diff mbox series

[6/7] drm/i915/hwmon: Expose power1_max_interval

Message ID 20220812173715.2398586-7-badal.nilawar@intel.com (mailing list archive)
State Handled Elsewhere
Headers show
Series drm/i915: Add HWMON support | expand

Commit Message

Nilawar, Badal Aug. 12, 2022, 5:37 p.m. UTC
From: Ashutosh Dixit <ashutosh.dixit@intel.com>

Expose power1_max_interval, that is the tau corresponding to PL1. Some bit
manipulation is needed because of the format of PKG_PWR_LIM_1_TIME in
GT0_PACKAGE_RAPL_LIMIT register (1.x * power(2,y)).

v2: Update date and kernel version in Documentation (Badal)

Signed-off-by: Ashutosh Dixit <ashutosh.dixit@intel.com>
Signed-off-by: Badal Nilawar <badal.nilawar@intel.com>
---
 .../ABI/testing/sysfs-driver-intel-i915-hwmon |   9 ++
 drivers/gpu/drm/i915/i915_hwmon.c             | 128 +++++++++++++++++-
 drivers/gpu/drm/i915/i915_reg.h               |   4 +-
 drivers/gpu/drm/i915/intel_mchbar_regs.h      |   4 +
 4 files changed, 142 insertions(+), 3 deletions(-)

Comments

Guenter Roeck Aug. 12, 2022, 6:10 p.m. UTC | #1
On 8/12/22 10:37, Badal Nilawar wrote:
> From: Ashutosh Dixit <ashutosh.dixit@intel.com>
> 
> Expose power1_max_interval, that is the tau corresponding to PL1. Some bit
> manipulation is needed because of the format of PKG_PWR_LIM_1_TIME in
> GT0_PACKAGE_RAPL_LIMIT register (1.x * power(2,y)).
> 
> v2: Update date and kernel version in Documentation (Badal)
> 
> Signed-off-by: Ashutosh Dixit <ashutosh.dixit@intel.com>
> Signed-off-by: Badal Nilawar <badal.nilawar@intel.com>

