->hwmon;
> +	ssize_t ret;
> +
> +	ret = sysfs_emit(buf, "%u\n", hwmon->power_max_initial_value);
> +
> +	return ret;
> +}
> +
> +static ssize_t
> +i915_power_min_limit_show(struct device *dev, struct device_attribute *attr,
> +			  char *buf)
> +{
> +	struct drm_i915_private *i915 = dev_get_drvdata(dev);
> +	struct intel_uncore *uncore = &i915->uncore;
> +	struct i915_hwmon *hwmon = &i915->hwmon;
> +	ssize_t ret;
> +	u32 uval;
> +
> +	/*
> +	 * This is a 64-bit register but the individual fields are under 32 bits
> +	 * in size even after scaling.
> +	 * The UAPI specifies a size of 32 bits.
> +	 * The UAPI specifies that 0 should be returned if unsupported.
> +	 * So, using u32 and %u is sufficient.
> +	 */
> +	if (i915_mmio_reg_valid(hwmon->rg.pkg_power_sku))
> +		uval = (u32)_field_read64_and_scale(uncore,
> +						    hwmon->rg.pkg_power_sku,
> +						    PKG_MIN_PWR,
> +						    FIELD_SHIFT(PKG_MIN_PWR),
> +						    hwmon->scl_shift_power,
> +						    SF_POWER);
> +	else
> +		uval = 0;
> +
> +	ret = sysfs_emit(buf, "%u\n", uval);
> +
> +	return ret;
> +}
> +
> +static ssize_t
> +i915_power_max_limit_show(struct device *dev, struct device_attribute *attr,
> +			  char *buf)
> +{
> +	struct drm_i915_private *i915 = dev_get_drvdata(dev);
> +	struct intel_uncore *uncore = &i915->uncore;
> +	struct i915_hwmon *hwmon = &i915->hwmon;
> +	ssize_t ret;
> +	u32 uval;
> +
> +	/*
> +	 * This is a 64-bit register but the individual fields are under 32 bits
> +	 * in size even after scaling.
> +	 * The UAPI specifies a size of 32 bits.
> +	 * The UAPI specifies that UINT_MAX should be returned if unsupported.
> +	 * So, using u32 and %u is sufficient.
> +	 */
> +	if (i915_mmio_reg_valid(hwmon->rg.pkg_power_sku))
> +		uval = (u32)_field_read64_and_scale(uncore,
> +						    hwmon->rg.pkg_power_sku,
> +						    PKG_MAX_PWR,
> +						    FIELD_SHIFT(PKG_MAX_PWR),
> +						    hwmon->scl_shift_power,
> +						    SF_POWER);
> +	else
> +		uval = UINT_MAX;
> +
> +	ret = sysfs_emit(buf, "%u\n", uval);
> +
> +	return ret;
> +}
> +
> +static SENSOR_DEVICE_ATTR(power1_max_enable, 0444,
> +			  i915_power1_max_enable_show, NULL, 0);
> +static SENSOR_DEVICE_ATTR(power1_max_interval, 0664,
> +			  i915_power1_max_interval_show,
> +			  i915_power1_max_interval_store, 0);
> +static SENSOR_DEVICE_ATTR(power1_cap_enable, 0664,
> +			  i915_power1_cap_enable_show,
> +			  i915_power1_cap_enable_store, 0);
> +static SENSOR_DEVICE_ATTR(power_default_limit, 0444,
> +			  i915_power_default_limit_show, NULL, 0);
> +static SENSOR_DEVICE_ATTR(power_min_limit, 0444,
> +			  i915_power_min_limit_show, NULL, 0);
> +static SENSOR_DEVICE_ATTR(power_max_limit, 0444,
> +			  i915_power_max_limit_show, NULL, 0);
> +static SENSOR_DEVICE_ATTR(energy1_input, 0444,
> +			  i915_energy1_input_show, NULL, 0);
> +
> +static struct attribute *hwmon_attributes[] = {
> +	&sensor_dev_attr_power1_max_enable.dev_attr.attr,
> +	&sensor_dev_attr_power1_max_interval.dev_attr.attr,
> +	&sensor_dev_attr_power1_cap_enable.dev_attr.attr,
> +	&sensor_dev_attr_power_default_limit.dev_attr.attr,
> +	&sensor_dev_attr_power_min_limit.dev_attr.attr,
