From e27e1c1c6389e0a4d87c97dfef14068bfc7ddde6 Mon Sep 17 00:00:00 2001
From: Tim Chu <Tim.Chu@quantatw.com>
Date: Wed, 19 Oct 2022 06:24:21 +0000
Subject: [PATCH] soc/intel/xeon_sp: Add functions to store/restore uart state
 in smm

When CONFIG_DEBUG_SMI is enabled SMM handler performs console hardware
initialization that may interfere with OS. Here we store the state
before console initialization and restore state before SMM exit.

Tested=On not public yet system, after exiting smm, uart console can
still work well.

Signed-off-by: Tim Chu <Tim.Chu@quantatw.com>
Change-Id: Ifa5042c24f0e3217a75971d9e6067b1d1f56a484
Reviewed-on: https://review.coreboot.org/c/coreboot/+/68567
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Jonathan Zhang <jonzhang@fb.com>
---
 src/soc/intel/xeon_sp/smihandler.c | 43 ++++++++++++++++++++++++++++++
 1 file changed, 43 insertions(+)

diff --git a/src/soc/intel/xeon_sp/smihandler.c b/src/soc/intel/xeon_sp/smihandler.c
index 1c04b95d73..d644447aee 100644
--- a/src/soc/intel/xeon_sp/smihandler.c
+++ b/src/soc/intel/xeon_sp/smihandler.c
@@ -1,12 +1,55 @@
 /* SPDX-License-Identifier: GPL-2.0-only */
 
+#include <arch/io.h>
 #include <console/console.h>
+#include <console/uart.h>
 #include <cpu/x86/smm.h>
 #include <device/pci.h>
+#include <drivers/uart/uart8250reg.h>
 #include <intelblocks/smihandler.h>
 #include <soc/pci_devs.h>
 #include <soc/pm.h>
 
+struct uart8250_state {
+	uint8_t IER, IIR, MCR, LCR, DLL, DLM;
+};
+
+static struct uart8250_state s_uart8250_state;
+
+static void uart8250_store(unsigned int base_port)
+{
+	/* Save previous state for restoring later. */
+	s_uart8250_state.IER = inb(base_port + UART8250_IER);
+	s_uart8250_state.IIR = inb(base_port + UART8250_FCR);
+	s_uart8250_state.MCR = inb(base_port + UART8250_MCR);
+	s_uart8250_state.LCR = inb(base_port + UART8250_LCR);
+	s_uart8250_state.DLL = inb(base_port + UART8250_DLL);
+	s_uart8250_state.DLM = inb(base_port + UART8250_DLM);
+}
+
+void smm_soc_early_init(void)
+{
+	if (CONFIG(DRIVERS_UART_8250IO) && CONFIG(DEBUG_SMI))
+		uart8250_store(uart_platform_base(CONFIG_UART_FOR_CONSOLE));
+}
+
+static void uart8250_restore(unsigned int base_port)
+{
+	outb(s_uart8250_state.DLL, base_port + UART8250_DLL);
+	outb(s_uart8250_state.DLM, base_port + UART8250_DLM);
+	outb(s_uart8250_state.MCR, base_port + UART8250_MCR);
+	outb(s_uart8250_state.LCR, base_port + UART8250_LCR);
+	if ((s_uart8250_state.IIR & UART8250_IIR_FIFO_EN) == UART8250_IIR_FIFO_EN)
+		outb(UART8250_FCR_FIFO_EN, base_port + UART8250_FCR);
+	outb(s_uart8250_state.IER, base_port + UART8250_IER);
+}
+
+void smm_soc_exit(void)
+{
+	if (CONFIG(DRIVERS_UART_8250IO) && CONFIG(DEBUG_SMI))
+		uart8250_restore(uart_platform_base(CONFIG_UART_FOR_CONSOLE));
+}
+
 /*
  * Specific SOC SMI handler during ramstage finalize phase
  */