SERIAL: AR933X: Add driver for the built-in UART of the SoC

This patch adds the driver for the built-in UART of the
Atheros AR933X SoCs.

Signed-off-by: Gabor Juhos <juhosg@openwrt.org>
Cc: linux-mips@linux-mips.org
Cc: Kathy Giori <kgiori@qca.qualcomm.com>
Cc: "Luis R.  Rodriguez" <rodrigue@qca.qualcomm.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: linux-serial@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/2526/
Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

1 files changed, 688 insertions, 0 deletions

diff --git a/drivers/tty/serial/ar933x_uart.c b/drivers/tty/serial/ar933x_uart.c
new file mode 100644
index 000000000000..e4f60e2b87f3
--- /dev/null
+++ b/drivers/tty/serial/ar933x_uart.c
@@ -0,0 +1,688 @@
+/*
+ *  Atheros AR933X SoC built-in UART driver
+ *
+ *  Copyright (C) 2011 Gabor Juhos <juhosg@openwrt.org>
+ *
+ *  Based on drivers/char/serial.c, by Linus Torvalds, Theodore Ts'o.
+ *
+ *  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.
+ */
+
+#include <linux/module.h>
+#include <linux/ioport.h>
+#include <linux/init.h>
+#include <linux/console.h>
+#include <linux/sysrq.h>
+#include <linux/delay.h>
+#include <linux/platform_device.h>
+#include <linux/tty.h>
+#include <linux/tty_flip.h>
+#include <linux/serial_core.h>
+#include <linux/serial.h>
+#include <linux/slab.h>
+#include <linux/io.h>
+#include <linux/irq.h>
+
+#include <asm/mach-ath79/ar933x_uart.h>
+#include <asm/mach-ath79/ar933x_uart_platform.h>
+
+#define DRIVER_NAME "ar933x-uart"
+
+#define AR933X_DUMMY_STATUS_RD  0x01
+
+static struct uart_driver ar933x_uart_driver;
+
+struct ar933x_uart_port {
+        struct uart_port        port;
+        unsigned int            ier;    /* shadow Interrupt Enable Register */
+};
+
+static inline unsigned int ar933x_uart_read(struct ar933x_uart_port *up,
+                                            int offset)
+{
+        return readl(up->port.membase + offset);
+}
+
+static inline void ar933x_uart_write(struct ar933x_uart_port *up,
+                                     int offset, unsigned int value)
+{
+        writel(value, up->port.membase + offset);
+}
+
+static inline void ar933x_uart_rmw(struct ar933x_uart_port *up,
+                                  unsigned int offset,
+                                  unsigned int mask,
+                                  unsigned int val)
+{
+        unsigned int t;
+
+        t = ar933x_uart_read(up, offset);
+        t &= ~mask;
+        t |= val;
+        ar933x_uart_write(up, offset, t);
+}
+
+static inline void ar933x_uart_rmw_set(struct ar933x_uart_port *up,
+                                       unsigned int offset,
+                                       unsigned int val)
+{
+        ar933x_uart_rmw(up, offset, 0, val);
+}
+
+static inline void ar933x_uart_rmw_clear(struct ar933x_uart_port *up,
+                                         unsigned int offset,
+                                         unsigned int val)
+{
+        ar933x_uart_rmw(up, offset, val, 0);
+}
+
+static inline void ar933x_uart_start_tx_interrupt(struct ar933x_uart_port *up)
+{
+        up->ier |= AR933X_UART_INT_TX_EMPTY;
+        ar933x_uart_write(up, AR933X_UART_INT_EN_REG, up->ier);
+}
+
+static inline void ar933x_uart_stop_tx_interrupt(struct ar933x_uart_port *up)
+{
+        up->ier &= ~AR933X_UART_INT_TX_EMPTY;
+        ar933x_uart_write(up, AR933X_UART_INT_EN_REG, up->ier);
