Re: [PATCH v2] drm/i915/hwmon: expose fan speed

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Hi Raag

On 7/30/2024 11:35 AM, Raag Jadav wrote:
Add hwmon support for fan1_input attribute, which will expose fan speed
in RPM. With this in place we can monitor fan speed using lm-sensors tool.

$ sensors
i915-pci-0300
Adapter: PCI adapter
in0:         653.00 mV
fan1:        3833 RPM
power1:           N/A  (max =  43.00 W)
energy1:      32.02 kJ

v2:
- Add mutex protection
- Handle overflow
- Add ABI documentation
- Aesthetic adjustments

Signed-off-by: Raag Jadav <raag.jadav@xxxxxxxxx>
Add the name in front of the comments given by reviewer in version history

With that
Reviewed-by: Riana Tauro <riana.tauro@xxxxxxxxx>

---
  .../ABI/testing/sysfs-driver-intel-i915-hwmon |  8 ++
  drivers/gpu/drm/i915/gt/intel_gt_regs.h       |  2 +
  drivers/gpu/drm/i915/i915_hwmon.c             | 87 +++++++++++++++++++
  3 files changed, 97 insertions(+)

diff --git a/Documentation/ABI/testing/sysfs-driver-intel-i915-hwmon b/Documentation/ABI/testing/sysfs-driver-intel-i915-hwmon
index 92fe7c5c5ac1..b971f34b9bab 100644
--- a/Documentation/ABI/testing/sysfs-driver-intel-i915-hwmon
+++ b/Documentation/ABI/testing/sysfs-driver-intel-i915-hwmon
@@ -75,3 +75,11 @@ Description:	RO. Energy input of device or gt in microjoules.
  		for the gt.
Only supported for particular Intel i915 graphics platforms.
+
+What:		/sys/bus/pci/drivers/i915/.../hwmon/hwmon<i>/fan1_input
+Date:		August 2024
+KernelVersion:	6.11
+Contact:	intel-gfx@xxxxxxxxxxxxxxxxxxxxx
+Description:	RO. Fan speed of device in RPM.
+
+		Only supported for particular Intel i915 graphics platforms.
diff --git a/drivers/gpu/drm/i915/gt/intel_gt_regs.h b/drivers/gpu/drm/i915/gt/intel_gt_regs.h
index e42b3a5d4e63..57a3c83d3655 100644
--- a/drivers/gpu/drm/i915/gt/intel_gt_regs.h
+++ b/drivers/gpu/drm/i915/gt/intel_gt_regs.h
@@ -1553,6 +1553,8 @@
  #define VLV_RENDER_C0_COUNT			_MMIO(0x138118)
  #define VLV_MEDIA_C0_COUNT			_MMIO(0x13811c)
+#define PCU_PWM_FAN_SPEED _MMIO(0x138140)
+
  #define GEN12_RPSTAT1				_MMIO(0x1381b4)
  #define   GEN12_VOLTAGE_MASK			REG_GENMASK(10, 0)
  #define   GEN12_CAGF_MASK			REG_GENMASK(19, 11)
diff --git a/drivers/gpu/drm/i915/i915_hwmon.c b/drivers/gpu/drm/i915/i915_hwmon.c
index 49db3e09826c..e3c7c40ca88d 100644
--- a/drivers/gpu/drm/i915/i915_hwmon.c
+++ b/drivers/gpu/drm/i915/i915_hwmon.c
@@ -36,6 +36,7 @@ struct hwm_reg {
  	i915_reg_t pkg_rapl_limit;
  	i915_reg_t energy_status_all;
  	i915_reg_t energy_status_tile;
+	i915_reg_t fan_speed;
  };
struct hwm_energy_info {
@@ -43,11 +44,17 @@ struct hwm_energy_info {
  	long accum_energy;			/* Accumulated energy for energy1_input */
  };
+struct hwm_fan_info {
+	u32 reg_val_prev;
+	u32 time_prev;
+};
+
  struct hwm_drvdata {
  	struct i915_hwmon *hwmon;
  	struct intel_uncore *uncore;
  	struct device *hwmon_dev;
  	struct hwm_energy_info ei;		/*  Energy info for energy1_input */
+	struct hwm_fan_info fi;			/*  Fan info for fan1_input */
  	char name[12];
  	int gt_n;
  	bool reset_in_progress;
@@ -276,6 +283,7 @@ static const struct hwmon_channel_info * const hwm_info[] = {
  	HWMON_CHANNEL_INFO(power, HWMON_P_MAX | HWMON_P_RATED_MAX | HWMON_P_CRIT),
  	HWMON_CHANNEL_INFO(energy, HWMON_E_INPUT),
  	HWMON_CHANNEL_INFO(curr, HWMON_C_CRIT),
+	HWMON_CHANNEL_INFO(fan, HWMON_F_INPUT),
  	NULL
  };
@@ -613,6 +621,69 @@ hwm_curr_write(struct hwm_drvdata *ddat, u32 attr, long val)
  	}
  }
+static umode_t
