leds: pca955x: Optimize probe LED selection

Previously, the probe function might do up to 32 reads and writes
to the same 4 registers to program the LED selection. Reduce this to
a maximum of 5 operations by accumulating the changes to the LED
selection and comparing with the previous value to write the
selection if different.

Signed-off-by: Eddie James <eajames@linux.ibm.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Link: https://lore.kernel.org/r/20250212143038.1416501-4-eajames@linux.ibm.com
Signed-off-by: Lee Jones <lee@kernel.org>

Author: Eddie James

drivers/leds/leds-pca955x.c

@@ -446,7 +446,9 @@ static int pca955x_probe(struct i2c_client *client)
 	struct led_classdev *led;
 	struct led_init_data init_data;
 	struct i2c_adapter *adapter;
-	int i, err;
+	int i, bit, err, nls, reg;
+	u8 ls1[4];
+	u8 ls2[4];
 	struct pca955x_platform_data *pdata;
 	bool set_default_label = false;
 	bool keep_pwm = false;
@@ -504,6 +506,17 @@ static int pca955x_probe(struct i2c_client *client)
 	init_data.devname_mandatory = false;
 	init_data.devicename = "pca955x";
 
+	nls = pca955x_num_led_regs(chip->bits);
+	/* Use auto-increment feature to read all the LED selectors at once. */
+	err = i2c_smbus_read_i2c_block_data(client,
+					    0x10 | (pca955x_num_input_regs(chip->bits) + 4), nls,
+					    ls1);
+	if (err < 0)
+		return err;
+
+	for (i = 0; i < nls; i++)
+		ls2[i] = ls1[i];
+
 	for (i = 0; i < chip->bits; i++) {
 		pca955x_led = &pca955x->leds[i];
 		pca955x_led->led_num = i;
@@ -515,19 +528,16 @@ static int pca955x_probe(struct i2c_client *client)
 		case PCA955X_TYPE_GPIO:
 			break;
 		case PCA955X_TYPE_LED:
+			bit = i % 4;
+			reg = i / 4;
 			led = &pca955x_led->led_cdev;
 			led->brightness_set_blocking = pca955x_led_set;
 			led->brightness_get = pca955x_led_get;
 
-			if (pdata->leds[i].default_state == LEDS_DEFSTATE_OFF) {
-				err = pca955x_led_set(led, LED_OFF);
-				if (err)
-					return err;
-			} else if (pdata->leds[i].default_state == LEDS_DEFSTATE_ON) {
-				err = pca955x_led_set(led, LED_FULL);
-				if (err)
-					return err;
-			}
+			if (pdata->leds[i].default_state == LEDS_DEFSTATE_OFF)
+				ls2[reg] = pca955x_ledsel(ls2[reg], bit, PCA955X_LS_LED_OFF);
+			else if (pdata->leds[i].default_state == LEDS_DEFSTATE_ON)
+				ls2[reg] = pca955x_ledsel(ls2[reg], bit, PCA955X_LS_LED_ON);
 
 			init_data.fwnode = pdata->leds[i].fwnode;
 
@@ -571,6 +581,14 @@ static int pca955x_probe(struct i2c_client *client)
 		}
 	}
 
+	for (i = 0; i < nls; i++) {
+		if (ls1[i] != ls2[i]) {
+			err = pca955x_write_ls(pca955x, i, ls2[i]);
+			if (err)
+				return err;
+		}
+	}
+
 	/* PWM0 is used for half brightness or 50% duty cycle */
 	err = pca955x_write_pwm(pca955x, 0, 255 - LED_HALF);
 	if (err)