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From:   Parthiban Veerasooran <Parthiban.Veerasooran@microchip.com>
To:     <andrew@lunn.ch>, <hkallweit1@gmail.com>, <linux@armlinux.org.uk>,
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CC:     <horatiu.vultur@microchip.com>, <Woojung.Huh@microchip.com>,
        <Nicolas.Ferre@microchip.com>, <Thorsten.Kummermehr@microchip.com>,
        "Parthiban Veerasooran" <Parthiban.Veerasooran@microchip.com>
Subject: [PATCH net-next v4 2/6] net: phy: microchip_t1s: replace read-modify-write code with phy_modify_mmd
Date:   Fri, 26 May 2023 20:53:44 +0530
Message-ID: <20230526152348.70781-3-Parthiban.Veerasooran@microchip.com>
In-Reply-To: <20230526152348.70781-1-Parthiban.Veerasooran@microchip.com>
References: <20230526152348.70781-1-Parthiban.Veerasooran@microchip.com>
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Replace read-modify-write code in the lan867x_config_init function to
avoid handling data type mismatch and to simplify the code.

Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Parthiban Veerasooran <Parthiban.Veerasooran@microchip.com>
---
 drivers/net/phy/microchip_t1s.c | 41 +++++++++++----------------------
 1 file changed, 13 insertions(+), 28 deletions(-)

diff --git a/drivers/net/phy/microchip_t1s.c b/drivers/net/phy/microchip_t1s.c
index a42a6bb6e3bd..fd27e94c9ee5 100644
--- a/drivers/net/phy/microchip_t1s.c
+++ b/drivers/net/phy/microchip_t1s.c
@@ -31,19 +31,19 @@
  * W   0x1F 0x0099 0x7F80 ------
  */
 
-static const int lan867x_fixup_registers[12] = {
+static const u32 lan867x_fixup_registers[12] = {
 	0x00D0, 0x00D1, 0x0084, 0x0085,
 	0x008A, 0x0087, 0x0088, 0x008B,
 	0x0080, 0x00F1, 0x0096, 0x0099,
 };
 
-static const int lan867x_fixup_values[12] = {
+static const u16 lan867x_fixup_values[12] = {
 	0x0002, 0x0000, 0x3380, 0x0006,
 	0xC000, 0x801C, 0x033F, 0x0404,
 	0x0600, 0x2400, 0x2000, 0x7F80,
 };
 
-static const int lan867x_fixup_masks[12] = {
+static const u16 lan867x_fixup_masks[12] = {
 	0x0E03, 0x0300, 0xFFC0, 0x000F,
 	0xF800, 0x801C, 0x1FFF, 0xFFFF,
 	0x0600, 0x7F00, 0x2000, 0xFFFF,
@@ -51,35 +51,20 @@ static const int lan867x_fixup_masks[12] = {
 
 static int lan867x_config_init(struct phy_device *phydev)
 {
-	/* HW quirk: Microchip states in the application note (AN1699) for the phy
-	 * that a set of read-modify-write (rmw) operations has to be performed
-	 * on a set of seemingly magic registers.
-	 * The result of these operations is just described as 'optimal performance'
-	 * Microchip gives no explanation as to what these mmd regs do,
-	 * in fact they are marked as reserved in the datasheet.
-	 * It is unclear if phy_modify_mmd would be safe to use or if a write
-	 * really has to happen to each register.
-	 * In order to exactly conform to what is stated in the AN phy_write_mmd is
-	 * used, which might then write the same value back as read + modified.
-	 */
-
-	int reg_value;
 	int err;
-	int reg;
 
-	/* Read-Modified Write Pseudocode (from AN1699)
-	 * current_val = read_register(mmd, addr) // Read current register value
-	 * new_val = current_val AND (NOT mask) // Clear bit fields to be written
-	 * new_val = new_val OR value // Set bits
-	 * write_register(mmd, addr, new_val) // Write back updated register value
+	/* Reference to AN1699
+	 * https://ww1.microchip.com/downloads/aemDocuments/documents/AIS/ProductDocuments/SupportingCollateral/AN-LAN8670-1-2-config-60001699.pdf
+	 * AN1699 says Read, Modify, Write, but the Write is not required if the
+	 * register already has the required value. So it is safe to use
+	 * phy_modify_mmd here.
 	 */
 	for (int i = 0; i < ARRAY_SIZE(lan867x_fixup_registers); i++) {
-		reg = lan867x_fixup_registers[i];
-		reg_value = phy_read_mmd(phydev, MDIO_MMD_VEND2, reg);
-		reg_value &= ~lan867x_fixup_masks[i];
-		reg_value |= lan867x_fixup_values[i];
-		err = phy_write_mmd(phydev, MDIO_MMD_VEND2, reg, reg_value);
-		if (err != 0)
+		err = phy_modify_mmd(phydev, MDIO_MMD_VEND2,
+				     lan867x_fixup_registers[i],
+				     lan867x_fixup_masks[i],
+				     lan867x_fixup_values[i]);
+		if (err)
 			return err;
 	}
 
-- 
2.34.1