drivers/uart/acpi: Add new device driver for UART attached devices

This driver generates an ACPI device object for a UART attached device
with all of the expected device support handlers like different interrupt
sources and power control GPIOs.

Example use:
chip drivers/uart/acpi
    register "name" = ""UDEV""
    register "desc" = ""UART Attached Device""
    register "hid" = "ACPI_DT_NAMESPACE_HID"
    register "compat_string" = ""google,cros-ec-uart""
    register "irq_gpio" = "ACPI_GPIO_IRQ_LEVEL_LOW_WAKE(GPP_C20)"
    register "uart" = "ACPI_UART_RAW_DEVICE(115200, 64)"
    device generic 0 on end
end

Resulting in this ACPI device:

Device (UDEV)
{
    Name (_HID, "PRP0001")
    Name (_UID, Zero)
    Name (_DDN, "UART Attached Device")
    Method (_STA, 0, NotSerialized)
    {
        Return (0x0F)
    }
    Name (_CRS, ResourceTemplate ()
    {
        UartSerialBusV2 (0x0001C200, DataBitsEight, StopBitsOne,
                         0x00, LittleEndian, ParityTypeNone, FlowControlNone,
                         0x0040, 0x0040, "\\_SB.PCI0.UAR2",
                         0x00, ResourceConsumer, , Exclusive)
        GpioInt (Level, ActiveLow, ExclusiveAndWake, PullDefault, 0x0000,
                 "\\_SB.PCI0.GPIO", 0x00, ResourceConsumer)
        {
            0x0114
        }
    })
    Name (_DSD, Package (0x02)
    {
        ToUUID ("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
        Package (0x01)
        {
            Package (0x02)
            {
                "compatible",
                "google,cros-ec-uart"
            }
        }
    })
}

Change-Id: Idfd2d9d2ab6990a82ddd401734c0d9b1b0b8f82d
Signed-off-by: Duncan Laurie <dlaurie@google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/41793
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Furquan Shaikh <furquan@google.com>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>