Acked-by: Guenter Roeck <linux@roeck-us.net>

> ---
>   .../ABI/testing/sysfs-driver-intel-i915-hwmon |   9 ++
>   drivers/gpu/drm/i915/i915_hwmon.c             | 128 +++++++++++++++++-
>   drivers/gpu/drm/i915/i915_reg.h               |   4 +-
>   drivers/gpu/drm/i915/intel_mchbar_regs.h      |   4 +
>   4 files changed, 142 insertions(+), 3 deletions(-)
> 
> diff --git a/Documentation/ABI/testing/sysfs-driver-intel-i915-hwmon b/Documentation/ABI/testing/sysfs-driver-intel-i915-hwmon
> index bb1101757154..34668f6c2dc4 100644
> --- a/Documentation/ABI/testing/sysfs-driver-intel-i915-hwmon
> +++ b/Documentation/ABI/testing/sysfs-driver-intel-i915-hwmon
> @@ -26,6 +26,15 @@ Description:	RO. Card default power limit (default TDP setting).
>   
>   		Only supported for particular Intel i915 graphics platforms.
>   
> +What:		/sys/devices/.../hwmon/hwmon<i>/power1_max_interval
> +Date:		June 2022
> +KernelVersion:	5.19
> +Contact:	dri-devel@lists.freedesktop.org
> +Description:	RW. Sustained power limit interval (Tau in PL1/Tau) in
> +		milliseconds over which sustained power is averaged.
> +
> +		Only supported for particular Intel i915 graphics platforms.
> +
>   What:		/sys/devices/.../hwmon/hwmon<i>/power1_crit
>   Date:		June 2022
>   KernelVersion:	5.19
> diff --git a/drivers/gpu/drm/i915/i915_hwmon.c b/drivers/gpu/drm/i915/i915_hwmon.c
> index b1a89a6aa220..6760133c7905 100644
> --- a/drivers/gpu/drm/i915/i915_hwmon.c
> +++ b/drivers/gpu/drm/i915/i915_hwmon.c
> @@ -15,10 +15,12 @@
>   
>   /*
>    * SF_* - scale factors for particular quantities according to hwmon spec.
> + * - time   - milliseconds
>    * - power  - microwatts
>    * - curr   - milliamperes
>    * - energy - microjoules
>    */
> +#define SF_TIME            1000
>   #define SF_POWER	1000000
>   #define SF_CURR		1000
>   #define SF_ENERGY	1000000
> @@ -56,6 +58,7 @@ struct i915_hwmon {
>   	u32 power_max_initial_value;
>   	int scl_shift_power;
>   	int scl_shift_energy;
> +	int scl_shift_time;
>   };
>   
>   static void
> @@ -177,6 +180,128 @@ i915_hwmon_energy_status_get(struct drm_i915_private *i915, long *energy)
>   	return hwm_energy(ddat, energy);
>   }
>   
> +static ssize_t
> +hwm_power1_max_interval_show(struct device *dev, struct device_attribute *attr,
> +			     char *buf)
> +{
> +	struct hwm_drvdata *ddat = dev_get_drvdata(dev);
> +	struct i915_hwmon *hwmon = ddat->hwmon;
> +	intel_wakeref_t wakeref;
> +	u32 r, x, y, x_w = 2; /* 2 bits */
> +	u64 tau4, out;
> +
> +	with_intel_runtime_pm(ddat->uncore->rpm, wakeref)
> +		r = intel_uncore_read(ddat->uncore, hwmon->rg.pkg_rapl_limit);
> +
> +	x = REG_FIELD_GET(PKG_PWR_LIM_1_TIME_X, r);
> +	y = REG_FIELD_GET(PKG_PWR_LIM_1_TIME_Y, r);
> +	/*
> +	 * tau = 1.x * power(2,y), x = bits(23:22), y = bits(21:17)
> +	 *     = (4 | x) << (y - 2)
> +	 * where (y - 2) ensures a 1.x fixed point representation of 1.x
> +	 * However because y can be < 2, we compute
> +	 *     tau4 = (4 | x) << y
> +	 * but add 2 when doing the final right shift to account for units
> +	 */
> +	tau4 = ((1 << x_w) | x) << y;
> +	/* val in hwmon interface units (millisec) */
> +	out = mul_u64_u32_shr(tau4, SF_TIME, hwmon->scl_shift_time + x_w);
> +
> +	return sysfs_emit(buf, "%llu\n", out);
> +}
> +
> +static ssize_t
> +hwm_power1_max_interval_store(struct device *dev,
> +			      struct device_attribute *attr,
> +			      const char *buf, size_t count)
> +{
> +	struct hwm_drvdata *ddat = dev_get_drvdata(dev);
> +	struct i915_hwmon *hwmon = ddat->hwmon;
> +	long val, max_win, ret;
> +	u32 x, y, rxy, x_w = 2; /* 2 bits */
> +	intel_wakeref_t wakeref;
> +	u64 tau4, r;
> +
> +#define PKG_MAX_WIN_DEFAULT 0x12ull
> +
> +	ret = kstrtoul(buf, 0, &val);
> +	if (ret)
> +		return ret;
> +
> +	/* val must be < max in hwmon interface units */
> +	if (i915_mmio_reg_valid(hwmon->rg.pkg_power_sku)) {
> +		with_intel_runtime_pm(ddat->uncore->rpm, wakeref)
> +			r = intel_uncore_read64(ddat->uncore, hwmon->rg.pkg_power_sku);
> +		/*
> +		 * FIXME
> +		 * Wa_22015381490:pvc rg.pkg_power_sku value is incorrect on PVC
> +		 * at least. The following seems to work:
