Re: [PATCH 3/4] xen: drivers: char: Add Device Tree Based NS16550 UART driver.

[Ian Campbell <ian.campbell@citrix.com>]

On Fri, 2013-09-20 at 15:22 +0530, Pranavkumar Sawargaonkar wrote:
> This patch adds a device tree based driver for ns16550 UART.

I posted patches last week (or the week before) to support the
cubieboard2 and that series included a patch to enable the existing
ns16550 driver to be used on DT as well. I think that is better than
duplicating the majority of the driver just differ in a few probe
routines.

Does that approach work for you?

> 
> Signed-off-by: Anup Patel <anup.patel@linaro.org>
> Signed-off-by: Pranavkumar Sawargaonkar <pranavkumar@linaro.org>
> ---
>  xen/drivers/char/Makefile     |   1 +
>  xen/drivers/char/ns16550-dt.c | 302 ++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 303 insertions(+)
>  create mode 100644 xen/drivers/char/ns16550-dt.c
> 
> diff --git a/xen/drivers/char/Makefile b/xen/drivers/char/Makefile
> index 911b788..7c22a1b 100644
> --- a/xen/drivers/char/Makefile
> +++ b/xen/drivers/char/Makefile
> @@ -5,4 +5,5 @@ obj-$(HAS_EXYNOS4210) += exynos4210-uart.o
>  obj-$(HAS_OMAP) += omap-uart.o
>  obj-$(HAS_EHCI) += ehci-dbgp.o
>  obj-$(CONFIG_ARM) += dt-uart.o
> +obj-$(HAS_NS16550_DT) += ns16550-dt.o
>  obj-y += serial.o
> diff --git a/xen/drivers/char/ns16550-dt.c b/xen/drivers/char/ns16550-dt.c
> new file mode 100644
> index 0000000..74d2b57
> --- /dev/null
> +++ b/xen/drivers/char/ns16550-dt.c
> @@ -0,0 +1,302 @@
> +/*
> + * xen/drivers/char/ns16550.c
> + *
> + * Driver for ns16550 UART based on DT bindigs.
> + *
> + * Pranavkumar Sawargaonkar <psawargaonkar@apm.com>
> + * Anup Patel <apatel@apm.com>
> + * Copyright (c) 2013 Applied Micro.
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation; either version 2 of the License, or
> + * (at your option) any later version.
> + *
> + * 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 <xen/config.h>
> +#include <xen/console.h>
> +#include <xen/serial.h>
> +#include <xen/init.h>
> +#include <xen/irq.h>
> +#include <asm/early_printk.h>
> +#include <xen/device_tree.h>
> +#include <xen/errno.h>
> +#include <asm/device.h>
> +#include <xen/mm.h>
> +#include <xen/vmap.h>
> +#include <xen/8250-uart.h>
> +
> +static struct ns16550 {
> +    unsigned int baud, clock_hz, data_bits, parity, stop_bits;
> +    unsigned int fifo_size;
> +    unsigned int reg_align; /* Regs alignement */
> +    struct dt_irq irq;
> +    void __iomem *regs;
> +    /* UART with IRQ line: interrupt-driven I/O. */
> +    struct irqaction irqaction;
> +    struct vuart_info vuart;
> +} ns16550_com = {0};
> +
> +
> +static char ns16550_read(struct ns16550 *uart, int reg)
> +{
> +        return ioreadl((uart)->regs + (reg * (uart->reg_align)));
> +}
> +
> +static void ns16550_write(struct ns16550 *uart, int reg, char c)
> +{
> +        iowritel((uart)->regs + (reg * (uart->reg_align)), c);
> +}
> +
> +static void ns16550_interrupt(int irq, void *data, struct cpu_user_regs *regs)
> +{
> +    struct serial_port *port = data;
> +    struct ns16550 *uart = port->uart;
> +
> +    while ( !(ns16550_read(uart, UART_IIR) & UART_IIR_NOINT) )
> +    {
> +        char lsr = ns16550_read(uart, UART_LSR);
> +        if ( lsr & UART_LSR_THRE )
> +            serial_tx_interrupt(port, regs);
> +        if ( lsr & UART_LSR_DR )
> +            serial_rx_interrupt(port, regs);
> +    }
> +}
> +
> +static void ns16550_setup_preirq(struct ns16550 *uart)
