sb/intel/lynxpoint: Add SerialIO UART console support

Derived from Broadwell and adapted to follow what soc/intel does. Note
that SERIALIO_UART_CONSOLE is meant to be selected from the mainboards
which expose a SerialIO UART. UART_FOR_CONSOLE also needs to be set in
mainboard Kconfig accordingly.

It is possible that some of the UART configuration steps in bootblock
are unnecessary. However, some of the steps turn off power management
features and others are undocumented: omitting them could cause weird
issues.

Finally, add a config file to ensure the code gets build-tested.

Tested on out-of-tree Compal LA-A992P, SerialIO UART 0 can be used to
receive coreboot and SeaBIOS logs.

Change-Id: Ifb3460dd50ed03421a38f03c80f91ae9fd604022
Signed-off-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/52489
Reviewed-by: Nico Huber <nico.h@gmx.de>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

7 files changed, 120 insertions, 3 deletions

diff --git a/src/southbridge/intel/lynxpoint/Kconfig b/src/southbridge/intel/lynxpoint/Kconfig
index a9a2f5bb9e..fe859f62ed 100644
--- a/src/southbridge/intel/lynxpoint/Kconfig
+++ b/src/southbridge/intel/lynxpoint/Kconfig
@@ -68,4 +68,15 @@ config PCIEXP_AER
 	bool
 	default y
 
+config SERIALIO_UART_CONSOLE
+	bool "Use SerialIO UART for console"
+	depends on INTEL_LYNXPOINT_LP
+	select DRIVERS_UART_8250MEM_32
+	help
+	  Selected by mainboards where SerialIO UARTs can be used to retrieve
+	  coreboot logs. Boards also need to set UART_FOR_CONSOLE accordingly.
+
+config CONSOLE_UART_BASE_ADDRESS
+	default 0xd6000000 if SERIALIO_UART_CONSOLE
+
 endif
diff --git a/src/southbridge/intel/lynxpoint/Makefile.inc b/src/southbridge/intel/lynxpoint/Makefile.inc
index 2923035e1e..02022d348d 100644
--- a/src/southbridge/intel/lynxpoint/Makefile.inc
+++ b/src/southbridge/intel/lynxpoint/Makefile.inc
@@ -42,6 +42,10 @@ romstage-y += lp_gpio.c
 ramstage-y += lp_gpio.c
 smm-y += lp_gpio.c
 verstage-y += lp_gpio.c
+bootblock-$(CONFIG_SERIALIO_UART_CONSOLE) += uart_init.c
+bootblock-$(CONFIG_SERIALIO_UART_CONSOLE) += iobp.c
+all-$(CONFIG_SERIALIO_UART_CONSOLE) += uart.c
+smm-$(CONFIG_SERIALIO_UART_CONSOLE) += uart.c
 endif
 
 verstage-y += pmutil.c
diff --git a/src/southbridge/intel/lynxpoint/bootblock.c b/src/southbridge/intel/lynxpoint/bootblock.c
index c063bfb10a..495871c6d2 100644
--- a/src/southbridge/intel/lynxpoint/bootblock.c
+++ b/src/southbridge/intel/lynxpoint/bootblock.c
@@ -51,4 +51,7 @@ void bootblock_early_southbridge_init(void)
 
 	pch_enable_lpc();
 	mainboard_config_superio();
+
+	if (CONFIG(SERIALIO_UART_CONSOLE))
+		uart_bootblock_init();
 }
diff --git a/src/southbridge/intel/lynxpoint/pch.h b/src/southbridge/intel/lynxpoint/pch.h
index 7b09d54f18..598c2dc7b2 100644
--- a/src/southbridge/intel/lynxpoint/pch.h
+++ b/src/southbridge/intel/lynxpoint/pch.h
@@ -157,6 +157,7 @@ void acpi_create_serialio_ssdt(acpi_header_t *ssdt);
 void enable_usb_bar(void);
 void early_pch_init(void);
 void pch_enable_lpc(void);
+void uart_bootblock_init(void);
 void mainboard_config_superio(void);
 void mainboard_config_rcba(void);
 
