drm/xe/hwmon: Expose input voltage attribute

Use Xe HWMON subsystem to display the input voltage.

v2:
  - Rename hwm_get_vltg to hwm_get_voltage (Riana)
  - Use scale factor SF_VOLTAGE (Riana)
v3:
  - %s/gt_perf_status/REG_GT_PERF_STATUS/
  - Remove platform check from hwmon_get_voltage()
v4:
  - Fix review comments (Andi)

Acked-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Riana Tauro <riana.tauro@intel.com>
Signed-off-by: Badal Nilawar <badal.nilawar@intel.com>
Reviewed-by: Andi Shyti <andi.shyti@linux.intel.com>
Link: https://lore.kernel.org/r/20230925081842.3566834-4-badal.nilawar@intel.com
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

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

@@ -44,5 +44,11 @@ Description:	RW. Card reactive critical (I1) power limit in milliamperes.
 		the operating frequency if the power averaged over a window
 		exceeds this limit.
 
+What:		/sys/devices/.../hwmon/hwmon<i>/in0_input
+Date:		September 2023
+KernelVersion:	6.5
+Contact:	intel-xe@lists.freedesktop.org
+Description:	RO. Current Voltage in millivolt.
+
 		Only supported for particular Intel xe graphics platforms.
 

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

@@ -375,6 +375,9 @@
 #define GT_GFX_RC6_LOCKED			XE_REG(0x138104)
 #define GT_GFX_RC6				XE_REG(0x138108)
 
+#define GT_PERF_STATUS				XE_REG(0x1381b4)
+#define   VOLTAGE_MASK				REG_GENMASK(10, 0)
+
 #define GT_INTR_DW(x)				XE_REG(0x190018 + ((x) * 4))
 
 #define GUC_SG_INTR_ENABLE			XE_REG(0x190038)

drivers/gpu/drm/xe/xe_hwmon.c

@@ -3,7 +3,9 @@
  * Copyright © 2023 Intel Corporation
  */
 
+#include <linux/hwmon-sysfs.h>
 #include <linux/hwmon.h>
+#include <linux/types.h>
 
 #include <drm/drm_managed.h>
 #include "regs/xe_gt_regs.h"
@@ -19,6 +21,7 @@ enum xe_hwmon_reg {
 	REG_PKG_RAPL_LIMIT,
 	REG_PKG_POWER_SKU,
 	REG_PKG_POWER_SKU_UNIT,
+	REG_GT_PERF_STATUS,
 };
 
 enum xe_hwmon_reg_operation {
@@ -32,6 +35,7 @@ enum xe_hwmon_reg_operation {
  */
 #define SF_POWER	1000000		/* microwatts */
 #define SF_CURR		1000		/* milliamperes */
+#define SF_VOLTAGE	1000		/* millivolts */
 
 struct xe_hwmon {
 	struct device *hwmon_dev;
@@ -64,6 +68,10 @@ static u32 xe_hwmon_get_reg(struct xe_hwmon *hwmon, enum xe_hwmon_reg hwmon_reg)
 		else if (xe->info.platform == XE_PVC)
 			reg = PVC_GT0_PACKAGE_POWER_SKU_UNIT;
 		break;
+	case REG_GT_PERF_STATUS:
+		if (xe->info.platform == XE_DG2)
+			reg = GT_PERF_STATUS;
+		break;
 	default:
 		drm_warn(&xe->drm, "Unknown xe hwmon reg id: %d\n", hwmon_reg);
 		break;
@@ -189,6 +197,7 @@ static int xe_hwmon_power_rated_max_read(struct xe_hwmon *hwmon, long *value)
 static const struct hwmon_channel_info *hwmon_info[] = {
 	HWMON_CHANNEL_INFO(power, HWMON_P_MAX | HWMON_P_RATED_MAX | HWMON_P_CRIT),
 	HWMON_CHANNEL_INFO(curr, HWMON_C_CRIT),
+	HWMON_CHANNEL_INFO(in, HWMON_I_INPUT),
 	NULL
 };
 
@@ -211,6 +220,18 @@ static int xe_hwmon_pcode_write_i1(struct xe_gt *gt, u32 uval)
 			      uval);
 }
 
+static int xe_hwmon_get_voltage(struct xe_hwmon *hwmon, long *value)
+{
+	u32 reg_val;
+
+	xe_hwmon_process_reg(hwmon, REG_GT_PERF_STATUS,
+			     REG_READ, &reg_val, 0, 0);
+	/* HW register value in units of 2.5 millivolt */
+	*value = DIV_ROUND_CLOSEST(REG_FIELD_GET(VOLTAGE_MASK, reg_val) * 2500, SF_VOLTAGE);
+
+	return 0;
+}
+
 static umode_t
 xe_hwmon_power_is_visible(struct xe_hwmon *hwmon, u32 attr, int chan)
 {
@@ -319,6 +340,37 @@ xe_hwmon_curr_write(struct xe_hwmon *hwmon, u32 attr, long val)
 	}
 }
 
+static umode_t
+xe_hwmon_in_is_visible(struct xe_hwmon *hwmon, u32 attr)
+{
+	switch (attr) {
+	case hwmon_in_input:
+		return xe_hwmon_get_reg(hwmon, REG_GT_PERF_STATUS) ? 0444 : 0;
+	default:
+		return 0;
+	}
+}
+
+static int
+xe_hwmon_in_read(struct xe_hwmon *hwmon, u32 attr, long *val)
+{
+	int ret;
+
+	xe_device_mem_access_get(gt_to_xe(hwmon->gt));
+
+	switch (attr) {
+	case hwmon_in_input:
+		ret = xe_hwmon_get_voltage(hwmon, val);
+		break;
+	default:
+		ret = -EOPNOTSUPP;
+	}
+
+	xe_device_mem_access_put(gt_to_xe(hwmon->gt));
+
+	return ret;
+}
+
 static umode_t
 xe_hwmon_is_visible(const void *drvdata, enum hwmon_sensor_types type,
 		    u32 attr, int channel)
@@ -335,6 +387,9 @@ xe_hwmon_is_visible(const void *drvdata, enum hwmon_sensor_types type,
 	case hwmon_curr:
 		ret = xe_hwmon_curr_is_visible(hwmon, attr);
 		break;
+	case hwmon_in:
+		ret = xe_hwmon_in_is_visible(hwmon, attr);
+		break;
 	default:
 		ret = 0;
 		break;
@@ -361,6 +416,9 @@ xe_hwmon_read(struct device *dev, enum hwmon_sensor_types type, u32 attr,
 	case hwmon_curr:
 		ret = xe_hwmon_curr_read(hwmon, attr, val);
 		break;
+	case hwmon_in:
+		ret = xe_hwmon_in_read(hwmon, attr, val);
+		break;
 	default:
 		ret = -EOPNOTSUPP;
 		break;