nb/intel/i945: Deduplicate PCIEXBAR decoding

We can use `decode_pcie_bar` instead, if we make it non-static.

Change-Id: Ic39f3df0293b4d44f031515b1f868e0bb9f750c9
Signed-off-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/44145
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>

src/northbridge/intel/i945/acpi.c

@@ -3,46 +3,19 @@
 #include <types.h>
 #include <acpi/acpi.h>
 #include <acpi/acpigen.h>
+#include <commonlib/helpers.h>
 #include <device/device.h>
 #include <device/pci_ops.h>
 #include "i945.h"
 
 unsigned long acpi_fill_mcfg(unsigned long current)
 {
-	struct device *dev;
+	u32 length, pciexbar;
-	u32 pciexbar = 0;
-	u32 pciexbar_reg;
-	int max_buses;
 
-	dev = pcidev_on_root(0, 0);
+	if (!decode_pcie_bar(&pciexbar, &length))
-	if (!dev)
 		return current;
 
-	pciexbar_reg = pci_read_config32(dev, PCIEXBAR);
+	const int max_buses = length / MiB;
-
-	// MMCFG not supported or not enabled.
-	if (!(pciexbar_reg & (1 << 0)))
-		return current;
-
-	switch ((pciexbar_reg >> 1) & 3) {
-	case 0: // 256MB
-		pciexbar = pciexbar_reg & ((1 << 31)|(1 << 30)|(1 << 29)|(1 << 28));
-		max_buses = 256;
-		break;
-	case 1: // 128M
-		pciexbar = pciexbar_reg & ((1 << 31)|(1 << 30)|(1 << 29)|(1 << 28)|(1 << 27));
-		max_buses = 128;
-		break;
-	case 2: // 64M
-		pciexbar = pciexbar_reg & ((1 << 31)|(1 << 30)|(1 << 29)|(1 << 28)|(1 << 27)|(1 << 26));
-		max_buses = 64;
-		break;
-	default: // RSVD
-		return current;
-	}
-
-	if (!pciexbar)
-		return current;
 
 	current += acpi_create_mcfg_mmconfig((acpi_mcfg_mmconfig_t *) current,
 			pciexbar, 0x0, 0x0, max_buses - 1);

src/northbridge/intel/i945/i945.h

@@ -364,6 +364,8 @@ void sdram_dump_mchbar_registers(void);
 u32 decode_igd_memory_size(u32 gms);
 u32 decode_tseg_size(const u8 esmramc);
 
+int decode_pcie_bar(u32 *const base, u32 *const len);
+
 /* Romstage mainboard callbacks */
 /* Optional: Override the default LPC config. */
 void mainboard_lpc_decode(void);

src/northbridge/intel/i945/northbridge.c

@@ -12,7 +12,7 @@
 #include <cpu/intel/smm_reloc.h>
 #include "i945.h"
 
-static int decode_pcie_bar(u32 *const base, u32 *const len)
+int decode_pcie_bar(u32 *const base, u32 *const len)
 {
 	*base = 0;
 	*len = 0;