soc/amd/stoneyridge: initialize GPIOs for serial console

Initialize the two GPIOs of the SoC UART if it's used for serial console
to be sure that the I/O mux is configured correctly without having to
rely on the bootblock_mainboard_early_init call to do this. This brings
Stoneyridge more in line with the other AMD SoCs. Since this code will
be factored out to the common AMD SoC code in a follow-up patch, the
function prototype is added to southbridge.h instead of creating a new
uart.h header file.

Signed-off-by: Felix Held <felix-coreboot@felixheld.de>
Change-Id: Id4aa6734e63dad204d22ce962b983cde6e3abd62
Reviewed-on: https://review.coreboot.org/c/coreboot/+/68533
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Fred Reitberger <reitbergerfred@gmail.com>

src/soc/amd/stoneyridge/early_fch.c

@@ -127,6 +127,9 @@ void bootblock_fch_early_init(void)
 	fch_enable_legacy_io();
 	enable_aoac_devices();
 
+	if (CONFIG(AMD_SOC_CONSOLE_UART))
+		set_uart_config(CONFIG_UART_FOR_CONSOLE);
+
 	/* disable the keyboard reset function before mainboard GPIO setup */
 	if (CONFIG(DISABLE_KEYBOARD_RESET_PIN))
 		fch_disable_kb_rst();

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

@@ -184,6 +184,8 @@ void fch_final(void *chip_info);
 void enable_aoac_devices(void);
 void fch_clk_output_48Mhz(u32 osc);
 
+void set_uart_config(unsigned int idx);
+
 /*
  * Call the mainboard to get the USB Over Current Map. The mainboard
  * returns the map and 0 on Success or -1 on error or no map. There is

src/soc/amd/stoneyridge/uart.c

@@ -6,6 +6,7 @@
 #include <soc/aoac_defs.h>
 #include <soc/gpio.h>
 #include <soc/iomap.h>
+#include <soc/southbridge.h>
 #include <types.h>
 
 static const struct soc_uart_ctrlr_info uart_info[] = {
@@ -26,3 +27,11 @@ uintptr_t get_uart_base(unsigned int idx)
 
 	return uart_info[idx].base;
 }
+
+void set_uart_config(unsigned int idx)
+{
+	if (idx >= ARRAY_SIZE(uart_info))
+		return;
+
+	gpio_configure_pads(uart_info[idx].mux, 2);
+}