+}
+
+static inline void ar933x_uart_putc(struct ar933x_uart_port *up, int ch)
+{
+        unsigned int rdata;
+
+        rdata = ch & AR933X_UART_DATA_TX_RX_MASK;
+        rdata |= AR933X_UART_DATA_TX_CSR;
+        ar933x_uart_write(up, AR933X_UART_DATA_REG, rdata);
+}
+
+static unsigned int ar933x_uart_tx_empty(struct uart_port *port)
+{
+        struct ar933x_uart_port *up = (struct ar933x_uart_port *) port;
+        unsigned long flags;
+        unsigned int rdata;
+
+        spin_lock_irqsave(&up->port.lock, flags);
+        rdata = ar933x_uart_read(up, AR933X_UART_DATA_REG);
+        spin_unlock_irqrestore(&up->port.lock, flags);
+
+        return (rdata & AR933X_UART_DATA_TX_CSR) ? 0 : TIOCSER_TEMT;
+}
+
+static unsigned int ar933x_uart_get_mctrl(struct uart_port *port)
+{
+        return TIOCM_CAR;
+}
+
+static void ar933x_uart_set_mctrl(struct uart_port *port, unsigned int mctrl)
+{
+}
+
+static void ar933x_uart_start_tx(struct uart_port *port)
+{
+        struct ar933x_uart_port *up = (struct ar933x_uart_port *) port;
+
+        ar933x_uart_start_tx_interrupt(up);
+}
+
+static void ar933x_uart_stop_tx(struct uart_port *port)
+{
+        struct ar933x_uart_port *up = (struct ar933x_uart_port *) port;
+
+        ar933x_uart_stop_tx_interrupt(up);
+}
+
+static void ar933x_uart_stop_rx(struct uart_port *port)
+{
+        struct ar933x_uart_port *up = (struct ar933x_uart_port *) port;
+
+        up->ier &= ~AR933X_UART_INT_RX_VALID;
+        ar933x_uart_write(up, AR933X_UART_INT_EN_REG, up->ier);
+}
+
+static void ar933x_uart_break_ctl(struct uart_port *port, int break_state)
+{
+        struct ar933x_uart_port *up = (struct ar933x_uart_port *) port;
+        unsigned long flags;
+
+        spin_lock_irqsave(&up->port.lock, flags);
+        if (break_state == -1)
+                ar933x_uart_rmw_set(up, AR933X_UART_CS_REG,
+                                    AR933X_UART_CS_TX_BREAK);
+        else
+                ar933x_uart_rmw_clear(up, AR933X_UART_CS_REG,
+                                      AR933X_UART_CS_TX_BREAK);
+        spin_unlock_irqrestore(&up->port.lock, flags);
+}
+
+static void ar933x_uart_enable_ms(struct uart_port *port)
+{
+}
+
+static void ar933x_uart_set_termios(struct uart_port *port,
+                                    struct ktermios *new,
+                                    struct ktermios *old)
+{
+        struct ar933x_uart_port *up = (struct ar933x_uart_port *) port;
+        unsigned int cs;
+        unsigned long flags;
+        unsigned int baud, scale;
+
+        /* Only CS8 is supported */
+        new->c_cflag &= ~CSIZE;
+        new->c_cflag |= CS8;
+
+        /* Only one stop bit is supported */
+        new->c_cflag &= ~CSTOPB;
+
+        cs = 0;
+        if (new->c_cflag & PARENB) {
+                if (!(new->c_cflag & PARODD))
+                        cs |= AR933X_UART_CS_PARITY_EVEN;
+                else
+                        cs |= AR933X_UART_CS_PARITY_ODD;
+        } else {
+                cs |= AR933X_UART_CS_PARITY_NONE;
+        }
+
+        /* Mark/space parity is not supported */
+        new->c_cflag &= ~CMSPAR;
+
+        baud = uart_get_baud_rate(port, new, old, 0, port->uartclk / 16);
+        scale = (port->uartclk / (16 * baud)) - 1;
+
+        /*
+         * Ok, we're now changing the port state. Do it with
+         * interrupts disabled.