> +		 *	r <<= 8;
> +		 * However for now to be safe just use the default value
> +		 * below. Once issue is resolved remove the one line below.
> +		 */
> +		r = FIELD_PREP(PKG_MAX_WIN, PKG_MAX_WIN_DEFAULT);
> +	} else {
> +		r = FIELD_PREP(PKG_MAX_WIN, PKG_MAX_WIN_DEFAULT);
> +	}
> +
> +	/* Steps below are explained in i915_power1_max_interval_show() */
> +	x = REG_FIELD_GET(PKG_MAX_WIN_X, r);
> +	y = REG_FIELD_GET(PKG_MAX_WIN_Y, r);
> +	tau4 = ((1 << x_w) | x) << y;
> +	max_win = mul_u64_u32_shr(tau4, SF_TIME, hwmon->scl_shift_time + x_w);
> +
> +	if (val > max_win)
> +		return -EINVAL;
> +
> +	/* val in hw units */
> +	val = DIV_ROUND_CLOSEST_ULL((u64)val << hwmon->scl_shift_time, SF_TIME);
> +	/* Convert to 1.x * power(2,y) */
> +	if (!val)
> +		return -EINVAL;
> +	y = ilog2(val);
> +	/* x = (val - (1 << y)) >> (y - 2); */
> +	x = (val - (1ul << y)) << x_w >> y;
> +
> +	rxy = REG_FIELD_PREP(PKG_PWR_LIM_1_TIME_X, x) | REG_FIELD_PREP(PKG_PWR_LIM_1_TIME_Y, y);
> +
> +	hwm_locked_with_pm_intel_uncore_rmw(ddat, hwmon->rg.pkg_rapl_limit,
> +					    PKG_PWR_LIM_1_TIME, rxy);
> +	return count;
> +}
> +
> +static SENSOR_DEVICE_ATTR(power1_max_interval, 0664,
> +			  hwm_power1_max_interval_show,
> +			  hwm_power1_max_interval_store, 0);
> +
> +static struct attribute *hwm_attributes[] = {
> +	&sensor_dev_attr_power1_max_interval.dev_attr.attr,
> +	NULL
> +};
> +
> +static umode_t hwm_attributes_visible(struct kobject *kobj,
> +				      struct attribute *attr, int index)
> +{
> +	struct device *dev = kobj_to_dev(kobj);
> +	struct hwm_drvdata *ddat = dev_get_drvdata(dev);
> +	struct i915_hwmon *hwmon = ddat->hwmon;
> +
> +	if (attr == &sensor_dev_attr_power1_max_interval.dev_attr.attr)
> +		return i915_mmio_reg_valid(hwmon->rg.pkg_rapl_limit) ? attr->mode : 0;
> +	else
> +		return 0;
> +}
> +
> +static const struct attribute_group hwm_attrgroup = {
> +	.attrs = hwm_attributes,
> +	.is_visible = hwm_attributes_visible,
> +};
> +
> +static const struct attribute_group *hwm_groups[] = {
> +	&hwm_attrgroup,
> +	NULL
> +};
> +
>   static const struct hwmon_channel_info *hwm_info[] = {
>   	HWMON_CHANNEL_INFO(in, HWMON_I_INPUT),
>   	HWMON_CHANNEL_INFO(power, HWMON_P_MAX | HWMON_P_RATED_MAX | HWMON_P_CRIT),
> @@ -495,6 +620,7 @@ hwm_get_preregistration_info(struct drm_i915_private *i915)
>   
>   	hwmon->scl_shift_power = REG_FIELD_GET(PKG_PWR_UNIT, val_sku_unit);
>   	hwmon->scl_shift_energy = REG_FIELD_GET(PKG_ENERGY_UNIT, val_sku_unit);
> +	hwmon->scl_shift_time = REG_FIELD_GET(PKG_TIME_UNIT, val_sku_unit);
>   
>   	/*
>   	 * Initialize 'struct hwm_energy_info', i.e. set fields to the
> @@ -533,7 +659,7 @@ void i915_hwmon_register(struct drm_i915_private *i915)
>   	hwmon_dev = hwmon_device_register_with_info(dev, ddat->name,
>   						    ddat,
>   						    &hwm_chip_info,
> -						    NULL);
> +						    hwm_groups);
>   	if (IS_ERR(hwmon_dev)) {
>   		mutex_destroy(&hwmon->hwmon_lock);
>   		i915->hwmon = NULL;
> diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
> index 041b858b95f4..05db98252a2f 100644
> --- a/drivers/gpu/drm/i915/i915_reg.h
> +++ b/drivers/gpu/drm/i915/i915_reg.h
> @@ -1879,8 +1879,8 @@
>   #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)
> +#define     PKG_MAX_WIN_X		GENMASK_ULL(54, 53)
> +#define     PKG_MAX_WIN_Y		GENMASK_ULL(52, 48)
>   
>   #define CHV_CLK_CTL1			_MMIO(0x101100)
>   #define VLV_CLK_CTL2			_MMIO(0x101104)
> diff --git a/drivers/gpu/drm/i915/intel_mchbar_regs.h b/drivers/gpu/drm/i915/intel_mchbar_regs.h
> index 18fcfc39ca2f..930cb4d76bbb 100644
> --- a/drivers/gpu/drm/i915/intel_mchbar_regs.h
> +++ b/drivers/gpu/drm/i915/intel_mchbar_regs.h
> @@ -204,6 +204,10 @@
>   
>   #define PCU_PACKAGE_RAPL_LIMIT			_MMIO(MCHBAR_MIRROR_BASE_SNB + 0x59a0)
>   #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)
> +#define   PKG_PWR_LIM_1_TIME_X			REG_GENMASK(23, 22)
> +#define   PKG_PWR_LIM_1_TIME_Y			REG_GENMASK(21, 17)
>   
>   /* snb MCH registers for priority tuning */
>   #define MCH_SSKPD				_MMIO(MCHBAR_MIRROR_BASE_SNB + 0x5d10)
diff mbox series

