mb/*/*/romstage.c: Clean up targets with i82801gx

Things cleaned up in this patch:
* Add macros for the GENx_DEC registers;
* replace many magic numbers by macros;
* remove many writes to DxxIP since they were 'setting' reset default
  values;
* fix some comments about decode ranges.

Change-Id: I9d6a0ff3d391947f611a2f3c65684f4ee57bc263
Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-on: https://review.coreboot.org/21065
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
diff --git a/src/mainboard/getac/p470/romstage.c b/src/mainboard/getac/p470/romstage.c
index d1552a65..e58ef1b 100644
--- a/src/mainboard/getac/p470/romstage.c
+++ b/src/mainboard/getac/p470/romstage.c
@@ -57,21 +57,23 @@
 static void ich7_enable_lpc(void)
 {
 	int lpt_en = 0;
-	if (read_option(lpt, 0) != 0) {
-	       lpt_en = 1 << 2; // enable LPT
-	}
+	if (read_option(lpt, 0) != 0)
+		lpt_en = LPT_LPC_EN;
+
 	// Enable Serial IRQ
-	pci_write_config8(PCI_DEV(0, 0x1f, 0), 0x64, 0xd0);
+	pci_write_config8(PCI_DEV(0, 0x1f, 0), SERIRQ_CNTL, 0xd0);
 	// decode range
-	pci_write_config16(PCI_DEV(0, 0x1f, 0), 0x80, 0x0007);
+	pci_write_config16(PCI_DEV(0, 0x1f, 0), LPC_IO_DEC, 0x0007);
 	// decode range
-	pci_write_config16(PCI_DEV(0, 0x1f, 0), 0x82, 0x3f0b | lpt_en);
+	pci_write_config16(PCI_DEV(0, 0x1f, 0), LPC_EN, CNF2_LPC_EN | CNF1_LPC_EN
+			| MC_LPC_EN | KBC_LPC_EN | GAMEH_LPC_EN | GAMEL_LPC_EN
+			| FDD_LPC_EN| lpt_en | COMB_LPC_EN | COMA_LPC_EN);
 	// Enable 0x02e0 - 0x2ff
-	pci_write_config32(PCI_DEV(0, 0x1f, 0), 0x84, 0x001c02e1);
+	pci_write_config32(PCI_DEV(0, 0x1f, 0), GEN1_DEC, 0x001c02e1);
 	// Enable 0x600 - 0x6ff
-	pci_write_config32(PCI_DEV(0, 0x1f, 0), 0x88, 0x00fc0601);
+	pci_write_config32(PCI_DEV(0, 0x1f, 0), GEN2_DEC, 0x00fc0601);
 	// Enable 0x68 - 0x6f
-	pci_write_config32(PCI_DEV(0, 0x1f, 0), 0x8c, 0x00040069);
+	pci_write_config32(PCI_DEV(0, 0x1f, 0), GEN3_DEC, 0x00040069);
 }
 
 /* This box has two superios, so enabling serial becomes slightly excessive.
@@ -150,23 +152,23 @@
 	//RCBA32(0x001c) = 0x03128010;
 
 	/* Device 1f interrupt pin register */
-	RCBA32(0x3100) = 0x00042220;
+	RCBA32(D31IP) = 0x00042220;
 	/* Device 1d interrupt pin register */
-	RCBA32(0x310c) = 0x00214321;
+	RCBA32(D28IP) = 0x00214321;
 
 	/* dev irq route register */
-	RCBA16(0x3140) = 0x0232;
-	RCBA16(0x3142) = 0x3246;
-	RCBA16(0x3144) = 0x0237;
-	RCBA16(0x3146) = 0x3201;
-	RCBA16(0x3148) = 0x3216;
+	RCBA16(D31IR) = 0x0232;
+	RCBA16(D30IR) = 0x3246;
+	RCBA16(D29IR) = 0x0237;
+	RCBA16(D28IR) = 0x3201;
+	RCBA16(D27IR) = 0x3216;
 
 	/* Enable IOAPIC */
-	RCBA8(0x31ff) = 0x03;
+	RCBA8(OIC) = 0x03;
 
 	/* Disable unused devices */
-	RCBA32(0x3418) = FD_PCIE6 | FD_PCIE5 | FD_INTLAN | FD_ACMOD | FD_ACAUD | FD_PATA;
-	RCBA32(0x3418) |= (1 << 0); // Required.
+	RCBA32(FD) = FD_PCIE6 | FD_PCIE5 | FD_INTLAN | FD_ACMOD | FD_ACAUD | FD_PATA;
+	RCBA32(FD) |= (1 << 0); // Required.
 
 	/* Enable PCIe Root Port Clock Gate */
 	// RCBA32(0x341c) = 0x00000001;
@@ -221,7 +223,7 @@
 	reg32 &= ~(3 << 0);
 	reg32 |= (1 << 0);
 	RCBA32(0x3430) = reg32;
-	RCBA32(0x3418) |= (1 << 0);
+	RCBA32(FD) |= (1 << 0);
 	RCBA16(0x0200) = 0x2008;
 	RCBA8(0x2027) = 0x0d;
 	RCBA16(0x3e08) |= (1 << 7);