linux-kernel - [PATCH v2 2/3] hwmon: (tps23861) reduce count of i2c transactions for port

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Date:   Tue,  6 Sep 2022 20:54:04 -0500
From:   Alexandru Gagniuc <mr.nuke.me@...il.com>
To:     linux@...ck-us.net, linux-hwmon@...r.kernel.org
Cc:     robert.marko@...tura.hr, luka.perkov@...tura.hr, jdelvare@...e.com,
        dev@...ehler.at, linux-kernel@...r.kernel.org,
        Alexandru Gagniuc <mr.nuke.me@...il.com>
Subject: [PATCH v2 2/3] hwmon: (tps23861) reduce count of i2c transactions for port_status

When reading the 'port_status' debugfs entry, some I2C registers were
read more than once. This looks inefficient in an I2C trace.

To reduce I2C traffic, update tps23861_port_status_show() to only read
each register once. Indexing the port number from 0 instead of 1 also
allows simplifying things a bit.

Signed-off-by: Alexandru Gagniuc <mr.nuke.me@...il.com>
---
Changes since v1:
  - Do not brag about negative line count in commit message
  - Do not change port number in port_status output

 drivers/hwmon/tps23861.c | 79 ++++++++++++----------------------------
 1 file changed, 24 insertions(+), 55 deletions(-)

diff --git a/drivers/hwmon/tps23861.c b/drivers/hwmon/tps23861.c
index f7c59ff7ae8e..019009b71a90 100644
--- a/drivers/hwmon/tps23861.c
+++ b/drivers/hwmon/tps23861.c
@@ -372,29 +372,12 @@ static const struct hwmon_chip_info tps23861_chip_info = {
 	.info = tps23861_info,
 };
 
-static char *tps23861_port_operating_mode(struct tps23861_data *data, int port)
+static char *port_operating_mode_string(uint8_t mode_reg, unsigned int port)
 {
-	unsigned int regval;
-	int mode;
+	unsigned int mode = ~0;
 
-	regmap_read(data->regmap, OPERATING_MODE, &regval);
-
-	switch (port) {
-	case 1:
-		mode = FIELD_GET(OPERATING_MODE_PORT_1_MASK, regval);
-		break;
-	case 2:
-		mode = FIELD_GET(OPERATING_MODE_PORT_2_MASK, regval);
-		break;
-	case 3:
-		mode = FIELD_GET(OPERATING_MODE_PORT_3_MASK, regval);
-		break;
-	case 4:
-		mode = FIELD_GET(OPERATING_MODE_PORT_4_MASK, regval);
-		break;
-	default:
-		mode = -EINVAL;
-	}
+	if (port < TPS23861_NUM_PORTS)
+		mode = (mode_reg >> (2 * port)) & OPERATING_MODE_PORT_1_MASK;
 
 	switch (mode) {
 	case OPERATING_MODE_OFF:
@@ -410,15 +393,9 @@ static char *tps23861_port_operating_mode(struct tps23861_data *data, int port)
 	}
 }
 
-static char *tps23861_port_detect_status(struct tps23861_data *data, int port)
+static char *port_detect_status_string(uint8_t status_reg)
 {
-	unsigned int regval;
-
-	regmap_read(data->regmap,
-		    PORT_1_STATUS + (port - 1),
-		    &regval);
-
-	switch (FIELD_GET(PORT_STATUS_DETECT_MASK, regval)) {
+	switch (FIELD_GET(PORT_STATUS_DETECT_MASK, status_reg)) {
 	case PORT_DETECT_UNKNOWN:
 		return "Unknown device";
 	case PORT_DETECT_SHORT:
@@ -448,15 +425,9 @@ static char *tps23861_port_detect_status(struct tps23861_data *data, int port)
 	}
 }
 
-static char *tps23861_port_class_status(struct tps23861_data *data, int port)
+static char *port_class_status_string(uint8_t status_reg)
 {
-	unsigned int regval;
-
-	regmap_read(data->regmap,
-		    PORT_1_STATUS + (port - 1),
-		    &regval);
-
-	switch (FIELD_GET(PORT_STATUS_CLASS_MASK, regval)) {
+	switch (FIELD_GET(PORT_STATUS_CLASS_MASK, status_reg)) {
 	case PORT_CLASS_UNKNOWN:
 		return "Unknown";
 	case PORT_CLASS_RESERVED:
@@ -479,16 +450,9 @@ static char *tps23861_port_class_status(struct tps23861_data *data, int port)
 	}
 }
 
-static char *tps23861_port_poe_plus_status(struct tps23861_data *data, int port)
+static char *port_poe_plus_status_string(uint8_t poe_plus, unsigned int port)
 {
-	unsigned int regval;
-
-	regmap_read(data->regmap, POE_PLUS, &regval);
-
-	if (BIT(port + 3) & regval)
-		return "Yes";
-	else
-		return "No";
+	return (BIT(port + 4) & poe_plus) ? "Yes" : "No";
 }
 
 static int tps23861_port_resistance(struct tps23861_data *data, int port)
@@ -497,7 +461,7 @@ static int tps23861_port_resistance(struct tps23861_data *data, int port)
 	__le16 regval;
 
 	regmap_bulk_read(data->regmap,
-			 PORT_1_RESISTANCE_LSB + PORT_N_RESISTANCE_LSB_OFFSET * (port - 1),
+			 PORT_1_RESISTANCE_LSB + PORT_N_RESISTANCE_LSB_OFFSET * port,
 			 &regval,
 			 2);
 
@@ -517,14 +481,19 @@ static int tps23861_port_resistance(struct tps23861_data *data, int port)
 static int tps23861_port_status_show(struct seq_file *s, void *data)
 {
 	struct tps23861_data *priv = s->private;
-	int i;
-
-	for (i = 1; i < TPS23861_NUM_PORTS + 1; i++) {
-		seq_printf(s, "Port: \t\t%d\n", i);
-		seq_printf(s, "Operating mode: %s\n", tps23861_port_operating_mode(priv, i));
-		seq_printf(s, "Detected: \t%s\n", tps23861_port_detect_status(priv, i));
-		seq_printf(s, "Class: \t\t%s\n", tps23861_port_class_status(priv, i));
-		seq_printf(s, "PoE Plus: \t%s\n", tps23861_port_poe_plus_status(priv, i));
+	unsigned int i, mode, poe_plus, status;
+
+	regmap_read(priv->regmap, OPERATING_MODE, &mode);
+	regmap_read(priv->regmap, POE_PLUS, &poe_plus);
+
+	for (i = 0; i < TPS23861_NUM_PORTS; i++) {
+		regmap_read(priv->regmap, PORT_1_STATUS + i, &status);
+
+		seq_printf(s, "Port: \t\t%d\n", i + 1);
+		seq_printf(s, "Operating mode: %s\n", port_operating_mode_string(mode, i));
+		seq_printf(s, "Detected: \t%s\n", port_detect_status_string(status));
+		seq_printf(s, "Class: \t\t%s\n", port_class_status_string(status));
+		seq_printf(s, "PoE Plus: \t%s\n", port_poe_plus_status_string(poe_plus, i));
 		seq_printf(s, "Resistance: \t%d\n", tps23861_port_resistance(priv, i));
 		seq_putc(s, '\n');
 	}
-- 
2.34.3