+         */
+        spin_lock_irqsave(&up->port.lock, flags);
+
+        /* Update the per-port timeout. */
+        uart_update_timeout(port, new->c_cflag, baud);
+
+        up->port.ignore_status_mask = 0;
+
+        /* ignore all characters if CREAD is not set */
+        if ((new->c_cflag & CREAD) == 0)
+                up->port.ignore_status_mask |= AR933X_DUMMY_STATUS_RD;
+
+        ar933x_uart_write(up, AR933X_UART_CLOCK_REG,
+                          scale << AR933X_UART_CLOCK_SCALE_S | 8192);
+
+        /* setup configuration register */
+        ar933x_uart_rmw(up, AR933X_UART_CS_REG, AR933X_UART_CS_PARITY_M, cs);
+
+        /* enable host interrupt */
+        ar933x_uart_rmw_set(up, AR933X_UART_CS_REG,
+                            AR933X_UART_CS_HOST_INT_EN);
+
+        spin_unlock_irqrestore(&up->port.lock, flags);
+
+        if (tty_termios_baud_rate(new))
+                tty_termios_encode_baud_rate(new, baud, baud);
+}
+
+static void ar933x_uart_rx_chars(struct ar933x_uart_port *up)
+{
+        struct tty_struct *tty;
+        int max_count = 256;
+
+        tty = tty_port_tty_get(&up->port.state->port);
+        do {
+                unsigned int rdata;
+                unsigned char ch;
+
+                rdata = ar933x_uart_read(up, AR933X_UART_DATA_REG);
+                if ((rdata & AR933X_UART_DATA_RX_CSR) == 0)
+                        break;
+
+                /* remove the character from the FIFO */
+                ar933x_uart_write(up, AR933X_UART_DATA_REG,
+                                  AR933X_UART_DATA_RX_CSR);
+
+                if (!tty) {
+                        /* discard the data if no tty available */
+                        continue;
+                }
+
+                up->port.icount.rx++;
+                ch = rdata & AR933X_UART_DATA_TX_RX_MASK;
+
+                if (uart_handle_sysrq_char(&up->port, ch))
+                        continue;
+
+                if ((up->port.ignore_status_mask & AR933X_DUMMY_STATUS_RD) == 0)
+                        tty_insert_flip_char(tty, ch, TTY_NORMAL);
+        } while (max_count-- > 0);
+
+        if (tty) {
+                tty_flip_buffer_push(tty);
+                tty_kref_put(tty);
+        }
+}
+
+static void ar933x_uart_tx_chars(struct ar933x_uart_port *up)
+{
+        struct circ_buf *xmit = &up->port.state->xmit;
+        int count;
+
+        if (uart_tx_stopped(&up->port))
+                return;
+
+        count = up->port.fifosize;
+        do {
+                unsigned int rdata;
+
+                rdata = ar933x_uart_read(up, AR933X_UART_DATA_REG);
+                if ((rdata & AR933X_UART_DATA_TX_CSR) == 0)
+                        break;
+
+                if (up->port.x_char) {
+                        ar933x_uart_putc(up, up->port.x_char);
+                        up->port.icount.tx++;
+                        up->port.x_char = 0;
+                        continue;
+                }
+
+                if (uart_circ_empty(xmit))
+                        break;
+
+                ar933x_uart_putc(up, xmit->buf[xmit->tail]);
+
+                xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
+                up->port.icount.tx++;
+        } while (--count > 0);
+
+        if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
+                uart_write_wakeup(&up->port);
+
+        if (!uart_circ_empty(xmit))
+                ar933x_uart_start_tx_interrupt(up);
+}
+
+static irqreturn_t ar933x_uart_interrupt(int irq, void *dev_id)
+{
+        struct ar933x_uart_port *up = dev_id;
+        unsigned int status;
+
+        status = ar933x_uart_read(up, AR933X_UART_CS_REG);
+        if ((status & AR933X_UART_CS_HOST_INT) == 0)