> +	&sensor_dev_attr_power_max_limit.dev_attr.attr,
> +	&sensor_dev_attr_energy1_input.dev_attr.attr,
> +	NULL
> +};
> +
> +static umode_t hwmon_attributes_visible(struct kobject *kobj,
> +					struct attribute *attr, int index)
> +{
> +	struct device *dev = kobj_to_dev(kobj);
> +	struct drm_i915_private *i915 = dev_get_drvdata(dev);
> +	struct i915_hwmon *hwmon = &i915->hwmon;
> +	i915_reg_t rgadr;
> +
> +	if (attr == &sensor_dev_attr_energy1_input.dev_attr.attr)
> +		rgadr = hwmon->rg.pkg_energy_status;
> +	else if (attr == &sensor_dev_attr_power1_max_enable.dev_attr.attr)
> +		rgadr = hwmon->rg.pkg_rapl_limit;
> +	else if (attr == &sensor_dev_attr_power1_max_interval.dev_attr.attr)
> +		rgadr = hwmon->rg.pkg_rapl_limit;
> +	else if (attr == &sensor_dev_attr_power1_cap_enable.dev_attr.attr)
> +		rgadr = hwmon->rg.pkg_rapl_limit_udw;
> +	else if (attr == &sensor_dev_attr_power_default_limit.dev_attr.attr)
> +		rgadr = hwmon->rg.pkg_rapl_limit;
> +	else if (attr == &sensor_dev_attr_power_min_limit.dev_attr.attr)
> +		return attr->mode;
> +	else if (attr == &sensor_dev_attr_power_max_limit.dev_attr.attr)
> +		return attr->mode;
> +	else
> +		return 0;
> +
> +	if (!i915_mmio_reg_valid(rgadr))
> +		return 0;
> +
> +	return attr->mode;
> +}
> +
> +static const struct attribute_group hwmon_attrgroup = {
> +	.attrs = hwmon_attributes,
> +	.is_visible = hwmon_attributes_visible,
> +};
> +
> +static const struct attribute_group *hwmon_groups[] = {
> +	&hwmon_attrgroup,
> +	NULL
> +};
> +
> +/*
> + * HWMON SENSOR TYPE = hwmon_power
> + *  - Sustained Power (power1_max)
> + *  - Burst power     (power1_cap)
> + *  - Peak power      (power1_crit)
> + */
> +static const u32 i915_config_power[] = {
> +	HWMON_P_CAP | HWMON_P_MAX,
> +	0
> +};
> +
> +static const struct hwmon_channel_info i915_power = {
> +	.type = hwmon_power,
> +	.config = i915_config_power,
> +};
> +
> +static const struct hwmon_channel_info *i915_info[] = {
> +	&i915_power,
> +	NULL
> +};
> +
> +static umode_t
> +i915_power_is_visible(const struct drm_i915_private *i915, u32 attr, int chan)
> +{
> +	i915_reg_t rgadr;
> +
> +	switch (attr) {
> +	case hwmon_power_max:
> +		rgadr = i915->hwmon.rg.pkg_rapl_limit;
> +		break;
> +	case hwmon_power_cap:
> +		rgadr = i915->hwmon.rg.pkg_rapl_limit_udw;
> +		break;
> +	default:
> +		return 0;
> +	}
> +
> +	if (!i915_mmio_reg_valid(rgadr))
> +		return 0;
> +
> +	return 0664;
> +}
> +
> +static int
> +i915_power_read(struct drm_i915_private *i915, u32 attr, int chan, long *val)
> +{
> +	struct intel_uncore *uncore = &i915->uncore;
> +	struct i915_hwmon *hwmon = &i915->hwmon;
> +	int ret = 0;
> +
> +	switch (attr) {
> +	case hwmon_power_max:
> +		*val = (long)_field_read_and_scale(uncore,
> +						   hwmon->rg.pkg_rapl_limit,
> +						   PKG_PWR_LIM_1,
> +						   FIELD_SHIFT(PKG_PWR_LIM_1),
> +						   hwmon->scl_shift_power,
> +						   SF_POWER);
> +		break;
> +	case hwmon_power_cap:
> +		*val = (long)_field_read_and_scale(uncore,
> +						   hwmon->rg.pkg_rapl_limit_udw,
> +						   PKG_PWR_LIM_2,
> +						   FIELD_SHIFT(PKG_PWR_LIM_2),
> +						   hwmon->scl_shift_power,
> +						   SF_POWER);
> +		break;
> +	default:
> +		ret = -EOPNOTSUPP;