Patch

diff --git a/Documentation/ABI/testing/sysfs-driver-intel-i915-hwmon b/Documentation/ABI/testing/sysfs-driver-intel-i915-hwmon
index bb1101757154..34668f6c2dc4 100644
--- a/Documentation/ABI/testing/sysfs-driver-intel-i915-hwmon
+++ b/Documentation/ABI/testing/sysfs-driver-intel-i915-hwmon
@@ -26,6 +26,15 @@  Description:	RO. Card default power limit (default TDP setting).
 
 		Only supported for particular Intel i915 graphics platforms.
 
+What:		/sys/devices/.../hwmon/hwmon<i>/power1_max_interval
+Date:		June 2022
+KernelVersion:	5.19
+Contact:	dri-devel@lists.freedesktop.org
+Description:	RW. Sustained power limit interval (Tau in PL1/Tau) in
+		milliseconds over which sustained power is averaged.
+
+		Only supported for particular Intel i915 graphics platforms.
+
 What:		/sys/devices/.../hwmon/hwmon<i>/power1_crit
 Date:		June 2022
 KernelVersion:	5.19
diff --git a/drivers/gpu/drm/i915/i915_hwmon.c b/drivers/gpu/drm/i915/i915_hwmon.c
index b1a89a6aa220..6760133c7905 100644
--- a/drivers/gpu/drm/i915/i915_hwmon.c
+++ b/drivers/gpu/drm/i915/i915_hwmon.c
@@ -15,10 +15,12 @@ 
 
 /*
  * SF_* - scale factors for particular quantities according to hwmon spec.
+ * - time   - milliseconds
  * - power  - microwatts
  * - curr   - milliamperes
  * - energy - microjoules
  */
+#define SF_TIME            1000
 #define SF_POWER	1000000
 #define SF_CURR		1000
 #define SF_ENERGY	1000000
@@ -56,6 +58,7 @@  struct i915_hwmon {
 	u32 power_max_initial_value;
 	int scl_shift_power;
 	int scl_shift_energy;
+	int scl_shift_time;
 };
 
 static void
@@ -177,6 +180,128 @@  i915_hwmon_energy_status_get(struct drm_i915_private *i915, long *energy)
 	return hwm_energy(ddat, energy);
 }
 
