i.MX: Add 'lpuart' serial driver

Add 'lpuart' serial driver, based on analogous driver from U-Boot

Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

drivers/serial/Kconfig

@@ -137,4 +137,9 @@ config DRIVER_SERIAL_DIGIC
 	bool "Canon DIGIC serial driver"
 	depends on ARCH_DIGIC
 
+config DRIVER_SERIAL_LPUART
+	depends on ARCH_VF610
+	default y
+	bool "LPUART serial driver"
+
 endmenu

drivers/serial/Makefile

@@ -20,3 +20,4 @@ obj-$(CONFIG_DRIVER_SERIAL_AUART)		+= serial_auart.o
 obj-$(CONFIG_DRIVER_SERIAL_CADENCE)		+= serial_cadence.o
 obj-$(CONFIG_DRIVER_SERIAL_EFI_STDIO)		+= efi-stdio.o
 obj-$(CONFIG_DRIVER_SERIAL_DIGIC)		+= serial_digic.o
+obj-$(CONFIG_DRIVER_SERIAL_LPUART)		+= serial_lpuart.o

drivers/serial/serial_lpuart.c

@@ -0,0 +1,217 @@
+/*
+ * Copyright (c) 2016 Zodiac Inflight Innovation
+ * Author: Andrey Smirnov <andrew.smirnov@gmail.com>
+ *
+ * Based on analogous driver from U-Boot
+ *
+ * See file CREDITS for list of people who contributed to this
+ * project.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2
+ * as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ */
+
+#include <common.h>
+#include <driver.h>
+#include <init.h>
+#include <malloc.h>
+#include <notifier.h>
+#include <io.h>
+#include <of.h>
+#include <linux/err.h>
+#include <linux/clk.h>
+#include <serial/lpuart.h>
+
+struct lpuart {
+	struct console_device cdev;
+	int baudrate;
+	int dte_mode;
+	struct notifier_block notify;
+	struct resource *io;
+	void __iomem *base;
+	struct clk *clk;
+};
+
+static struct lpuart *cdev_to_lpuart(struct console_device *cdev)
+{
+	return container_of(cdev, struct lpuart, cdev);
+}
+
+static struct lpuart *nb_to_lpuart(struct notifier_block *nb)
+{
+	return container_of(nb, struct lpuart, notify);
+}
+
+static void lpuart_enable(struct lpuart *lpuart, bool on)
+{
+	u8 ctrl;
+
+	ctrl = readb(lpuart->base + UARTCR2);
+	if (on)
+		ctrl |= UARTCR2_TE | UARTCR2_RE;
+	else
+		ctrl &= ~(UARTCR2_TE | UARTCR2_RE);
+	writeb(ctrl, lpuart->base + UARTCR2);
+}
+
+static int lpuart_serial_setbaudrate(struct console_device *cdev,
+				     int baudrate)
+{
+	struct lpuart *lpuart = cdev_to_lpuart(cdev);
+
+	lpuart_enable(lpuart, false);
+
+	lpuart_setbrg(lpuart->base,
+		      clk_get_rate(lpuart->clk),
+		      baudrate);
+
+	lpuart_enable(lpuart, true);
+
+	lpuart->baudrate = baudrate;
+
+	return 0;
+}
+
+static int lpuart_serial_getc(struct console_device *cdev)
+{
+	bool ready;
+	struct lpuart *lpuart = cdev_to_lpuart(cdev);
+
+	do {
+		const u8 sr1 = readb(lpuart->base + UARTSR1);
+		ready = !!(sr1 & (UARTSR1_OR | UARTSR1_RDRF));
+	} while (!ready);
+
+	return readb(lpuart->base + UARTDR);
+}
+
+static void lpuart_serial_putc(struct console_device *cdev, char c)
+{
+	lpuart_putc(cdev_to_lpuart(cdev)->base, c);
+}
+