+                return IRQ_NONE;
+
+        spin_lock(&up->port.lock);
+
+        status = ar933x_uart_read(up, AR933X_UART_INT_REG);
+        status &= ar933x_uart_read(up, AR933X_UART_INT_EN_REG);
+
+        if (status & AR933X_UART_INT_RX_VALID) {
+                ar933x_uart_write(up, AR933X_UART_INT_REG,
+                                  AR933X_UART_INT_RX_VALID);
+                ar933x_uart_rx_chars(up);
+        }
+
+        if (status & AR933X_UART_INT_TX_EMPTY) {
+                ar933x_uart_write(up, AR933X_UART_INT_REG,
+                                  AR933X_UART_INT_TX_EMPTY);
+                ar933x_uart_stop_tx_interrupt(up);
+                ar933x_uart_tx_chars(up);
+        }
+
+        spin_unlock(&up->port.lock);
+
+        return IRQ_HANDLED;
+}
+
+static int ar933x_uart_startup(struct uart_port *port)
+{
+        struct ar933x_uart_port *up = (struct ar933x_uart_port *) port;
+        unsigned long flags;
+        int ret;
+
+        ret = request_irq(up->port.irq, ar933x_uart_interrupt,
+                          up->port.irqflags, dev_name(up->port.dev), up);
+        if (ret)
+                return ret;
+
+        spin_lock_irqsave(&up->port.lock, flags);
+
+        /* Enable HOST interrupts */
+        ar933x_uart_rmw_set(up, AR933X_UART_CS_REG,
+                            AR933X_UART_CS_HOST_INT_EN);
+
+        /* Enable RX interrupts */
+        up->ier = AR933X_UART_INT_RX_VALID;
+        ar933x_uart_write(up, AR933X_UART_INT_EN_REG, up->ier);
+
+        spin_unlock_irqrestore(&up->port.lock, flags);
+
+        return 0;
+}
+
+static void ar933x_uart_shutdown(struct uart_port *port)
+{
+        struct ar933x_uart_port *up = (struct ar933x_uart_port *) port;
+
+        /* Disable all interrupts */
+        up->ier = 0;
+        ar933x_uart_write(up, AR933X_UART_INT_EN_REG, up->ier);
+
+        /* Disable break condition */
+        ar933x_uart_rmw_clear(up, AR933X_UART_CS_REG,
+                              AR933X_UART_CS_TX_BREAK);
+
+        free_irq(up->port.irq, up);
+}
+
+static const char *ar933x_uart_type(struct uart_port *port)
+{
+        return (port->type == PORT_AR933X) ? "AR933X UART" : NULL;
+}
+
+static void ar933x_uart_release_port(struct uart_port *port)
+{
+        /* Nothing to release ... */
+}
+
+static int ar933x_uart_request_port(struct uart_port *port)
+{
+        /* UARTs always present */
+        return 0;
+}
+
+static void ar933x_uart_config_port(struct uart_port *port, int flags)
+{
+        if (flags & UART_CONFIG_TYPE)
+                port->type = PORT_AR933X;
+}
+
+static int ar933x_uart_verify_port(struct uart_port *port,
+                                   struct serial_struct *ser)
+{
+        if (ser->type != PORT_UNKNOWN &&
+            ser->type != PORT_AR933X)
+                return -EINVAL;
+
+        if (ser->irq < 0 || ser->irq >= NR_IRQS)
+                return -EINVAL;
+
+        if (ser->baud_base < 28800)
+                return -EINVAL;
+
+        return 0;
+}
+
+static struct uart_ops ar933x_uart_ops = {
+        .tx_empty       = ar933x_uart_tx_empty,
+        .set_mctrl      = ar933x_uart_set_mctrl,
+        .get_mctrl      = ar933x_uart_get_mctrl,
+        .stop_tx        = ar933x_uart_stop_tx,
+        .start_tx       = ar933x_uart_start_tx,
+        .stop_rx        = ar933x_uart_stop_rx,
+        .enable_ms      = ar933x_uart_enable_ms,
+        .break_ctl      = ar933x_uart_break_ctl,
+        .startup        = ar933x_uart_startup,
+        .shutdown       = ar933x_uart_shutdown,
+        .set_termios    = ar933x_uart_set_termios,
+        .type           = ar933x_uart_type,
+        .release_port   = ar933x_uart_release_port,
+        .request_port   = ar933x_uart_request_port,