+static ssize_t
+hwm_power1_max_interval_show(struct device *dev, struct device_attribute *attr,
+			     char *buf)
+{
+	struct hwm_drvdata *ddat = dev_get_drvdata(dev);
+	struct i915_hwmon *hwmon = ddat->hwmon;
+	intel_wakeref_t wakeref;
+	u32 r, x, y, x_w = 2; /* 2 bits */
+	u64 tau4, out;
+
+	with_intel_runtime_pm(ddat->uncore->rpm, wakeref)
+		r = intel_uncore_read(ddat->uncore, hwmon->rg.pkg_rapl_limit);
+
+	x = REG_FIELD_GET(PKG_PWR_LIM_1_TIME_X, r);
+	y = REG_FIELD_GET(PKG_PWR_LIM_1_TIME_Y, r);
+	/*
+	 * tau = 1.x * power(2,y), x = bits(23:22), y = bits(21:17)
+	 *     = (4 | x) << (y - 2)
+	 * where (y - 2) ensures a 1.x fixed point representation of 1.x
+	 * However because y can be < 2, we compute
+	 *     tau4 = (4 | x) << y
+	 * but add 2 when doing the final right shift to account for units
+	 */
+	tau4 = ((1 << x_w) | x) << y;
+	/* val in hwmon interface units (millisec) */
+	out = mul_u64_u32_shr(tau4, SF_TIME, hwmon->scl_shift_time + x_w);
+
+	return sysfs_emit(buf, "%llu\n", out);
+}
+
+static ssize_t
+hwm_power1_max_interval_store(struct device *dev,
+			      struct device_attribute *attr,
+			      const char *buf, size_t count)
+{
+	struct hwm_drvdata *ddat = dev_get_drvdata(dev);
+	struct i915_hwmon *hwmon = ddat->hwmon;
+	long val, max_win, ret;
+	u32 x, y, rxy, x_w = 2; /* 2 bits */
+	intel_wakeref_t wakeref;
+	u64 tau4, r;
+
+#define PKG_MAX_WIN_DEFAULT 0x12ull
+
+	ret = kstrtoul(buf, 0, &val);
+	if (ret)
+		return ret;
+
+	/* val must be < max in hwmon interface units */
+	if (i915_mmio_reg_valid(hwmon->rg.pkg_power_sku)) {
+		with_intel_runtime_pm(ddat->uncore->rpm, wakeref)
+			r = intel_uncore_read64(ddat->uncore, hwmon->rg.pkg_power_sku);
+		/*
+		 * FIXME
+		 * Wa_22015381490:pvc rg.pkg_power_sku value is incorrect on PVC
+		 * at least. The following seems to work:
+		 *	r <<= 8;
+		 * However for now to be safe just use the default value
+		 * below. Once issue is resolved remove the one line below.
+		 */
+		r = FIELD_PREP(PKG_MAX_WIN, PKG_MAX_WIN_DEFAULT);
+	} else {
+		r = FIELD_PREP(PKG_MAX_WIN, PKG_MAX_WIN_DEFAULT);
+	}
+
+	/* Steps below are explained in i915_power1_max_interval_show() */
+	x = REG_FIELD_GET(PKG_MAX_WIN_X, r);
+	y = REG_FIELD_GET(PKG_MAX_WIN_Y, r);
+	tau4 = ((1 << x_w) | x) << y;
+	max_win = mul_u64_u32_shr(tau4, SF_TIME, hwmon->scl_shift_time + x_w);
+
+	if (val > max_win)
+		return -EINVAL;
+
+	/* val in hw units */
+	val = DIV_ROUND_CLOSEST_ULL((u64)val << hwmon->scl_shift_time, SF_TIME);
+	/* Convert to 1.x * power(2,y) */
+	if (!val)
+		return -EINVAL;
+	y = ilog2(val);
+	/* x = (val - (1 << y)) >> (y - 2); */
+	x = (val - (1ul << y)) << x_w >> y;
+
+	rxy = REG_FIELD_PREP(PKG_PWR_LIM_1_TIME_X, x) | REG_FIELD_PREP(PKG_PWR_LIM_1_TIME_Y, y);
+
+	hwm_locked_with_pm_intel_uncore_rmw(ddat, hwmon->rg.pkg_rapl_limit,
+					    PKG_PWR_LIM_1_TIME, rxy);
+	return count;
+}
+
+static SENSOR_DEVICE_ATTR(power1_max_interval, 0664,
+			  hwm_power1_max_interval_show,
+			  hwm_power1_max_interval_store, 0);
+
+static struct attribute *hwm_attributes[] = {
+	&sensor_dev_attr_power1_max_interval.dev_attr.attr,
+	NULL
+};
+
+static umode_t hwm_attributes_visible(struct kobject *kobj,
+				      struct attribute *attr, int index)
+{
+	struct device *dev = kobj_to_dev(kobj);
+	struct hwm_drvdata *ddat = dev_get_drvdata(dev);
+	struct i915_hwmon *hwmon = ddat->hwmon;
+
+	if (attr == &sensor_dev_attr_power1_max_interval.dev_attr.attr)
+		return i915_mmio_reg_valid(hwmon->rg.pkg_rapl_limit) ? attr->mode : 0;
+	else
+		return 0;
+}
+
+static const struct attribute_group hwm_attrgroup = {
+	.attrs = hwm_attributes,
+	.is_visible = hwm_attributes_visible,
+};
+
+static const struct attribute_group *hwm_groups[] = {
+	&hwm_attrgroup,
+	NULL
+};
+
 static const struct hwmon_channel_info *hwm_info[] = {
 	HWMON_CHANNEL_INFO(in, HWMON_I_INPUT),
 	HWMON_CHANNEL_INFO(power, HWMON_P_MAX | HWMON_P_RATED_MAX | HWMON_P_CRIT),
@@ -495,6 +620,7 @@  hwm_get_preregistration_info(struct drm_i915_private *i915)
 
