[S] Change in coreboot[master]: soc/amd: Clarify ACPI _PRT entry generation

[Kyösti Mälkki (Code Review)]

Attention is currently required from: Jason Glenesk, Raul Rangel, Matt DeVillier, Fred Reitberger, Felix Held.

Kyösti Mälkki has uploaded this change for review. ( https://review.coreboot.org/c/coreboot/+/74314 )

Change subject: soc/amd: Clarify ACPI _PRT entry generation
......................................................................

soc/amd: Clarify ACPI _PRT entry generation

The reference to a constant FCH IOAPIC interrupt count used
with GNB IOAPIC was a bit obscure.

Change-Id: I2d862e37424f9fea7f269cd09e9e90056531b643
Signed-off-by: Kyösti Mälkki 
---
M src/arch/x86/include/arch/ioapic.h
M src/soc/amd/common/block/pci/acpi_prt.c
2 files changed, 19 insertions(+), 5 deletions(-)

git pull ssh://review.coreboot.org:29418/coreboot refs/changes/14/74314/1

diff --git a/src/arch/x86/include/arch/ioapic.h b/src/arch/x86/include/arch/ioapic.h
index a91ac14..6c5282b 100644
--- a/src/arch/x86/include/arch/ioapic.h
+++ b/src/arch/x86/include/arch/ioapic.h
@@ -5,7 +5,6 @@

#define IO_APIC_ADDR	0xfec00000
 #define VIO_APIC_VADDR	((u8 *)IO_APIC_ADDR)
-#define IO_APIC_INTERRUPTS 24

#ifndef __ACPI__

diff --git a/src/soc/amd/common/block/pci/acpi_prt.c b/src/soc/amd/common/block/pci/acpi_prt.c
index c142f57..f748024 100644
--- a/src/soc/amd/common/block/pci/acpi_prt.c
+++ b/src/soc/amd/common/block/pci/acpi_prt.c
@@ -7,20 +7,22 @@
 #include <arch/ioapic.h>
 #include <device/device.h>

+/* GNB IO-APIC is located after the FCH IO-APIC */
+#define FCH_IOAPIC_INTERRUPTS	24
+#define GNB_GSI_BASE		FCH_IOAPIC_INTERRUPTS
+
 static void acpigen_write_PRT_GSI(const struct pci_routing_info *routing_info)
 {
    unsigned int irq;

acpigen_write_package(4); /* Package - APIC Routing */
    for (unsigned int i = 0; i < 4; ++i) {
-		/* GNB IO-APIC is located after the FCH IO-APIC */
-		irq = IO_APIC_INTERRUPTS;
-		irq += pci_calculate_irq(routing_info, i);
+		irq = pci_calculate_irq(routing_info, i);

acpigen_write_PRT_GSI_entry(
    		0, /* There is only one device attached to the bridge */
    		i, /* pin */
-			irq);
+			GNB_GSI_BASE + irq);
    }
    acpigen_pop_len(); /* Package - APIC Routing */
 }