soc/amd/cezanne/psp_verstage: Implement get_uart_base

This will allow directly using the UART console. On PSP releases that
don't support mapping the UART, we will just return NULL which is
perfectly acceptable.

BUG=b:215599230
TEST=Boot guybrush and verify verstage can print to the console

Signed-off-by: Raul E Rangel <rrangel@chromium.org>
Change-Id: Ic8d7f0fe00794a715756f92e3fb32c6b512cb8aa
Reviewed-on: https://review.coreboot.org/c/coreboot/+/61607
Reviewed-by: Karthik Ramasubramanian <kramasub@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/soc/amd/cezanne/psp_verstage/Makefile.inc

@@ -9,6 +9,7 @@ subdirs-$(CONFIG_VBOOT_STARTS_BEFORE_BOOTBLOCK) += ../../common/psp_verstage
 
 verstage-y += svc.c
 verstage-y += chipset.c
+verstage-y += uart.c
 
 verstage-y += $(top)/src/vendorcode/amd/fsp/cezanne/bl_uapp/bl_uapp_startup.S
 verstage-y += $(top)/src/vendorcode/amd/fsp/cezanne/bl_uapp/bl_uapp_end.S

src/soc/amd/cezanne/psp_verstage/uart.c

@@ -0,0 +1,26 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#include <bl_uapp/bl_syscall_public.h>
+#include <amdblocks/uart.h>
+#include <types.h>
+
+static void *uart_bars[FCH_UART_ID_MAX - 1];
+
+uintptr_t get_uart_base(unsigned int idx)
+{
+	uint32_t err;
+
+	if (idx > ARRAY_SIZE(uart_bars))
+		return 0;
+
+	if (uart_bars[idx])
+		return (uintptr_t)uart_bars[idx];
+
+	err = svc_map_fch_dev(FCH_IO_DEVICE_UART, idx, 0, &uart_bars[idx]);
+	if (err) {
+		svc_debug_print("Failed to map UART\n");
+		return 0;
+	}
+
+	return (uintptr_t)uart_bars[idx];
+}