sata_mv: PHY_MODE4 cleanups

The handling for PHY_MODE4 was originally just cloned from the
Marvell proprietary driver (with their blessing).
But we can do better than that.

Tidy things up with some judicious mask definitions, to improve maintainability.
Signed-off-by: Mark Lord <mlord@pobox.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>

drivers/ata/sata_mv.c

@@ -224,6 +224,11 @@ enum {
 
 	PHY_MODE3		= 0x310,
 	PHY_MODE4		= 0x314,
+	PHY_MODE4_CFG_MASK	= 0x00000003,	/* phy internal config field */
+	PHY_MODE4_CFG_VALUE	= 0x00000001,	/* phy internal config field */
+	PHY_MODE4_RSVD_ZEROS	= 0x5de3fffa,	/* Gen2e always write zeros */
+	PHY_MODE4_RSVD_ONES	= 0x00000005,	/* Gen2e always write ones */
+
 	PHY_MODE2		= 0x330,
 	SATA_IFCTL_OFS		= 0x344,
 	SATA_TESTCTL_OFS	= 0x348,
@@ -2563,17 +2568,16 @@ static void mv6_phy_errata(struct mv_host_priv *hpriv, void __iomem *mmio,
 		m3 &= ~0x1c;
 
 	if (fix_phy_mode4) {
-		u32 m4;
-
-		m4 = readl(port_mmio + PHY_MODE4);
-
-		/* workaround for errata FEr SATA#10 (part 1) */
-		m4 = (m4 & ~(1 << 1)) | (1 << 0);
-
-		/* enforce bit restrictions on GenIIe devices */
+		u32 m4 = readl(port_mmio + PHY_MODE4);
+		/*
+		 * Enforce reserved-bit restrictions on GenIIe devices only.
+		 * For earlier chipsets, force only the internal config field
+		 *  (workaround for errata FEr SATA#10 part 1).
+		 */
 		if (IS_GEN_IIE(hpriv))
-			m4 = (m4 & ~0x5DE3FFFC) | (1 << 2);
-
+			m4 = (m4 & ~PHY_MODE4_RSVD_ZEROS) | PHY_MODE4_RSVD_ONES;
+		else
+			m4 = (m4 & ~PHY_MODE4_CFG_MASK) | PHY_MODE4_CFG_VALUE;
 		writel(m4, port_mmio + PHY_MODE4);
 	}
 	/*