drm/xe/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
PACKAGE_RAPL_LIMIT register (1.x * power(2,y))

v2: Get rpm wake ref while accessing power1_max_interval
v3: %s/hwmon/xe_hwmon/
v4:
- As power1_max_interval is rw attr take lock in read function as well
- Refine comment about val to fix point conversion (Andi)
- Update kernel version and date in doc
v5: Fix review comments (Anshuman)

Acked-by: Rodrigo Vivi <[e-mail]>
Reviewed-by: Himal Prasad Ghimiray <[e-mail]>
Reviewed-by: Anshuman Gupta <[e-mail]>
Signed-off-by: Badal Nilawar <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]
Signed-off-by: Rodrigo Vivi <[e-mail]>

Documentation/ABI/testing/sysfs-driver-intel-xe-hwmon

···
 Description:	RO. Energy input of device in microjoules.
 
 		Only supported for particular Intel xe graphics platforms.
+
+What:		/sys/devices/.../hwmon/hwmon<i>/power1_max_interval
+Date:		October 2023
+KernelVersion:	6.6
+Contact:	[e-mail]
+Description:	RW. Sustained power limit interval (Tau in PL1/Tau) in
+		milliseconds over which sustained power is averaged.
+
+		Only supported for particular Intel xe graphics platforms.

drivers/gpu/drm/xe/regs/xe_mchbar_regs.h

···
 #define   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_X			GENMASK_ULL(54, 53)
+#define     PKG_MAX_WIN_Y			GENMASK_ULL(52, 48)
+
 
 #define PCU_CR_PACKAGE_POWER_SKU_UNIT		XE_REG(MCHBAR_MIRROR_BASE_SNB + 0x5938)
 #define   PKG_PWR_UNIT				REG_GENMASK(3, 0)
 #define   PKG_ENERGY_UNIT			REG_GENMASK(12, 8)
+#define   PKG_TIME_UNIT				REG_GENMASK(19, 16)
 
 #define PCU_CR_PACKAGE_ENERGY_STATUS		XE_REG(MCHBAR_MIRROR_BASE_SNB + 0x593c)
 
 #define PCU_CR_PACKAGE_RAPL_LIMIT		XE_REG(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)
 
 #endif /* _XE_MCHBAR_REGS_H_ */

drivers/gpu/drm/xe/xe_hwmon.c

···
 #define SF_CURR		1000		/* milliamperes */
 #define SF_VOLTAGE	1000		/* millivolts */
 #define SF_ENERGY	1000000		/* microjoules */
+#define SF_TIME		1000		/* milliseconds */
 