+/* Test whether a character is in the RX buffer */
+static int lpuart_serial_tstc(struct console_device *cdev)
+{
+	return !!readb(cdev_to_lpuart(cdev)->base + UARTRCFIFO);
+}
+
+static void lpuart_serial_flush(struct console_device *cdev)
+{
+	bool tx_empty;
+	struct lpuart *lpuart = cdev_to_lpuart(cdev);
+
+	do {
+		const u8 sr1 = readb(lpuart->base + UARTSR1);
+		tx_empty = !!(sr1 & UARTSR1_TDRE);
+	} while (!tx_empty);
+}
+
+static int lpuart_clocksource_clock_change(struct notifier_block *nb,
+					   unsigned long event, void *data)
+{
+	struct lpuart *lpuart = nb_to_lpuart(nb);
+
+	return lpuart_serial_setbaudrate(&lpuart->cdev, lpuart->baudrate);
+}
+
+static int lpuart_serial_probe(struct device_d *dev)
+{
+	int ret;
+	struct console_device *cdev;
+	struct lpuart *lpuart;
+	const char *devname;
+
+	lpuart    = xzalloc(sizeof(*lpuart));
+	cdev      = &lpuart->cdev;
+	dev->priv = lpuart;
+
+	lpuart->io = dev_request_mem_resource(dev, 0);
+	if (IS_ERR(lpuart->io)) {
+		ret = PTR_ERR(lpuart->io);
+		goto err_free;
+	}
+	lpuart->base = IOMEM(lpuart->io->start);
+
+	lpuart->clk = clk_get(dev, NULL);
+	if (IS_ERR(lpuart->clk)) {
+		ret = PTR_ERR(lpuart->clk);
+		dev_err(dev, "Failed to get UART clock %d\n", ret);
+		goto io_release;
+	}
+
+	ret = clk_enable(lpuart->clk);
+	if (ret) {
+		dev_err(dev, "Failed to enable UART clock %d\n", ret);
+		goto io_release;
+	}
+
+	cdev->dev    = dev;
+	cdev->tstc   = lpuart_serial_tstc;
+	cdev->putc   = lpuart_serial_putc;
+	cdev->getc   = lpuart_serial_getc;
+	cdev->flush  = lpuart_serial_flush;
+	cdev->setbrg = lpuart_serial_setbaudrate;
+
+	if (dev->device_node) {
+		devname = of_alias_get(dev->device_node);
+		if (devname) {
+			cdev->devname = xstrdup(devname);
+			cdev->devid   = DEVICE_ID_SINGLE;
+		}
+	}
+
+	cdev->linux_console_name = "ttyLP";
+
+	lpuart_setup_with_fifo(lpuart->base,
+			       clk_get_rate(lpuart->clk),
+			       15);
+
+	ret = console_register(cdev);
+	if (!ret) {
+		lpuart->notify.notifier_call = lpuart_clocksource_clock_change;
+		clock_register_client(&lpuart->notify);
+
+		return 0;
+	}
+
+	clk_put(lpuart->clk);
+io_release:
+	release_region(lpuart->io);
+err_free:
+	free(lpuart);
+
+	return ret;
+}
+
+static void lpuart_serial_remove(struct device_d *dev)
+{
+	struct lpuart *lpuart = dev->priv;
+
+	lpuart_serial_flush(&lpuart->cdev);
+	console_unregister(&lpuart->cdev);
+	release_region(lpuart->io);
+	clk_put(lpuart->clk);
+
+	free(lpuart);
+}
+
+static struct of_device_id lpuart_serial_dt_ids[] = {
+	{ .compatible = "fsl,vf610-lpuart" },
+	{}
+};
+
+static struct driver_d lpuart_serial_driver = {
+	.name   = "lpuart-serial",
+	.probe  = lpuart_serial_probe,
+	.remove = lpuart_serial_remove,
+	.of_compatible = DRV_OF_COMPAT(lpuart_serial_dt_ids),
+};
+console_platform_driver(lpuart_serial_driver);