src/drivers/uart/acpi/Kconfig

@@ -0,0 +1,2 @@
+config DRIVERS_UART_ACPI
+	bool

src/drivers/uart/acpi/Makefile.inc

@@ -0,0 +1 @@
+ramstage-$(CONFIG_DRIVERS_UART_ACPI) += acpi.c

src/drivers/uart/acpi/acpi.c

@@ -0,0 +1,174 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+#include <acpi/acpi_device.h>
+#include <acpi/acpigen.h>
+#include <console/console.h>
+#include <device/path.h>
+#include <string.h>
+#include "chip.h"
+
+static bool uart_acpi_add_gpios_to_crs(struct drivers_uart_acpi_config *config)
+{
+	/*
+	 * Return false if:
+	 * 1. Request to explicitly disable export of GPIOs in CRS, or
+	 * 2. Both reset and enable GPIOs are not provided.
+	 */
+	if (config->disable_gpio_export_in_crs ||
+	    ((config->reset_gpio.pin_count == 0) &&
+	     (config->enable_gpio.pin_count == 0)))
+		return false;
+
+	return true;
+}
+
+static int uart_acpi_write_gpio(struct acpi_gpio *gpio, int *curr_index)
+{
+	int ret = -1;
+
+	if (gpio->pin_count == 0)
+		return ret;
+
+	acpi_device_write_gpio(gpio);
+	ret = *curr_index;
+	(*curr_index)++;
+
+	return ret;
+}
+
+static void uart_acpi_fill_ssdt(const struct device *dev)
+{
+	const char *scope = acpi_device_scope(dev);
+	const char *path = acpi_device_path(dev);
+	struct drivers_uart_acpi_config *config = dev->chip_info;
+	int curr_index = 0;
+	int irq_gpio_index = -1;
+	int reset_gpio_index = -1;
+	int enable_gpio_index = -1;
+
+	if (!dev->enabled || !scope)
+		return;
+
+	if (!config->hid) {
+		printk(BIOS_ERR, "%s: ERROR: HID required\n", dev_path(dev));
+		return;
+	}
+
+	acpigen_write_scope(scope);
+	acpigen_write_device(acpi_device_name(dev));
+
+	acpigen_write_name_string("_HID", config->hid);
+	if (config->cid)
+		acpigen_write_name_string("_CID", config->cid);
+	acpigen_write_name_integer("_UID", config->uid);
+	acpigen_write_name_string("_DDN", config->desc);
+	acpigen_write_STA(acpi_device_status(dev));
+
+	/* Resources */
+	acpigen_write_name("_CRS");
+	acpigen_write_resourcetemplate_header();
+
+	/* Fix up resource pointer to this scope */
+	config->uart.resource = scope;
+	acpi_device_write_uart(&config->uart);
+
+	/* Use either Interrupt() or GpioInt() */
+	if (config->irq_gpio.pin_count)
+		acpi_device_write_gpio(&config->irq_gpio);
+	else
+		acpi_device_write_interrupt(&config->irq);
+
+	/* Add enable/reset GPIOs if needed */
+	if (uart_acpi_add_gpios_to_crs(config)) {
+		reset_gpio_index = uart_acpi_write_gpio(&config->reset_gpio,
+							&curr_index);
+		enable_gpio_index = uart_acpi_write_gpio(&config->enable_gpio,
+							 &curr_index);
+	}
+	acpigen_write_resourcetemplate_footer();
+
+	/* Wake capabilities */
+	if (config->wake) {
+		acpigen_write_name_integer("_S0W", ACPI_DEVICE_SLEEP_D3_COLD);
+		acpigen_write_PRW(config->wake, SLP_TYP_S3);
+	};
+
+	/* Write device properties if needed */
+	if (config->compat_string || irq_gpio_index >= 0 ||
+	    reset_gpio_index >= 0 || enable_gpio_index >= 0) {
+		struct acpi_dp *dsd = acpi_dp_new_table("_DSD");
+		if (config->compat_string)
+			acpi_dp_add_string(dsd, "compatible",
+					   config->compat_string);
+		if (irq_gpio_index >= 0)
+			acpi_dp_add_gpio(dsd, "irq-gpios", path,
+					 irq_gpio_index, 0,
+					 config->irq_gpio.polarity);
+		if (reset_gpio_index >= 0)
+			acpi_dp_add_gpio(dsd, "reset-gpios", path,
+					 reset_gpio_index, 0,
+					 config->reset_gpio.polarity);
+		if (enable_gpio_index >= 0)
+			acpi_dp_add_gpio(dsd, "enable-gpios", path,
+					 enable_gpio_index, 0,
+					 config->enable_gpio.polarity);
+		acpi_dp_write(dsd);
+	}
+
+	/* Power Resource */
+	if (config->has_power_resource) {
+		const struct acpi_power_res_params power_res_params = {
+			&config->reset_gpio,
+			config->reset_delay_ms,
+			config->reset_off_delay_ms,
+			&config->enable_gpio,
+			config->enable_delay_ms,
+			config->enable_off_delay_ms,
+			&config->stop_gpio,
+			config->stop_delay_ms,
+			config->stop_off_delay_ms
+		};
+		acpi_device_add_power_res(&power_res_params);
+	}
+
+	acpigen_pop_len(); /* Device */
+	acpigen_pop_len(); /* Scope */
+
+	printk(BIOS_INFO, "%s: %s at %s\n", path, config->desc, dev_path(dev));
+}
+
+static const char *uart_acpi_name(const struct device *dev)
+{
+	struct drivers_uart_acpi_config *config = dev->chip_info;
+	static char name[5];
+
+	if (config->name)
+		return config->name;
+
+	snprintf(name, sizeof(name), "D%03.3X", dev->path.generic.id);
+	return name;
+}
+
+static struct device_operations uart_acpi_dev_ops = {
+	.read_resources	= noop_read_resources,
+	.set_resources	= noop_set_resources,
+	.acpi_fill_ssdt	= uart_acpi_fill_ssdt,
+	.acpi_name	= uart_acpi_name,
+};
+
+static void uart_acpi_enable(struct device *dev)
+{
+	struct drivers_uart_acpi_config *config = dev->chip_info;
+
+	if (config->desc)
+		dev->name = config->desc;
+	else
+		config->desc = dev->chip_ops->name;
+
+	dev->ops = &uart_acpi_dev_ops;
+}
+
+struct chip_operations drivers_uart_acpi_ops = {
+	CHIP_NAME("ACPI UART Device")
+	.enable_dev = uart_acpi_enable
+};

src/drivers/uart/acpi/chip.h

@@ -0,0 +1,48 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+#ifndef __DRIVERS_UART_ACPI_H__
+#define __DRIVERS_UART_ACPI_H__
+
+#include <acpi/acpi_device.h>
+
+struct drivers_uart_acpi_config {
+	const char *hid;		/* ACPI _HID (required) */
+	const char *cid;		/* ACPI _CID */
+	const char *name;		/* ACPI Device Name */
+	const char *desc;		/* Device Description */
+	unsigned int uid;		/* ACPI _UID */
+	unsigned int wake;		/* Wake GPE */
+	const char *compat_string;	/* Compatible string for _HID=PRP0001 */
+	struct acpi_irq irq;		/* PIRQ */
+	struct acpi_gpio irq_gpio;	/* GPIO to be used instead of PIRQ */
+	struct acpi_uart uart;		/* UART device information */
+
+	/* Disable reset and enable GPIO export in _CRS */
+	bool disable_gpio_export_in_crs;
+
+	/* Does the device have a power resource? */
+	bool has_power_resource;
+
+	/* GPIO used to take device out of reset or to put it into reset. */
+	struct acpi_gpio reset_gpio;
+	/* Delay to be inserted after device is taken out of reset. */
+	unsigned int reset_delay_ms;
+	/* Delay to be inserted after device is put into reset. */
+	unsigned int reset_off_delay_ms;
+
+	/* GPIO used to enable device. */
+	struct acpi_gpio enable_gpio;
+	/* Delay to be inserted after device is enabled. */
+	unsigned int enable_delay_ms;
+	/* Delay to be inserted after device is disabled. */
+	unsigned int enable_off_delay_ms;
+
+	/* GPIO used to stop operation of device. */
+	struct acpi_gpio stop_gpio;
+	/* Delay to be inserted after disabling stop. */
+	unsigned int stop_delay_ms;
+	/* Delay to be inserted after enabling stop. */
+	unsigned int stop_off_delay_ms;
+};
+
+#endif /* __DRIVERS_UART_ACPI_H__ */