@@ -372,6 +373,9 @@ void mainboard_config_rcba(void);
 
 #define SIO_REG_PPR_CLOCK		0x800
 #define  SIO_REG_PPR_CLOCK_EN		 (1 << 0)
+#define  SIO_REG_PPR_CLOCK_UPDATE	 (1 << 31)
+#define  SIO_REG_PPR_CLOCK_M_DIV	 0x25a
+#define  SIO_REG_PPR_CLOCK_N_DIV	 0x7fff
 #define SIO_REG_PPR_RST			0x804
 #define  SIO_REG_PPR_RST_ASSERT		 0x3
 #define SIO_REG_PPR_GEN			0x808
diff --git a/src/southbridge/intel/lynxpoint/serialio.c b/src/southbridge/intel/lynxpoint/serialio.c
index 05263fec39..34f8c78c6d 100644
--- a/src/southbridge/intel/lynxpoint/serialio.c
+++ b/src/southbridge/intel/lynxpoint/serialio.c
@@ -8,6 +8,7 @@
 #include <device/pci.h>
 #include <device/pci_ids.h>
 #include <soc/nvs.h>
+#include <types.h>
 #include "chip.h"
 #include "iobp.h"
 #include "pch.h"
@@ -20,6 +21,19 @@ static void serialio_enable_clock(struct resource *bar0)
 	write32(res2mmio(bar0, SIO_REG_PPR_CLOCK, 0), reg32);
 }
 
+static bool serialio_uart_is_debug(struct device *dev)
+{
+	if (CONFIG(SERIALIO_UART_CONSOLE)) {
+		switch (dev->path.pci.devfn) {
+		case PCH_DEVFN_UART0:
+			return CONFIG_UART_FOR_CONSOLE == 0;
+		case PCH_DEVFN_UART1:
+			return CONFIG_UART_FOR_CONSOLE == 1;
+		}
+	}
+	return 0;
+}
+
 /* Put Serial IO D21:F0-F6 device into desired mode. */
 static void serialio_d21_mode(int sio_index, int int_pin, int acpi_mode)
 {
@@ -197,13 +211,15 @@ static void serialio_init(struct device *dev)
 		break;
 	case PCH_DEVFN_UART0: /* UART0 */
 		sio_index = SIO_ID_UART0;
-		serialio_d21_ltr(bar0);
+		if (!serialio_uart_is_debug(dev))
+			serialio_d21_ltr(bar0);
 		serialio_d21_mode(sio_index, SIO_PIN_INTD,
 				  config->sio_acpi_mode);
 		break;
 	case PCH_DEVFN_UART1: /* UART1 */
 		sio_index = SIO_ID_UART1;
-		serialio_d21_ltr(bar0);
+		if (!serialio_uart_is_debug(dev))
+			serialio_d21_ltr(bar0);
 		serialio_d21_mode(sio_index, SIO_PIN_INTD,
 				  config->sio_acpi_mode);
 		break;
@@ -221,8 +237,21 @@ static void serialio_init(struct device *dev)
 		update_bars(sio_index, (u32)bar0->base, (u32)bar1->base);
 }
 
