[PATCH v5 17/17] serial: 8250: Add 8250_acpi driver

[Sunil V L]

RISC-V has non-PNP generic 16550A compatible UART which needs to be
enumerated as ACPI platform device. Add driver support for such devices
similar to 8250_of.

The driver is enabled when the CONFIG_SERIAL_ACPI_PLATFORM option is
enabled. Enable this option for RISC-V.

Signed-off-by: Sunil V L <sunilvl at ventanamicro.com>
---
 arch/riscv/configs/defconfig        |  1 +
 drivers/tty/serial/8250/8250_acpi.c | 96 +++++++++++++++++++++++++++++
 drivers/tty/serial/8250/Kconfig     |  8 +++
 drivers/tty/serial/8250/Makefile    |  1 +
 4 files changed, 106 insertions(+)
 create mode 100644 drivers/tty/serial/8250/8250_acpi.c

diff --git a/arch/riscv/configs/defconfig b/arch/riscv/configs/defconfig
index 3cae018f9315..bea8241f52eb 100644
--- a/arch/riscv/configs/defconfig
+++ b/arch/riscv/configs/defconfig
@@ -150,6 +150,7 @@ CONFIG_SERIAL_8250=y
 CONFIG_SERIAL_8250_CONSOLE=y
 CONFIG_SERIAL_8250_DW=y
 CONFIG_SERIAL_OF_PLATFORM=y
+CONFIG_SERIAL_ACPI_PLATFORM=y
 CONFIG_SERIAL_SH_SCI=y
 CONFIG_SERIAL_EARLYCON_RISCV_SBI=y
 CONFIG_VIRTIO_CONSOLE=y
diff --git a/drivers/tty/serial/8250/8250_acpi.c b/drivers/tty/serial/8250/8250_acpi.c
new file mode 100644
index 000000000000..3682443bb69c
--- /dev/null
+++ b/drivers/tty/serial/8250/8250_acpi.c
@@ -0,0 +1,96 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Serial Port driver for ACPI platform devices
+ *
+ * This driver is for generic 16550 compatible UART enumerated via ACPI
+ * platform bus instead of PNP bus like PNP0501. This is not a full
+ * driver but mostly provides the ACPI wrapper and uses generic
+ * 8250 framework for rest of the functionality.
+ */
+
+#include <linux/acpi.h>
+#include <linux/serial_reg.h>
+#include <linux/serial_8250.h>
+
+#include "8250.h"
+
+struct acpi_serial_info {
+	int	line;
+};
+
+static int acpi_platform_serial_probe(struct platform_device *pdev)
+{
+	struct acpi_serial_info *data;
+	struct uart_8250_port port8250;
+	struct device *dev = &pdev->dev;
+	struct resource *regs;
+
+	int ret, irq;
+
+	regs = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (!regs) {
+		dev_err(dev, "no registers defined\n");
+		return -EINVAL;
+	}
+
+	irq = platform_get_irq(pdev, 0);
+	if (irq < 0)
+		return irq;
+
+	memset(&port8250, 0, sizeof(port8250));
+
+	spin_lock_init(&port8250.port.lock);
+
+	port8250.port.mapbase           = regs->start;
+	port8250.port.irq               = irq;
+	port8250.port.type              = PORT_16550A;
+	port8250.port.flags             = UPF_SHARE_IRQ | UPF_BOOT_AUTOCONF | UPF_FIXED_PORT |
+					  UPF_IOREMAP | UPF_FIXED_TYPE;
+	port8250.port.dev               = dev;
+	port8250.port.mapsize           = resource_size(regs);
+	port8250.port.iotype            = UPIO_MEM;
+	port8250.port.irqflags          = IRQF_SHARED;
+
+	port8250.port.membase = devm_ioremap(dev, port8250.port.mapbase, port8250.port.mapsize);
+	if (!port8250.port.membase)
+		return -ENOMEM;
+
+	ret = uart_read_and_validate_port_properties(&port8250.port);
+	if (ret)
+		return -EINVAL;
+
+	data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	data->line = serial8250_register_8250_port(&port8250);
+	if (data->line < 0)
+		return data->line;
+
+	platform_set_drvdata(pdev, data);
+	return 0;
+}
+
+static void acpi_platform_serial_remove(struct platform_device *pdev)
+{
+	struct acpi_serial_info *data = platform_get_drvdata(pdev);
+
+	serial8250_unregister_port(data->line);
+}
+
+static const struct acpi_device_id acpi_platform_serial_table[] = {
+	{ "RSCV0003", 0 },
+	{ },
+};
+MODULE_DEVICE_TABLE(acpi, acpi_platform_serial_table);
+
+static struct platform_driver acpi_platform_serial_driver = {
+	.driver = {
+		.name			= "acpi_serial",
+		.acpi_match_table	= ACPI_PTR(acpi_platform_serial_table),
+	},
+	.probe			= acpi_platform_serial_probe,
+	.remove_new		= acpi_platform_serial_remove,
+};
+
+builtin_platform_driver(acpi_platform_serial_driver);
diff --git a/drivers/tty/serial/8250/Kconfig b/drivers/tty/serial/8250/Kconfig
index 47ff50763c04..fbfe4d3501b1 100644
--- a/drivers/tty/serial/8250/Kconfig
+++ b/drivers/tty/serial/8250/Kconfig
@@ -576,3 +576,11 @@ config SERIAL_OF_PLATFORM
 	  are probed through devicetree, including Open Firmware based
 	  PowerPC systems and embedded systems on architectures using the
 	  flattened device tree format.
+
+config SERIAL_ACPI_PLATFORM
+	tristate "ACPI platform bus based probing for 8250 ports"
+	depends on SERIAL_8250 && ACPI
+	default n
+	help
+	  This option is used for generic 8250 compatible serial ports
+	  that are enumerated through ACPI platform bus.
diff --git a/drivers/tty/serial/8250/Makefile b/drivers/tty/serial/8250/Makefile
index ea2e81f58eac..8c0ef357fc4e 100644
--- a/drivers/tty/serial/8250/Makefile
+++ b/drivers/tty/serial/8250/Makefile
@@ -18,6 +18,7 @@ obj-$(CONFIG_SERIAL_8250_CONSOLE)	+= 8250_early.o
 
 obj-$(CONFIG_SERIAL_8250_ACCENT)	+= 8250_accent.o
 obj-$(CONFIG_SERIAL_8250_ACORN)		+= 8250_acorn.o
+obj-$(CONFIG_SERIAL_ACPI_PLATFORM)	+= 8250_acpi.o
 obj-$(CONFIG_SERIAL_8250_ASPEED_VUART)	+= 8250_aspeed_vuart.o
 obj-$(CONFIG_SERIAL_8250_BCM2835AUX)	+= 8250_bcm2835aux.o
 obj-$(CONFIG_SERIAL_8250_BCM7271)	+= 8250_bcm7271.o
-- 
2.40.1