> +	}
> +
> +	return ret;
> +}
> +
> +static int
> +i915_power_write(struct drm_i915_private *i915, u32 attr, int chan, long val)
> +{
> +	struct intel_uncore *uncore = &i915->uncore;
> +	struct i915_hwmon *hwmon = &i915->hwmon;
> +	int ret = 0;
> +
> +	switch (attr) {
> +	case hwmon_power_max:
> +		_field_scale_and_write(uncore,
> +				       hwmon->rg.pkg_rapl_limit,
> +				       PKG_PWR_LIM_1,
> +				       FIELD_SHIFT(PKG_PWR_LIM_1),
> +				       hwmon->scl_shift_power,
> +				       SF_POWER, val);
> +		break;
> +	case hwmon_power_cap:
> +		_field_scale_and_write(uncore,
> +				       hwmon->rg.pkg_rapl_limit_udw,
> +				       PKG_PWR_LIM_2,
> +				       FIELD_SHIFT(PKG_PWR_LIM_2),
> +				       hwmon->scl_shift_power,
> +				       SF_POWER, val);
> +		break;
> +	default:
> +		ret = -EOPNOTSUPP;
> +	}
> +
> +	return ret;
> +}
> +
> +static umode_t
> +i915_is_visible(const void *data, enum hwmon_sensor_types type,
> +		u32 attr, int channel)
> +{
> +	struct drm_i915_private *i915 = (struct drm_i915_private *)data;
> +
> +	switch (type) {
> +	case hwmon_power:
> +		return i915_power_is_visible(i915, attr, channel);
> +	default:
> +		return 0;
> +	}
> +}
> +
> +static int
> +i915_read(struct device *dev, enum hwmon_sensor_types type, u32 attr,
> +	  int channel, long *val)
> +{
> +	struct drm_i915_private *i915 = kdev_to_i915(dev);
> +
> +	switch (type) {
> +	case hwmon_power:
> +		return i915_power_read(i915, attr, channel, val);
> +	default:
> +		return -EOPNOTSUPP;
> +	}
> +}
> +
> +static int
> +i915_write(struct device *dev, enum hwmon_sensor_types type, u32 attr,
> +	   int channel, long val)
> +{
> +	struct drm_i915_private *i915 = kdev_to_i915(dev);
> +
> +	switch (type) {
> +	case hwmon_power:
> +		return i915_power_write(i915, attr, channel, val);
> +	default:
> +		return -EOPNOTSUPP;
> +	}
> +}
> +
> +static const struct hwmon_ops i915_hwmon_ops = {
> +	.is_visible = i915_is_visible,
> +	.read = i915_read,
> +	.write = i915_write,
> +};
> +
> +static const struct hwmon_chip_info i915_chip_info = {
> +	.ops = &i915_hwmon_ops,
> +	.info = i915_info,
> +};
> +
> +static void
> +i915_hwmon_get_preregistration_info(struct drm_i915_private *i915)
> +{
> +	struct i915_hwmon *hwmon = &i915->hwmon;
> +	struct intel_uncore *uncore = &i915->uncore;
> +	intel_wakeref_t wakeref;
> +	u32 val_sku_unit;
> +	__le32 le_sku_unit;
> +
> +	if (IS_DG1(i915)) {
> +		hwmon->rg.pkg_power_sku_unit = PCU_PACKAGE_POWER_SKU_UNIT;
> +		hwmon->rg.pkg_power_sku = PCU_PACKAGE_POWER_SKU;
> +		hwmon->rg.pkg_energy_status = PCU_PACKAGE_ENERGY_STATUS;
> +		hwmon->rg.pkg_rapl_limit = PCU_PACKAGE_RAPL_LIMIT;
> +		hwmon->rg.pkg_rapl_limit_udw = PCU_PACKAGE_RAPL_LIMIT_UDW;
> +	} else {
> +		hwmon->rg.pkg_power_sku_unit = INVALID_MMIO_REG;
> +		hwmon->rg.pkg_power_sku = INVALID_MMIO_REG;
> +		hwmon->rg.pkg_energy_status = INVALID_MMIO_REG;
> +		hwmon->rg.pkg_rapl_limit = INVALID_MMIO_REG;
> +		hwmon->rg.pkg_rapl_limit_udw = INVALID_MMIO_REG;
> +	}
> +
> +	wakeref = intel_runtime_pm_get(uncore->rpm);
> +
> +	/*
> +	 * The contents of register hwmon->rg.pkg_power_sku_unit do not change,
> +	 * so read it once and store the shift values.