 /**
  * struct xe_hwmon_energy_info - to accumulate energy
···
 	int scl_shift_power;
 	/** @scl_shift_energy: pkg energy unit */
 	int scl_shift_energy;
+	/** @scl_shift_time: pkg time unit */
+	int scl_shift_time;
 	/** @ei: Energy info for energy1_input */
 	struct xe_hwmon_energy_info ei;
 };
···
 	*energy = mul_u64_u32_shr(ei->accum_energy, SF_ENERGY,
 				  hwmon->scl_shift_energy);
 }
+
+static ssize_t
+xe_hwmon_power1_max_interval_show(struct device *dev, struct device_attribute *attr,
+				  char *buf)
+{
+	struct xe_hwmon *hwmon = dev_get_drvdata(dev);
+	u32 x, y, x_w = 2; /* 2 bits */
+	u64 r, tau4, out;
+
+	xe_device_mem_access_get(gt_to_xe(hwmon->gt));
+
+	mutex_lock(&hwmon->hwmon_lock);
+
+	xe_hwmon_process_reg(hwmon, REG_PKG_RAPL_LIMIT,
+			     REG_READ32, &r, 0, 0);
+
+	mutex_unlock(&hwmon->hwmon_lock);
+
+	xe_device_mem_access_put(gt_to_xe(hwmon->gt));
+
+	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)
+	 *
+	 * Here (y - 2) ensures a 1.x fixed point representation of 1.x
+	 * As x is 2 bits so 1.x can be 1.0, 1.25, 1.50, 1.75
+	 *
+	 * As y can be < 2, we compute tau4 = (4 | x) << y
+	 * and then 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
+xe_hwmon_power1_max_interval_store(struct device *dev, struct device_attribute *attr,
+				   const char *buf, size_t count)
+{
+	struct xe_hwmon *hwmon = dev_get_drvdata(dev);
+	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.
+	 *
+	 * The ideal scenario is for PKG_MAX_WIN to be read from the PKG_PWR_SKU register.
+	 * However, it is observed that existing discrete GPUs does not provide correct
+	 * PKG_MAX_WIN value, therefore a using default constant value. For future discrete GPUs
+	 * this may get resolved, in which case PKG_MAX_WIN should be obtained from PKG_PWR_SKU.
+	 */
+#define PKG_MAX_WIN_DEFAULT 0x12ull
+
+	/*
+	 * val must be < max in hwmon interface units. The steps below are
+	 * explained in xe_hwmon_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 val to 1.x * power(2,y)
+	 * y = ilog2(val)
+	 * x = (val - (1 << y)) >> (y - 2)
+	 */
+	if (!val) {
+		y = 0;
+		x = 0;
+	} else {
+		y = ilog2(val);
+		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);
+
+	xe_device_mem_access_get(gt_to_xe(hwmon->gt));
+
+	mutex_lock(&hwmon->hwmon_lock);
+
+	xe_hwmon_process_reg(hwmon, REG_PKG_RAPL_LIMIT, REG_RMW32, (u64 *)&r,
+			     PKG_PWR_LIM_1_TIME, rxy);
+
+	mutex_unlock(&hwmon->hwmon_lock);
+
+	xe_device_mem_access_put(gt_to_xe(hwmon->gt));
+
+	return count;
+}
+
+static SENSOR_DEVICE_ATTR(power1_max_interval, 0664,
+			  xe_hwmon_power1_max_interval_show,
+			  xe_hwmon_power1_max_interval_store, 0);
+
+static struct attribute *hwmon_attributes[] = {
+	&sensor_dev_attr_power1_max_interval.dev_attr.attr,
+	NULL
+};
+
+static umode_t xe_hwmon_attributes_visible(struct kobject *kobj,
+					   struct attribute *attr, int index)
+{
+	struct device *dev = kobj_to_dev(kobj);
+	struct xe_hwmon *hwmon = dev_get_drvdata(dev);
+	int ret = 0;
+
+	xe_device_mem_access_get(gt_to_xe(hwmon->gt));
+
+	if (attr == &sensor_dev_attr_power1_max_interval.dev_attr.attr)
+		ret = xe_hwmon_get_reg(hwmon, REG_PKG_RAPL_LIMIT) ? attr->mode : 0;
+
+	xe_device_mem_access_put(gt_to_xe(hwmon->gt));
+
+	return ret;
+}
+
+static const struct attribute_group hwmon_attrgroup = {
+	.attrs = hwmon_attributes,
+	.is_visible = xe_hwmon_attributes_visible,
+};
+
+static const struct attribute_group *hwmon_groups[] = {
+	&hwmon_attrgroup,
+	NULL
+};
 
 static const struct hwmon_channel_info *hwmon_info[] = {
 	HWMON_CHANNEL_INFO(power, HWMON_P_MAX | HWMON_P_RATED_MAX | HWMON_P_CRIT),
···
 				     REG_READ32, &val_sku_unit, 0, 0);
 		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);
 	}
 
 	/*
···
 	/*  hwmon_dev points to device hwmon<i> */
 	hwmon->hwmon_dev = devm_hwmon_device_register_with_info(dev, "xe", hwmon,
 								&hwmon_chip_info,
-								NULL);
+								hwmon_groups);
+
 	if (IS_ERR(hwmon->hwmon_dev)) {
 		drm_warn(&xe->drm, "Failed to register xe hwmon (%pe)\n", hwmon->hwmon_dev);
 		xe->hwmon = NULL;