+static void serialio_read_resources(struct device *dev)
+{
+	pci_dev_read_resources(dev);
+
+	/* Set the configured UART base address for the debug port */
+	if (CONFIG(SERIALIO_UART_CONSOLE) && serialio_uart_is_debug(dev)) {
+		struct resource *res = find_resource(dev, PCI_BASE_ADDRESS_0);
+		res->base = CONFIG_CONSOLE_UART_BASE_ADDRESS;
+		res->size = 0x1000;
+		res->flags = IORESOURCE_MEM | IORESOURCE_ASSIGNED | IORESOURCE_FIXED;
+	}
+}
+
 static struct device_operations device_ops = {
-	.read_resources		= pci_dev_read_resources,
+	.read_resources		= serialio_read_resources,
 	.set_resources		= pci_dev_set_resources,
 	.enable_resources	= pci_dev_enable_resources,
 	.init			= serialio_init,
diff --git a/src/southbridge/intel/lynxpoint/uart.c b/src/southbridge/intel/lynxpoint/uart.c
new file mode 100644
index 0000000000..95b286ebfc
--- /dev/null
+++ b/src/southbridge/intel/lynxpoint/uart.c
@@ -0,0 +1,12 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#include <console/uart.h>
+#include <types.h>
+
+uintptr_t uart_platform_base(unsigned int idx)
+{
+	if (idx == CONFIG_UART_FOR_CONSOLE)
+		return CONFIG_CONSOLE_UART_BASE_ADDRESS;
+
+	return 0;
+}
diff --git a/src/southbridge/intel/lynxpoint/uart_init.c b/src/southbridge/intel/lynxpoint/uart_init.c
new file mode 100644
index 0000000000..66b9e01981
--- /dev/null
+++ b/src/southbridge/intel/lynxpoint/uart_init.c
@@ -0,0 +1,54 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#include <arch/io.h>
+#include <arch/mmio.h>
+#include <assert.h>
+#include <console/uart.h>
+#include <device/pci_def.h>
+#include <device/pci_ops.h>
+#include <southbridge/intel/lynxpoint/iobp.h>
+#include <southbridge/intel/lynxpoint/lp_gpio.h>
+#include <southbridge/intel/lynxpoint/pch.h>
+#include <types.h>
+
+static pci_devfn_t get_uart_pci_device(void)
+{
+	switch (CONFIG_UART_FOR_CONSOLE) {
+		case 0:  return PCI_DEV(0, 0x15, 5);
+		case 1:  return PCI_DEV(0, 0x15, 6);
+		default: return dead_code_t(pci_devfn_t);
+	}
+}
+
+/* TODO: Figure out if all steps are actually necessary */
+void uart_bootblock_init(void)
+{
+	const pci_devfn_t dev = get_uart_pci_device();
+
+	/* Program IOBP GPIODF */
+	pch_iobp_update(SIO_IOBP_GPIODF, ~0x131f, 0x131f);
+
+	/* Program IOBP CB000180h[5:0] = 111111b (undefined register) */
+	pch_iobp_update(0xcb000180, ~0x0000003f, 0x0000003f);
+
+	/* Set and enable MMIO BAR */
+	pci_write_config32(dev, PCI_BASE_ADDRESS_0, CONFIG_CONSOLE_UART_BASE_ADDRESS);
+	pci_or_config16(dev, PCI_COMMAND, PCI_COMMAND_MEMORY);
+
+	void *const bar = (void *)(uintptr_t)CONFIG_CONSOLE_UART_BASE_ADDRESS;
+
+	/* Initialize LTR */
+	clrbits32(bar + SIO_REG_PPR_GEN, SIO_REG_PPR_GEN_LTR_MODE_MASK);
+	clrbits32(bar + SIO_REG_PPR_RST, SIO_REG_PPR_RST_ASSERT);
+
+	/* Take UART out of reset */
+	setbits32(bar + SIO_REG_PPR_RST, SIO_REG_PPR_RST_ASSERT);
+
+	/* Set M and N divisor inputs and enable clock */
+	uint32_t ppr_clock = 0;
+	ppr_clock |= SIO_REG_PPR_CLOCK_EN;
+	ppr_clock |= SIO_REG_PPR_CLOCK_UPDATE;
+	ppr_clock |= SIO_REG_PPR_CLOCK_N_DIV << 16;
+	ppr_clock |= SIO_REG_PPR_CLOCK_M_DIV << 1;
+	write32(bar + SIO_REG_PPR_CLOCK, ppr_clock);
+}