> +	 */
> +	if (i915_mmio_reg_valid(hwmon->rg.pkg_power_sku_unit))
> +		val_sku_unit = intel_uncore_read(uncore,
> +						 hwmon->rg.pkg_power_sku_unit);
> +	else
> +		val_sku_unit = 0;
> +
> +	hwmon->energy_counter_overflow = 0;
> +
> +	if (i915_mmio_reg_valid(hwmon->rg.pkg_energy_status))
> +		hwmon->energy_counter_prev =
> +			intel_uncore_read(uncore, hwmon->rg.pkg_energy_status);
> +	else
> +		hwmon->energy_counter_prev = 0;
> +
> +	intel_runtime_pm_put(uncore->rpm, wakeref);
> +
> +	le_sku_unit = cpu_to_le32(val_sku_unit);
> +	hwmon->scl_shift_power = le32_get_bits(le_sku_unit, PKG_PWR_UNIT);
> +	hwmon->scl_shift_energy = le32_get_bits(le_sku_unit, PKG_ENERGY_UNIT);
> +	hwmon->scl_shift_time = le32_get_bits(le_sku_unit, PKG_TIME_UNIT);
> +
> +	/*
> +	 * There is no direct way to obtain the power default_limit.
> +	 * The best known workaround is to use the initial value of power1_max.
> +	 *
> +	 * The value of power1_max is reset to the default on reboot, but is
> +	 * not reset by a module unload/load sequence.  To allow proper
> +	 * functioning after a module reload, the value for power1_max is
> +	 * restored to its original value at module unload time in
> +	 * i915_hwmon_unregister().
> +	 */
> +	hwmon->power_max_initial_value =
> +		(u32)_field_read_and_scale(uncore,
> +					   hwmon->rg.pkg_rapl_limit,
> +					   PKG_PWR_LIM_1,
> +					   FIELD_SHIFT(PKG_PWR_LIM_1),
> +					   hwmon->scl_shift_power, SF_POWER);
> +}
> +
> +void i915_hwmon_register(struct drm_i915_private *i915)
> +{
> +	struct drm_device *drm_dev = &i915->drm;
> +	struct i915_hwmon *hwmon = &i915->hwmon;
> +	struct device *hwmon_dev;
> +
> +	mutex_init(&hwmon->hwmon_lock);
> +
> +	i915_hwmon_get_preregistration_info(i915);
> +
> +	hwmon_dev = hwmon_device_register_with_info(drm_dev->dev, "i915",
> +						    drm_dev,
> +						    &i915_chip_info,
> +						    hwmon_groups);
> +
> +	if (IS_ERR(hwmon_dev)) {
> +		mutex_destroy(&hwmon->hwmon_lock);
> +		drm_info(&i915->drm, "Failed to register hwmon for i915\n");
> +		return;
> +	}
> +
> +	hwmon->dev = hwmon_dev;
> +}
> +
> +void i915_hwmon_unregister(struct drm_i915_private *i915)
> +{
> +	struct i915_hwmon *hwmon = &i915->hwmon;
> +
> +	if (hwmon->power_max_initial_value) {
> +		/* Restore power1_max. */
> +		_field_scale_and_write(&i915->uncore, hwmon->rg.pkg_rapl_limit,
> +				       PKG_PWR_LIM_1,
> +				       FIELD_SHIFT(PKG_PWR_LIM_1),
> +				       hwmon->scl_shift_power,
> +				       SF_POWER,
> +				       hwmon->power_max_initial_value);
> +	}
> +
> +	if (hwmon->dev)
> +		hwmon_device_unregister(hwmon->dev);
> +
> +	mutex_destroy(&hwmon->hwmon_lock);
> +
> +	memset(hwmon, 0, sizeof(*hwmon));
> +}
> diff --git a/drivers/gpu/drm/i915/i915_hwmon.h b/drivers/gpu/drm/i915/i915_hwmon.h
> new file mode 100644
> index 0000000000000..2fff4f9a6303f
> --- /dev/null
> +++ b/drivers/gpu/drm/i915/i915_hwmon.h
> @@ -0,0 +1,42 @@
> +/* SPDX-License-Identifier: MIT */
> +
> +/*
> + * Copyright © 2020 Intel Corporation
> + */
> +
> +#ifndef __INTEL_HWMON_H__
> +#define __INTEL_HWMON_H__
> +
> +#include <linux/types.h>
> +#include <linux/mutex.h>
> +#include "i915_reg.h"
> +
> +struct i915_hwmon_reg {
> +	i915_reg_t pkg_power_sku_unit;
> +	i915_reg_t pkg_power_sku;
> +	i915_reg_t pkg_energy_status;
> +	i915_reg_t pkg_rapl_limit;
> +	i915_reg_t pkg_rapl_limit_udw;
