phy: tusb1210: use bitmasks to set VENDOR_SPECIFIC2

Start by reading the content of the VENDOR_SPECIFIC2 register and update
each bit field based on device properties when defined.

The use of bit masks prevents fields from overriding each other and
enables users to clear bits which are set by default, like datapolarity
in this instance.

Signed-off-by: Liam Beguin <lvb@xiphos.com>
Link: https://lore.kernel.org/r/20201211191241.21306-1-liambeguin@gmail.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>

drivers/phy/ti/phy-tusb1210.c

@@ -7,15 +7,16 @@
  * Author: Heikki Krogerus <heikki.krogerus@linux.intel.com>
  */
 #include <linux/module.h>
+#include <linux/bitfield.h>
 #include <linux/ulpi/driver.h>
 #include <linux/ulpi/regs.h>
 #include <linux/gpio/consumer.h>
 #include <linux/phy/ulpi_phy.h>
 
 #define TUSB1210_VENDOR_SPECIFIC2		0x80
-#define TUSB1210_VENDOR_SPECIFIC2_IHSTX_SHIFT	0
-#define TUSB1210_VENDOR_SPECIFIC2_ZHSDRV_SHIFT	4
-#define TUSB1210_VENDOR_SPECIFIC2_DP_SHIFT	6
+#define TUSB1210_VENDOR_SPECIFIC2_IHSTX_MASK	GENMASK(3, 0)
+#define TUSB1210_VENDOR_SPECIFIC2_ZHSDRV_MASK	GENMASK(5, 4)
+#define TUSB1210_VENDOR_SPECIFIC2_DP_MASK	BIT(6)
 
 struct tusb1210 {
 	struct ulpi *ulpi;
@@ -118,22 +119,22 @@ static int tusb1210_probe(struct ulpi *ulpi)
 	 * diagram optimization and DP/DM swap.
 	 */
 
+	reg = ulpi_read(ulpi, TUSB1210_VENDOR_SPECIFIC2);
+
 	/* High speed output drive strength configuration */
-	device_property_read_u8(&ulpi->dev, "ihstx", &val);
-	reg = val << TUSB1210_VENDOR_SPECIFIC2_IHSTX_SHIFT;
+	if (!device_property_read_u8(&ulpi->dev, "ihstx", &val))
+		u8p_replace_bits(&reg, val, (u8)TUSB1210_VENDOR_SPECIFIC2_IHSTX_MASK);
 
 	/* High speed output impedance configuration */
-	device_property_read_u8(&ulpi->dev, "zhsdrv", &val);
-	reg |= val << TUSB1210_VENDOR_SPECIFIC2_ZHSDRV_SHIFT;
+	if (!device_property_read_u8(&ulpi->dev, "zhsdrv", &val))
+		u8p_replace_bits(&reg, val, (u8)TUSB1210_VENDOR_SPECIFIC2_ZHSDRV_MASK);
 
 	/* DP/DM swap control */
-	device_property_read_u8(&ulpi->dev, "datapolarity", &val);
-	reg |= val << TUSB1210_VENDOR_SPECIFIC2_DP_SHIFT;
+	if (!device_property_read_u8(&ulpi->dev, "datapolarity", &val))
+		u8p_replace_bits(&reg, val, (u8)TUSB1210_VENDOR_SPECIFIC2_DP_MASK);
 
-	if (reg) {
-		ulpi_write(ulpi, TUSB1210_VENDOR_SPECIFIC2, reg);
-		tusb->vendor_specific2 = reg;
-	}
+	ulpi_write(ulpi, TUSB1210_VENDOR_SPECIFIC2, reg);
+	tusb->vendor_specific2 = reg;
 
 	tusb->phy = ulpi_phy_create(ulpi, &phy_ops);
 	if (IS_ERR(tusb->phy))