amd/agesa: Make BottomIo position configurable

Some PCI peripherals, such as discrete VGA adapters, require a great
amount of memory mapped IO. This patch allows the user to select at
build time the bottom IO to leave enough space for such devices.

We cannot calculate this value at runtime because it has to be set
before the PCI devices are enumerated. 0x80000000 has been successfully
boot-tested on A88XM-E (fam15tn), G505S (fam15tn) and AM1I-A (fam16kb).

Signed-off-by: Mike Banon <mikebdp2@gmail.com>
Change-Id: Ie235631231bcb4aeebaff2e0026da2ea9d82f9d0
Reviewed-on: https://review.coreboot.org/c/coreboot/+/38472
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Michał Żygowski <michal.zygowski@3mdeb.com>

src/northbridge/amd/agesa/Kconfig

@@ -19,6 +19,17 @@ config NORTHBRIDGE_AMD_AGESA
 
 if NORTHBRIDGE_AMD_AGESA
 
+config BOTTOMIO_POSITION
+	hex "Bottom of 32-bit IO space"
+	default 0x80000000
+	help
+	  If PCI peripherals with big BARs are connected to the system
+	  the bottom of the IO must be decreased to allocate such devices.
+
+	  Declare the beginning of the 128MB-aligned MMIO region.  This
+	  option is useful when PCI peripherals requesting large address
+	  ranges are present, for example, graphic cards.
+
 config CONSOLE_VGA_MULTI
 	bool
 	default n

src/northbridge/amd/agesa/family14/state_machine.c

@@ -48,6 +48,8 @@ void platform_BeforeInitEarly(struct sysinfo *cb, AMD_EARLY_PARAMS *Early)
 
 void platform_BeforeInitPost(struct sysinfo *cb, AMD_POST_PARAMS *Post)
 {
+	Post->MemConfig.BottomIo = (UINT16)(MIN(0xE0000000,
+			MAX(0x28000000, CONFIG_BOTTOMIO_POSITION)) >> 24) & 0xF8;
 }
 
 void platform_AfterInitPost(struct sysinfo *cb, AMD_POST_PARAMS *Post)

src/northbridge/amd/agesa/family15tn/state_machine.c

@@ -18,6 +18,8 @@ void platform_BeforeInitEarly(struct sysinfo *cb, AMD_EARLY_PARAMS *Early)
 
 void platform_BeforeInitPost(struct sysinfo *cb, AMD_POST_PARAMS *Post)
 {
+	Post->MemConfig.BottomIo = (UINT16)(MIN(0xE0000000,
+			MAX(0x28000000, CONFIG_BOTTOMIO_POSITION)) >> 24) & 0xF8;
 }
 
 void platform_AfterInitPost(struct sysinfo *cb, AMD_POST_PARAMS *Post)

src/northbridge/amd/agesa/family16kb/state_machine.c

@@ -20,6 +20,9 @@ void platform_BeforeInitPost(struct sysinfo *cb, AMD_POST_PARAMS *Post)
 {
 	AGESA_STATUS status;
 
+	Post->MemConfig.BottomIo = (UINT16)(MIN(0xE0000000,
+			MAX(0x28000000, CONFIG_BOTTOMIO_POSITION)) >> 24) & 0xF8;
+
 	if (CONFIG(ENABLE_MRC_CACHE)) {
 		status = OemInitResume(&Post->MemConfig.MemContext);
 		if (status == AGESA_SUCCESS)