+        .config_port    = ar933x_uart_config_port,
+        .verify_port    = ar933x_uart_verify_port,
+};
+
+#ifdef CONFIG_SERIAL_AR933X_CONSOLE
+
+static struct ar933x_uart_port *
+ar933x_console_ports[CONFIG_SERIAL_AR933X_NR_UARTS];
+
+static void ar933x_uart_wait_xmitr(struct ar933x_uart_port *up)
+{
+        unsigned int status;
+        unsigned int timeout = 60000;
+
+        /* Wait up to 60ms for the character(s) to be sent. */
+        do {
+                status = ar933x_uart_read(up, AR933X_UART_DATA_REG);
+                if (--timeout == 0)
+                        break;
+                udelay(1);
+        } while ((status & AR933X_UART_DATA_TX_CSR) == 0);
+}
+
+static void ar933x_uart_console_putchar(struct uart_port *port, int ch)
+{
+        struct ar933x_uart_port *up = (struct ar933x_uart_port *) port;
+
+        ar933x_uart_wait_xmitr(up);
+        ar933x_uart_putc(up, ch);
+}
+
+static void ar933x_uart_console_write(struct console *co, const char *s,
+                                      unsigned int count)
+{
+        struct ar933x_uart_port *up = ar933x_console_ports[co->index];
+        unsigned long flags;
+        unsigned int int_en;
+        int locked = 1;
+
+        local_irq_save(flags);
+
+        if (up->port.sysrq)
+                locked = 0;
+        else if (oops_in_progress)
+                locked = spin_trylock(&up->port.lock);
+        else
+                spin_lock(&up->port.lock);
+
+        /*
+         * First save the IER then disable the interrupts
+         */
+        int_en = ar933x_uart_read(up, AR933X_UART_INT_EN_REG);
+        ar933x_uart_write(up, AR933X_UART_INT_EN_REG, 0);
+
+        uart_console_write(&up->port, s, count, ar933x_uart_console_putchar);
+
+        /*
+         * Finally, wait for transmitter to become empty
+         * and restore the IER
+         */
+        ar933x_uart_wait_xmitr(up);
+        ar933x_uart_write(up, AR933X_UART_INT_EN_REG, int_en);
+
+        ar933x_uart_write(up, AR933X_UART_INT_REG, AR933X_UART_INT_ALLINTS);
+
+        if (locked)
+                spin_unlock(&up->port.lock);
+
+        local_irq_restore(flags);
+}
+
+static int ar933x_uart_console_setup(struct console *co, char *options)
+{
+        struct ar933x_uart_port *up;
+        int baud = 115200;
+        int bits = 8;
+        int parity = 'n';
+        int flow = 'n';
+
+        if (co->index < 0 || co->index >= CONFIG_SERIAL_AR933X_NR_UARTS)
+                return -EINVAL;
+
+        up = ar933x_console_ports[co->index];
+        if (!up)
+                return -ENODEV;
+
+        if (options)
+                uart_parse_options(options, &baud, &parity, &bits, &flow);
+
+        return uart_set_options(&up->port, co, baud, parity, bits, flow);
+}
+
+static struct console ar933x_uart_console = {
+        .name           = "ttyATH",
+        .write          = ar933x_uart_console_write,
+        .device         = uart_console_device,
+        .setup          = ar933x_uart_console_setup,
+        .flags          = CON_PRINTBUFFER,
+        .index          = -1,
+        .data           = &ar933x_uart_driver,
+};
+
+static void ar933x_uart_add_console_port(struct ar933x_uart_port *up)
+{
+        ar933x_console_ports[up->port.line] = up;
+}
+
+#define AR933X_SERIAL_CONSOLE   (&ar933x_uart_console)
+
+#else
+
+static inline void ar933x_uart_add_console_port(struct ar933x_uart_port *up) {}
+
+#define AR933X_SERIAL_CONSOLE   NULL
+
+#endif /* CONFIG_SERIAL_AR933X_CONSOLE */
+
+static struct uart_driver ar933x_uart_driver = {
+        .owner          = THIS_MODULE,
+        .driver_name    = DRIVER_NAME,
+        .dev_name       = "ttyATH",
+        .nr             = CONFIG_SERIAL_AR933X_NR_UARTS,
