amd/stoneyridge: Convert BiosRam access to MMIO

Change the BiosRam read/write functions to use the fixed MMIO range at
0xfed80500.  This is faster than two accesses per byte when using I/O
0xcd4/0xcd5.

Note that BiosRam may only be accessed byte-by-byte.  It does not decode
normally.

Change-Id: I9d8baf2bd5d9d48a87bddfb6a0b86e292a8fdf7d
Signed-off-by: Marshall Dawson <marshalldawson3rd@gmail.com>
Reviewed-on: https://review.coreboot.org/23436
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Kyösti Mälkki <kyosti.malkki@gmail.com>

src/soc/amd/stoneyridge/include/soc/iomap.h

@@ -36,6 +36,7 @@
 #define AMD_SB_ACPI_MMIO_ADDR		0xfed80000
 #define APU_SMI_BASE			0xfed80200
 #define PM_MMIO_BASE			0xfed80300
+#define BIOSRAM_MMIO_BASE		0xfed80500
 #define XHCI_ACPI_PM_MMIO_BASE		0xfed81c00
 #define APU_UART0_BASE			0xfedc6000
 #define APU_UART1_BASE			0xfedc8000

src/soc/amd/stoneyridge/sb_util.c

@@ -78,16 +78,15 @@ void smi_write8(uint8_t offset, uint8_t value)
 
 uint8_t biosram_read8(uint8_t offset)
 {
-	outb(offset, BIOSRAM_INDEX);
-	return inb(BIOSRAM_DATA);
+	return read8((void *)(BIOSRAM_MMIO_BASE + offset));
 }
 
 void biosram_write8(uint8_t offset, uint8_t value)
 {
-	outb(offset, BIOSRAM_INDEX);
-	outb(value, BIOSRAM_DATA);
+	write8((void *)(BIOSRAM_MMIO_BASE + offset), value);
 }
 
+/* BiosRam may only be accessed a byte at a time */
 uint16_t biosram_read16(uint8_t offset)
 {
 	int i;