[PATCH v3 11/19] hwmon: (mr75203) add VM pre-scaler support

[Eliav Farber <farbere@amazon.com>]

Add mr76006 pre-scaler support to normalize the voltage output result for
channels that use pre-scaler units to get the measurement to be within
the range that the sensor supports.

For channels that are listed in the device-tree to have a pre-scaler, the
voltage result is multiplied by a factor of 2, to represent to the user
the actual voltage source which is measured.

Signed-off-by: Eliav Farber <farbere@amazon.com>
---
V3 -> V2:
- Modify code according to new property format.

 drivers/hwmon/mr75203.c | 64 +++++++++++++++++++++++++++++++++++++++--
 1 file changed, 62 insertions(+), 2 deletions(-)

diff --git a/drivers/hwmon/mr75203.c b/drivers/hwmon/mr75203.c
index 6925e8490587..1cd5ff6eacce 100644
--- a/drivers/hwmon/mr75203.c
+++ b/drivers/hwmon/mr75203.c
@@ -13,10 +13,12 @@
 #include <linux/module.h>
 #include <linux/mod_devicetable.h>
 #include <linux/mutex.h>
+#include <linux/of.h>
 #include <linux/platform_device.h>
 #include <linux/property.h>
 #include <linux/regmap.h>
 #include <linux/reset.h>
+#include <linux/slab.h>
 
 /* PVT Common register */
 #define PVT_IP_CONFIG	0x04
@@ -108,9 +110,13 @@
 #define PVT_N_CONST		90
 #define PVT_R_CONST		245805
 
+#define PRE_SCALER_X1	1
+#define PRE_SCALER_X2	2
+
 struct voltage_device {
 	u32 vm_map;	/* Map channel number to VM index */
 	u32 ch_map;	/* Map channel number to channel index */
+	u32 pre_scaler;
 };
 
 struct voltage_channels {
@@ -192,7 +198,7 @@ static int pvt_read_in(struct device *dev, u32 attr, int channel, long *val)
 {
 	struct pvt_device *pvt = dev_get_drvdata(dev);
 	struct regmap *v_map = pvt->v_map;
-	u32 n, stat;
+	u32 n, stat, pre_scaler;
 	u8 vm_idx, ch_idx;
 	int ret;
 
@@ -217,7 +223,9 @@ static int pvt_read_in(struct device *dev, u32 attr, int channel, long *val)
 
 		n &= SAMPLE_DATA_MSK;
 		/* Convert the N bitstream count into voltage */
-		*val = (PVT_N_CONST * n - PVT_R_CONST) >> PVT_CONV_BITS;
+		pre_scaler = pvt->vd[channel].pre_scaler;
+		*val = pre_scaler * (PVT_N_CONST * n - PVT_R_CONST) >>
+			PVT_CONV_BITS;
 
 		return 0;
 	default:
@@ -582,6 +590,54 @@ static int pvt_get_active_channel(struct device *dev, struct pvt_device *pvt,
 	return 0;
 }
 
+static int pvt_get_pre_scaler(struct device *dev, struct pvt_device *pvt)
+{
+	const struct device_node *np = dev->of_node;
+	u32 total_channels = pvt->vm_channels.total;
+	u32 channel;
+	u8 *pre_scaler_ch_list;
+	int i, ret, num_ch;
+
+	/* Set default pre-scaler value to be 1. */
+	for (i = 0; i < total_channels; i++)
+		pvt->vd[i].pre_scaler = PRE_SCALER_X1;
+
+	/* Get number of channels configured in "moortec,vm-pre-scaler". */
+	num_ch = of_property_count_u8_elems(np, "moortec,vm-pre-scaler");
+	if (num_ch <= 0)
+		return 0;
+
+	pre_scaler_ch_list = kcalloc(total_channels,
+				     sizeof(*pre_scaler_ch_list), GFP_KERNEL);
+	if (!pre_scaler_ch_list)
+		return -ENOMEM;
+
+	/* Get list of all channels that have pre-scaler of 2. */
+	ret = device_property_read_u8_array(dev, "moortec,vm-pre-scaler",
+					    pre_scaler_ch_list, num_ch);
+	if (ret)
+		goto out;
+
+	for (i = 0; i < num_ch; i++) {
+		channel = pre_scaler_ch_list[i];
+
+		if (channel >= total_channels) {
+			dev_err(dev,
+				"invalid channel (%u) in pre-scaler list\n",
+				channel);
+			ret = -EINVAL;
+			goto out;
+		}
+
+		pvt->vd[channel].pre_scaler = PRE_SCALER_X2;
+	}
+
+out:
+	kfree(pre_scaler_ch_list);
+
+	return ret;
+}
+
 static int mr75203_probe(struct platform_device *pdev)
 {
 	const struct hwmon_channel_info **pvt_info;
@@ -697,6 +753,10 @@ static int mr75203_probe(struct platform_device *pdev)
 		if (ret)
 			return ret;
 
+		ret = pvt_get_pre_scaler(dev, pvt);
+		if (ret)
+			return ret;
+
 		in_config = devm_kcalloc(dev, pvt->vm_channels.total + 1,
 					 sizeof(*in_config), GFP_KERNEL);
 		if (!in_config)
-- 
2.37.1