x86: chromebook_link: Enable the debug UART

Add support for the debug UART on link. This is useful for early debugging.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>

arch/x86/cpu/ivybridge/cpu.c

@@ -340,3 +340,10 @@ int print_cpuinfo(void)
 
 	return 0;
 }
+
+void board_debug_uart_init(void)
+{
+	/* This enables the debug UART */
+	pci_x86_write_config(NULL, PCH_LPC_DEV, LPC_EN, COMA_LPC_EN,
+			     PCI_SIZE_16);
+}

configs/chromebook_link_defconfig

@@ -22,6 +22,10 @@ CONFIG_CROS_EC_LPC=y
 CONFIG_SPI_FLASH=y
 CONFIG_DM_PCI=y
 CONFIG_DM_RTC=y
+CONFIG_DEBUG_UART=y
+CONFIG_DEBUG_UART_BASE=0x3f8
+CONFIG_DEBUG_UART_CLOCK=1843200
+CONFIG_DEBUG_UART_BOARD_INIT=y
 CONFIG_DM_TPM=y
 CONFIG_TPM_TIS_LPC=y
 CONFIG_VIDEO_VESA=y