 	hwmon->scl_shift_power = REG_FIELD_GET(PKG_PWR_UNIT, val_sku_unit);
 	hwmon->scl_shift_energy = REG_FIELD_GET(PKG_ENERGY_UNIT, val_sku_unit);
+	hwmon->scl_shift_time = REG_FIELD_GET(PKG_TIME_UNIT, val_sku_unit);
 
 	/*
 	 * Initialize 'struct hwm_energy_info', i.e. set fields to the
@@ -533,7 +659,7 @@  void i915_hwmon_register(struct drm_i915_private *i915)
 	hwmon_dev = hwmon_device_register_with_info(dev, ddat->name,
 						    ddat,
 						    &hwm_chip_info,
-						    NULL);
+						    hwm_groups);
 	if (IS_ERR(hwmon_dev)) {
 		mutex_destroy(&hwmon->hwmon_lock);
 		i915->hwmon = NULL;
diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index 041b858b95f4..05db98252a2f 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -1879,8 +1879,8 @@ 
 #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)
+#define     PKG_MAX_WIN_X		GENMASK_ULL(54, 53)
+#define     PKG_MAX_WIN_Y		GENMASK_ULL(52, 48)
 
 #define CHV_CLK_CTL1			_MMIO(0x101100)
 #define VLV_CLK_CTL2			_MMIO(0x101104)
diff --git a/drivers/gpu/drm/i915/intel_mchbar_regs.h b/drivers/gpu/drm/i915/intel_mchbar_regs.h
index 18fcfc39ca2f..930cb4d76bbb 100644
--- a/drivers/gpu/drm/i915/intel_mchbar_regs.h
+++ b/drivers/gpu/drm/i915/intel_mchbar_regs.h
@@ -204,6 +204,10 @@ 
 
 #define PCU_PACKAGE_RAPL_LIMIT			_MMIO(MCHBAR_MIRROR_BASE_SNB + 0x59a0)
 #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)
+#define   PKG_PWR_LIM_1_TIME_X			REG_GENMASK(23, 22)
+#define   PKG_PWR_LIM_1_TIME_Y			REG_GENMASK(21, 17)
 
 /* snb MCH registers for priority tuning */
 #define MCH_SSKPD				_MMIO(MCHBAR_MIRROR_BASE_SNB + 0x5d10)