+hwm_fan_is_visible(const struct hwm_drvdata *ddat, u32 attr)
+{
+	struct i915_hwmon *hwmon = ddat->hwmon;
+
+	switch (attr) {
+	case hwmon_fan_input:
+		return i915_mmio_reg_valid(hwmon->rg.fan_speed) ? 0444 : 0;
+	default:
+		return 0;
+	}
+}
+
+static int
+hwm_fan_read(struct hwm_drvdata *ddat, u32 attr, long *val)
+{
+	struct i915_hwmon *hwmon = ddat->hwmon;
+	struct hwm_fan_info *fi = &ddat->fi;
+	u32 reg_val, rotations, pulses, time, time_now;
+	intel_wakeref_t wakeref;
+	int ret = 0;
+
+	switch (attr) {
+	case hwmon_fan_input:
+		with_intel_runtime_pm(ddat->uncore->rpm, wakeref) {
+			mutex_lock(&hwmon->hwmon_lock);
+
+			reg_val = intel_uncore_read(ddat->uncore, hwmon->rg.fan_speed);
+			time_now = jiffies_to_msecs(jiffies);
+
+			/* Handle overflow */
+			if (reg_val >= fi->reg_val_prev)
+				pulses = reg_val - fi->reg_val_prev;
+			else
+				pulses = UINT_MAX - fi->reg_val_prev + reg_val;
+
+			/*
+			 * HW register value is accumulated count of pulses from
+			 * PWM fan with the scale of 2 pulses per rotation.
+			 */
+			rotations = pulses >> 1;
+			time = time_now - fi->time_prev;
+
+			if (unlikely(!time)) {
+				ret = -EAGAIN;
+				mutex_unlock(&hwmon->hwmon_lock);
+				break;
+			}
+
+			/* Convert to minutes for calculating RPM */
+			*val = DIV_ROUND_UP((long)rotations * (60 * MSEC_PER_SEC), time);
+
+			fi->reg_val_prev = reg_val;
+			fi->time_prev = time_now;
+
+			mutex_unlock(&hwmon->hwmon_lock);
+		}
+		return ret;
+	default:
+		return -EOPNOTSUPP;
+	}
+}
+
  static umode_t
  hwm_is_visible(const void *drvdata, enum hwmon_sensor_types type,
  	       u32 attr, int channel)
@@ -628,6 +699,8 @@ hwm_is_visible(const void *drvdata, enum hwmon_sensor_types type,
  		return hwm_energy_is_visible(ddat, attr);
  	case hwmon_curr:
  		return hwm_curr_is_visible(ddat, attr);
+	case hwmon_fan:
+		return hwm_fan_is_visible(ddat, attr);
  	default:
  		return 0;
  	}
@@ -648,6 +721,8 @@ hwm_read(struct device *dev, enum hwmon_sensor_types type, u32 attr,
  		return hwm_energy_read(ddat, attr, val);
  	case hwmon_curr:
  		return hwm_curr_read(ddat, attr, val);
+	case hwmon_fan:
+		return hwm_fan_read(ddat, attr, val);
  	default:
  		return -EOPNOTSUPP;
  	}
@@ -739,12 +814,14 @@ hwm_get_preregistration_info(struct drm_i915_private *i915)
  		hwmon->rg.pkg_rapl_limit = PCU_PACKAGE_RAPL_LIMIT;
  		hwmon->rg.energy_status_all = PCU_PACKAGE_ENERGY_STATUS;
  		hwmon->rg.energy_status_tile = INVALID_MMIO_REG;
+		hwmon->rg.fan_speed = PCU_PWM_FAN_SPEED;
  	} else {
  		hwmon->rg.pkg_power_sku_unit = INVALID_MMIO_REG;
  		hwmon->rg.pkg_power_sku = INVALID_MMIO_REG;
  		hwmon->rg.pkg_rapl_limit = INVALID_MMIO_REG;
  		hwmon->rg.energy_status_all = INVALID_MMIO_REG;
  		hwmon->rg.energy_status_tile = INVALID_MMIO_REG;
+		hwmon->rg.fan_speed = INVALID_MMIO_REG;
  	}
with_intel_runtime_pm(uncore->rpm, wakeref) {
@@ -755,6 +832,16 @@ hwm_get_preregistration_info(struct drm_i915_private *i915)
  		if (i915_mmio_reg_valid(hwmon->rg.pkg_power_sku_unit))
  			val_sku_unit = intel_uncore_read(uncore,
  							 hwmon->rg.pkg_power_sku_unit);
+
+		/*
+		 * Store the initial fan register value, so that we can use it for
+		 * initial fan speed calculation.
+		 */
+		if (i915_mmio_reg_valid(hwmon->rg.fan_speed)) {
+			ddat->fi.reg_val_prev = intel_uncore_read(uncore,
+								  hwmon->rg.fan_speed);
+			ddat->fi.time_prev = jiffies_to_msecs(jiffies);
+		}
  	}
hwmon->scl_shift_power = REG_FIELD_GET(PKG_PWR_UNIT, val_sku_unit);



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