> +};
> +
> +struct i915_hwmon {
> +	struct device *dev;
> +	struct mutex hwmon_lock;	/* counter overflow logic and rmw */
> +
> +	struct i915_hwmon_reg rg;
> +
> +	u32 energy_counter_overflow;
> +	u32 energy_counter_prev;
> +	u32 power_max_initial_value;
> +
> +	int scl_shift_power;
> +	int scl_shift_energy;
> +	int scl_shift_time;
> +};
> +
> +struct drm_i915_private;
> +
> +void i915_hwmon_register(struct drm_i915_private *i915);
> +void i915_hwmon_unregister(struct drm_i915_private *i915);
> +
> +#endif
> diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
> index 4979b4965a828..931fdd3a681ac 100644
> --- a/drivers/gpu/drm/i915/i915_reg.h
> +++ b/drivers/gpu/drm/i915/i915_reg.h
> @@ -4083,6 +4083,58 @@ static inline bool i915_mmio_reg_valid(i915_reg_t reg)
>   #define BXT_RP_STATE_CAP        _MMIO(0x138170)
>   #define GEN9_RP_STATE_LIMITS	_MMIO(0x138148)
>   
> +/* DG1 */
> +
> +/* based on MCHBAR_MIRROR_BASE_SNB == 0x140000 */
> +#define PCU_PACKAGE_POWER_SKU_UNIT	_MMIO(MCHBAR_MIRROR_BASE_SNB + 0x5938)
> +#define PCU_PACKAGE_ENERGY_STATUS	_MMIO(MCHBAR_MIRROR_BASE_SNB + 0x593c)
> +#define PCU_PACKAGE_RAPL_LIMIT		_MMIO(MCHBAR_MIRROR_BASE_SNB + 0x59a0)
> +#define PCU_PACKAGE_RAPL_LIMIT_UDW	_MMIO(MCHBAR_MIRROR_BASE_SNB + 0x59a4)
> +#define PCU_PACKAGE_POWER_SKU		INVALID_MMIO_REG
> +
> +/* Fields for *_PACKAGE_RAPL_LIMIT: */
> +#define   PKG_PWR_LIM_1			REG_GENMASK(14, 0)
> +#define   PKG_PWR_LIM_1_EN		REG_BIT(15)
> +#define   PKG_PWR_LIM_1_TIME		REG_GENMASK(23, 17)
> +
> +/*
> + * Fields for *_PACKAGE_RAPL_LIMIT_UDW:
> + * In docs, these fields may be defined relative to the entire 64-bit
> + * register, but here they are defined relative to the 32-bit boundary.
> + */
> +#define   PKG_PWR_LIM_2			REG_GENMASK(14, 0)	// 46:32
> +#define   PKG_PWR_LIM_2_EN		REG_BIT(15)		// 47:47
> +#define   PKG_PWR_LIM_2_TIME		REG_GENMASK(23, 17)	// 55:49
> +
> +/*
> + * *_PACKAGE_POWER_SKU_UNIT - fields specifying scaling for PCU quantities.
> + * - PKG_PWR_UNIT - Power Units used for power control registers. The
> + *   actual unit value is calculated by 1 W / Power(2,PKG_PWR_UNIT).
> + * - PKG_ENERGY_UNIT - Energy Units used for power control registers. The
> + *   actual unit value is calculated by 1 J / Power(2,PKG_ENERGY_UNIT).
> + * - PKG_TIME_UNIT - Time Units used for power control registers. The
> + *   actual unit value is calculated by 1 s / Power(2,PKG_TIME_UNIT).
> + */
> +#define   PKG_PWR_UNIT			REG_GENMASK(3, 0)
> +#define   PKG_ENERGY_UNIT		REG_GENMASK(12, 8)
> +#define   PKG_TIME_UNIT			REG_GENMASK(19, 16)
> +
> +/*
> + * *_PACKAGE_POWER_SKU - SKU power and timing parameters.
> + * Used herein as a 64-bit bit register.
> + * These masks are defined using GENMASK_ULL as REG_GENMASK is limited to u32
> + * and as GENMASK is "long" and therefore 32-bits on a 32-bit system.
> + * PKG_PKG_TDP, PKG_MIN_PWR, and PKG_MAX_PWR are scaled in the same way as
> + * PKG_PWR_LIM_*, above.
> + * PKG_MAX_WIN has sub-fields for x and y, and has the value: is 1.x * 2^y.
> + */
> +#define   PKG_PKG_TDP			GENMASK_ULL(14, 0)
> +#define   PKG_MIN_PWR			GENMASK_ULL(30, 16)
> +#define   PKG_MAX_PWR			GENMASK_ULL(46, 32)
> +#define   PKG_MAX_WIN			GENMASK_ULL(54, 48)
> +#define     PKG_MAX_WIN_Y		GENMASK_ULL(54, 53)
> +#define     PKG_MAX_WIN_X		GENMASK_ULL(52, 48)
> +
>   /*
>    * Logical Context regs
>    */