+        .cons           = AR933X_SERIAL_CONSOLE,
+};
+
+static int __devinit ar933x_uart_probe(struct platform_device *pdev)
+{
+        struct ar933x_uart_platform_data *pdata;
+        struct ar933x_uart_port *up;
+        struct uart_port *port;
+        struct resource *mem_res;
+        struct resource *irq_res;
+        int id;
+        int ret;
+
+        pdata = pdev->dev.platform_data;
+        if (!pdata)
+                return -EINVAL;
+
+        id = pdev->id;
+        if (id == -1)
+                id = 0;
+
+        if (id > CONFIG_SERIAL_AR933X_NR_UARTS)
+                return -EINVAL;
+
+        mem_res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+        if (!mem_res) {
+                dev_err(&pdev->dev, "no MEM resource\n");
+                return -EINVAL;
+        }
+
+        irq_res = platform_get_resource(pdev, IORESOURCE_IRQ, 0);
+        if (!irq_res) {
+                dev_err(&pdev->dev, "no IRQ resource\n");
+                return -EINVAL;
+        }
+
+        up = kzalloc(sizeof(struct ar933x_uart_port), GFP_KERNEL);
+        if (!up)
+                return -ENOMEM;
+
+        port = &up->port;
+        port->mapbase = mem_res->start;
+
+        port->membase = ioremap(mem_res->start, AR933X_UART_REGS_SIZE);
+        if (!port->membase) {
+                ret = -ENOMEM;
+                goto err_free_up;
+        }
+
+        port->line = id;
+        port->irq = irq_res->start;
+        port->dev = &pdev->dev;
+        port->type = PORT_AR933X;
+        port->iotype = UPIO_MEM32;
+        port->uartclk = pdata->uartclk;
+
+        port->regshift = 2;
+        port->fifosize = AR933X_UART_FIFO_SIZE;
+        port->ops = &ar933x_uart_ops;
+
+        ar933x_uart_add_console_port(up);
+
+        ret = uart_add_one_port(&ar933x_uart_driver, &up->port);
+        if (ret)
+                goto err_unmap;
+
+        platform_set_drvdata(pdev, up);
+        return 0;
+
+err_unmap:
+        iounmap(up->port.membase);
+err_free_up:
+        kfree(up);
+        return ret;
+}
+
+static int __devexit ar933x_uart_remove(struct platform_device *pdev)
+{
+        struct ar933x_uart_port *up;
+
+        up = platform_get_drvdata(pdev);
+        platform_set_drvdata(pdev, NULL);
+
+        if (up) {
+                uart_remove_one_port(&ar933x_uart_driver, &up->port);
+                iounmap(up->port.membase);
+                kfree(up);
+        }
+
+        return 0;
+}
+
+static struct platform_driver ar933x_uart_platform_driver = {
+        .probe          = ar933x_uart_probe,
+        .remove         = __devexit_p(ar933x_uart_remove),
+        .driver         = {
+                .name           = DRIVER_NAME,
+                .owner          = THIS_MODULE,
+        },
+};
+
+static int __init ar933x_uart_init(void)
+{
+        int ret;
+
+        ar933x_uart_driver.nr = CONFIG_SERIAL_AR933X_NR_UARTS;
+        ret = uart_register_driver(&ar933x_uart_driver);
+        if (ret)
+                goto err_out;
+
+        ret = platform_driver_register(&ar933x_uart_platform_driver);
+        if (ret)
+                goto err_unregister_uart_driver;
+
+        return 0;
+
+err_unregister_uart_driver:
+        uart_unregister_driver(&ar933x_uart_driver);
+err_out:
+        return ret;
+}
+
+static void __exit ar933x_uart_exit(void)
+{
+        platform_driver_unregister(&ar933x_uart_platform_driver);
+        uart_unregister_driver(&ar933x_uart_driver);
+}
+
+module_init(ar933x_uart_init);
+module_exit(ar933x_uart_exit);
+
+MODULE_DESCRIPTION("Atheros AR933X UART driver");
+MODULE_AUTHOR("Gabor Juhos <juhosg@openwrt.org>");
+MODULE_LICENSE("GPL v2");
+MODULE_ALIAS("platform:" DRIVER_NAME);