leds: bcm63138: Handle shift register config

This adds code to optionally read the width of the shift register
chain from the device tree and use it to set up the register
controlling the shifter hardware.

If the property is not present, the boot-time default is used so
existing device trees keep working as this is what they assume.

Signed-off-by: Linus Walleij <[email protected]>
Reviewed-by: Florian Fainelli <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Lee Jones <[email protected]>

Author: Linus Walleij

drivers/leds/blink/leds-bcm63138.c

@@ -2,6 +2,7 @@
 /*
  * Copyright (C) 2021 Rafał Miłecki <[email protected]>
  */
+#include <linux/bits.h>
 #include <linux/cleanup.h>
 #include <linux/delay.h>
 #include <linux/io.h>
@@ -254,6 +255,7 @@ static int bcm63138_leds_probe(struct platform_device *pdev)
 	struct device_node *np = dev_of_node(&pdev->dev);
 	struct device *dev = &pdev->dev;
 	struct bcm63138_leds *leds;
+	u32 shift_bits;
 
 	leds = devm_kzalloc(dev, sizeof(*leds), GFP_KERNEL);
 	if (!leds)
@@ -267,6 +269,12 @@ static int bcm63138_leds_probe(struct platform_device *pdev)
 
 	spin_lock_init(&leds->lock);
 
+	/* If this property is not present, we use boot defaults */
+	if (!of_property_read_u32(np, "brcm,serial-shift-bits", &shift_bits)) {
+		bcm63138_leds_write(leds, BCM63138_SERIAL_LED_SHIFT_SEL,
+				    GENMASK(shift_bits - 1, 0));
+	}
+
 	bcm63138_leds_write(leds, BCM63138_GLB_CTRL,
 			    BCM63138_GLB_CTRL_SERIAL_LED_DATA_PPOL |
 			    BCM63138_GLB_CTRL_SERIAL_LED_EN_POL);