mb/ocp/tiogapass: Properly configure early serial output

Tioga Pass comes with AST2500 BMC which offers SuperIO functionality.
However we currently do not configure/enable SuperIO chip. As a result
system boots pretty silently on cold boot. Then FSP configures SuperIO
and resets the system so on next boot serial console does work. This
makes debugging difficult because pre-FSP output is invisible.

This patch enables bootblock to properly configure desired BMC SuperIO
port so early serial output is visible.

TEST=do a cold boot on OCP Tioga Pass, observe bootblock output starting
from bootblock.

Change-Id: Iff8e6a862858d733f529bb9b8c65e22e5ec6b521
Signed-off-by: Andrey Petrov <anpetrov@fb.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/39782
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Maxim Polyakov <max.senia.poliak@gmail.com>

src/mainboard/ocp/tiogapass/Kconfig

@@ -22,6 +22,7 @@ config BOARD_SPECIFIC_OPTIONS
 	select MAINBOARD_USES_FSP2_0
 	select IPMI_KCS
 	select SOC_INTEL_SKYLAKE_SP
+	select SUPERIO_ASPEED_AST2400
 
 config MAINBOARD_DIR
 	string

src/mainboard/ocp/tiogapass/Makefile.inc

@@ -13,6 +13,7 @@
 ## GNU General Public License for more details.
 ##
 
+bootblock-y += bootblock.c
 ramstage-y += ramstage.c
 ramstage-$(CONFIG_HAVE_ACPI_TABLES) += fadt.c
 

src/mainboard/ocp/tiogapass/bootblock.c

@@ -0,0 +1,59 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/* This file is part of the coreboot project. */
+
+#include <bootblock_common.h>
+#include <device/pci_def.h>
+#include <device/pci_ops.h>
+#include <intelblocks/pcr.h>
+#include <soc/pci_devs.h>
+#include <soc/pcr_ids.h>
+#include <superio/aspeed/ast2400/ast2400.h>
+#include <superio/aspeed/common/aspeed.h>
+
+/* these are defined in intelblocks/lpc_lib.h but we can't use them yet */
+#define PCR_DMI_LPCIOD 0x2770
+#define PCR_DMI_LPCIOE 0x2774
+
+static void enable_espi_lpc_io_windows(void)
+{
+	/*
+	 * Set up decoding windows on PCH over PCR. The CPUs use two of AST2500 SIO ports,
+	 * one is connected to debug header (SUART1) and another is used as SOL (SUART2).
+	 * For that end it is wired into BMC virtual port.
+	 */
+
+	/* Open IO windows: 0x3f8 for com1 and 02e8 for com2 */
+	pcr_or32(PID_DMI, PCR_DMI_LPCIOD, (0 << 0) | (1 << 4));
+	/* LPC I/O enable: com1 and com2 */
+	pcr_or32(PID_DMI, PCR_DMI_LPCIOE, (1 << 0) | (1 << 1));
+
+	/* Enable com1 (0x3f8), com2 (02f8) and superio (0x2e) */
+	pci_mmio_write_config32(PCH_DEV_LPC, 0x80,
+		(1<<28) | (1<<16) | (1<<17) | (0 << 0) | (1 << 4));
+}
+
+static uint8_t com_to_ast_sio(uint8_t com)
+{
+	switch (com) {
+	case 0:
+		return AST2400_SUART1;
+	case 1:
+		return AST2400_SUART2;
+	case 2:
+		return AST2400_SUART3;
+	case 4:
+		return AST2400_SUART4;
+	default:
+		return AST2400_SUART1;
+	}
+}
+
+void bootblock_mainboard_early_init(void)
+{
+	/* Open IO windows */
+	enable_espi_lpc_io_windows();
+
+	/* Configure appropriate physical port of SuperIO chip off BMC */
+	const pnp_devfn_t serial_dev = PNP_DEV(0x2e, com_to_ast_sio(CONFIG_UART_FOR_CONSOLE));
+	aspeed_enable_serial(serial_dev, CONFIG_TTYS0_BASE);
+}