drm/i915/hwmon: Expose power1_max_interval

Expose power1_max_interval, that is the tau corresponding to PL1, as a
custom hwmon attribute. 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)
v3: Cleaned up hwm_power1_max_interval_store() (Badal)
v4:
  - Fixed review comments (Anshuman)
  - In hwm_power1_max_interval_store() get PKG_MAX_WIN from
    pkg_power_sku when it is valid (Ashutosh)
  - KernelVersion: 6.2, Date: February 2023 in doc (Tvrtko)
v5: On some of the DGFX setups it is seen that although pkg_power_sku
    is valid the field PKG_WIN_MAX is not populated. So it is
    decided to stick to default value of PKG_WIN_MAX (Ashutosh)
v6: Change contact to intel-gfx (Rodrigo)
    Fixed variable types in hwm_power1_max_interval_store (Andi)
    Documented PKG_MAX_WIN_DEFAULT (Andi)
    Removed else in hwm_attributes_visible (Andi)

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>
Reviewed-by: Anshuman Gupta <anshuman.gupta@intel.com>
Signed-off-by: Anshuman Gupta <anshuman.gupta@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221013154526.2105579-7-ashutosh.dixit@intel.com

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:		February 2023
+KernelVersion:	6.2
+Contact:	intel-gfx@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:		February 2023
 KernelVersion:	6.2

drivers/gpu/drm/i915/i915_hwmon.c

@@ -20,11 +20,13 @@
  * - power  - microwatts
  * - curr   - milliamperes
  * - energy - microjoules
+ * - time   - milliseconds
  */
 #define SF_VOLTAGE	1000
 #define SF_POWER	1000000
 #define SF_CURR		1000
 #define SF_ENERGY	1000000
+#define SF_TIME		1000
 
 struct hwm_reg {
 	i915_reg_t gt_perf_status;
@@ -53,6 +55,7 @@ struct i915_hwmon {
 	struct hwm_reg rg;
 	int scl_shift_power;
 	int scl_shift_energy;
+	int scl_shift_time;
 };
 
 static void
@@ -159,6 +162,119 @@ hwm_energy(struct hwm_drvdata *ddat, long *energy)
 	mutex_unlock(&hwmon->hwmon_lock);
 }
 
+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;
+	u32 x, y, rxy, x_w = 2; /* 2 bits */
+	u64 tau4, r, max_win;
+	unsigned long val;
+	int ret;
+
+	ret = kstrtoul(buf, 0, &val);
+	if (ret)
+		return ret;
+
+	/*
+	 * Max HW supported tau in '1.x * power(2,y)' format, x = 0, y = 0x12
+	 * The hwmon->scl_shift_time default of 0xa results in a max tau of 256 seconds
+	 */
+#define PKG_MAX_WIN_DEFAULT 0x12ull
+
+	/*
+	 * val must be < max in hwmon interface units. The steps below are
+	 * explained in i915_power1_max_interval_show()
+	 */
+	r = FIELD_PREP(PKG_MAX_WIN, PKG_MAX_WIN_DEFAULT);
+	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;
+
+	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),
@@ -471,6 +587,7 @@ 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
@@ -509,7 +626,7 @@ void i915_hwmon_register(struct drm_i915_private *i915)
 	hwmon_dev = devm_hwmon_device_register_with_info(dev, ddat->name,
 							 ddat,
 							 &hwm_chip_info,
-							 NULL);
+							 hwm_groups);
 	if (IS_ERR(hwmon_dev)) {
 		i915->hwmon = NULL;
 		return;

drivers/gpu/drm/i915/intel_mchbar_regs.h

@@ -194,6 +194,9 @@
  */
 #define PCU_PACKAGE_POWER_SKU			_MMIO(MCHBAR_MIRROR_BASE_SNB + 0x5930)
 #define   PKG_PKG_TDP				GENMASK_ULL(14, 0)
+#define   PKG_MAX_WIN				GENMASK_ULL(54, 48)
+#define     PKG_MAX_WIN_X			GENMASK_ULL(54, 53)
+#define     PKG_MAX_WIN_Y			GENMASK_ULL(52, 48)
 
 #define PCU_PACKAGE_POWER_SKU_UNIT		_MMIO(MCHBAR_MIRROR_BASE_SNB + 0x5938)
 #define   PKG_PWR_UNIT				REG_GENMASK(3, 0)
@@ -212,6 +215,10 @@
 #define   RPE_MASK				REG_GENMASK(15, 8)
 #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)