serial: 8250_fsl: Add ACPI support

This adds support for ACPI enumerated FSL 16550 UARTs.
For supporting ACPI, I added a wrapper so that this driver
can be used if firmware has exposed the HID "NXP0018" in
DSDT table.

This will be built as object file if config "SERIAL_8250_FSL"
is enabled which depends on config "SERIAL_8250_CONSOLE".
Signed-off-by: kuldip dwivedi <kuldip.dwivedi@puresoftware.com>
Link: https://lore.kernel.org/r/20200903113402.12371-1-kuldip.dwivedi@puresoftware.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/8250/8250_fsl.c

 // SPDX-License-Identifier: GPL-2.0
-#include <linux/serial_reg.h>
-#include <linux/serial_8250.h>
-
-#include "8250.h"
-
 /*
  * Freescale 16550 UART "driver", Copyright (C) 2011 Paul Gortmaker.
+ * Copyright 2020 NXP
+ * Copyright 2020 Puresoftware Ltd.
  *
  * This isn't a full driver; it just provides an alternate IRQ
- * handler to deal with an errata.  Everything else is just
- * using the bog standard 8250 support.
+ * handler to deal with an errata and provide ACPI wrapper.
+ * Everything else is just using the bog standard 8250 support.
  *
  * We follow code flow of serial8250_default_handle_irq() but add
  * a check for a break and insert a dummy read on the Rx for the
@@ -20,6 +17,16 @@
  * IRQ event to the next one.
  */
 
+#include <linux/acpi.h>
+#include <linux/serial_reg.h>
+#include <linux/serial_8250.h>
+
+#include "8250.h"
+
+struct fsl8250_data {
+	int	line;
+};
+
 int fsl8250_handle_irq(struct uart_port *port)
 {
 	unsigned char lsr, orig_lsr;
@@ -79,3 +86,90 @@ int fsl8250_handle_irq(struct uart_port *port)
 	return 1;
 }
 EXPORT_SYMBOL_GPL(fsl8250_handle_irq);
+
+#ifdef CONFIG_ACPI
+static int fsl8250_acpi_probe(struct platform_device *pdev)
+{
+	struct fsl8250_data *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) {
+		if (irq != -EPROBE_DEFER)
+			dev_err(dev, "cannot get irq\n");
+		return irq;
+	}
+
+	memset(&port8250, 0, sizeof(port8250));
+
+	ret = device_property_read_u32(dev, "clock-frequency",
+					&port8250.port.uartclk);
+	if (ret)
+		return ret;
+
+	spin_lock_init(&port8250.port.lock);
+
+	port8250.port.mapbase           = regs->start;
+	port8250.port.irq               = irq;
+	port8250.port.handle_irq        = fsl8250_handle_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;
+
+	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 int fsl8250_acpi_remove(struct platform_device *pdev)
+{
+	struct fsl8250_data *data = platform_get_drvdata(pdev);
+
+	serial8250_unregister_port(data->line);
+	return 0;
+}
+
+static const struct acpi_device_id fsl_8250_acpi_id[] = {
+	{ "NXP0018", 0 },
+	{ },
+};
+MODULE_DEVICE_TABLE(acpi, fsl_8250_acpi_id);
+
+static struct platform_driver fsl8250_platform_driver = {
+	.driver = {
+		.name			= "fsl-16550-uart",
+		.acpi_match_table	= ACPI_PTR(fsl_8250_acpi_id),
+	},
+	.probe			= fsl8250_acpi_probe,
+	.remove			= fsl8250_acpi_remove,
+};
+
+module_platform_driver(fsl8250_platform_driver);
+#endif