> +{
> +    unsigned char lcr;
> +    unsigned int  divisor;
> +
> +    lcr = (uart->data_bits - 5) | ((uart->stop_bits - 1) << 2) | uart->parity;
> +
> +    /* No interrupts. */
> +    ns16550_write(uart, UART_IER, 0);
> +
> +    /* Line control and baud-rate generator. */
> +    ns16550_write(uart, UART_LCR, lcr | UART_LCR_DLAB);
> +    if ( uart->baud != BAUD_AUTO )
> +    {
> +        /* Baud rate specified: program it into the divisor latch. */
> +        divisor = uart->clock_hz / (uart->baud << 4);
> +        ns16550_write(uart, UART_DLL, (char)divisor);
> +        ns16550_write(uart, UART_DLM, (char)(divisor >> 8));
> +    }
> +    else
> +    {
> +        /* Baud rate already set: read it out from the divisor latch. */
> +        divisor  = ns16550_read(uart, UART_DLL);
> +        divisor |= ns16550_read(uart, UART_DLM) << 8;
> +        uart->baud = uart->clock_hz / (divisor << 4);
> +    }
> +    ns16550_write(uart, UART_LCR, lcr);
> +
> +    /* No flow ctrl: DTR and RTS are both wedged high to keep remote happy. */
> +    ns16550_write(uart, UART_MCR, UART_MCR_DTR | UART_MCR_RTS);
> +
> +    /* Enable and clear the FIFOs. Set a large trigger threshold. */
> +    ns16550_write(uart, UART_FCR,
> +                 UART_FCR_ENABLE | UART_FCR_CLRX | UART_FCR_CLTX | UART_FCR_TRG14);
> +}
> +
> +static void __init ns16550_init_preirq(struct serial_port *port)
> +{
> +    struct ns16550 *uart = port->uart;
> +
> +    ns16550_setup_preirq(uart);
> +
> +    /* Check this really is a 16550+. Otherwise we have no FIFOs. */
> +    if ( ((ns16550_read(uart, UART_IIR) & 0xc0) == 0xc0) &&
> +         ((ns16550_read(uart, UART_FCR) & UART_FCR_TRG14) == UART_FCR_TRG14) )
> +        uart->fifo_size = 16;
> +}
> +
> +static void ns16550_setup_postirq(struct ns16550 *uart)
> +{
> +    if ( uart->irq.irq > 0 )
> +    {
> +        /* Master interrupt enable; also keep DTR/RTS asserted. */
> +        ns16550_write(uart,
> +                     UART_MCR, UART_MCR_OUT2 | UART_MCR_DTR | UART_MCR_RTS);
> +
> +        /* Enable receive and transmit interrupts. */
> +        ns16550_write(uart, UART_IER, UART_IER_ERDAI | UART_IER_ETHREI);
> +    }
> +}
> +
> +static void __init ns16550_init_postirq(struct serial_port *port)
> +{
> +    struct ns16550 *uart = port->uart;
> +    int rc, bits;
> +
> +    if ( uart->irq.irq < 0 )
> +        return;
> +
> +    /* Calculate time to fill RX FIFO and/or empty TX FIFO for polling. */
> +    bits = uart->data_bits + uart->stop_bits + !!uart->parity;
> +
> +    if ( uart->irq.irq > 0 )
> +    {
> +        uart->irqaction.handler = ns16550_interrupt;
> +        uart->irqaction.name    = "ns16550";
> +        uart->irqaction.dev_id  = port;
> +        if ( (rc = setup_dt_irq(&uart->irq, &uart->irqaction)) != 0 )
> +            printk("ERROR: Failed to allocate ns16550 IRQ %d\n", uart->irq.irq);
> +    }
> +
> +    ns16550_setup_postirq(uart);
> +}
> +
> +static int ns16550_tx_ready(struct serial_port *port)
> +{
> +    struct ns16550 *uart = port->uart;
> +
> +    return ns16550_read(uart, UART_LSR) & UART_LSR_THRE ? uart->fifo_size : 0;
> +}
> +
> +static void ns16550_putc(struct serial_port *port, char c)
> +{
> +    struct ns16550 *uart = port->uart;
> +
> +    ns16550_write(uart, UART_THR, c);
> +}
> +
> +static int ns16550_getc(struct serial_port *port, char *pc)
> +{
> +    struct ns16550 *uart = port->uart;
> +
> +   if ( !(ns16550_read(uart, UART_LSR) & UART_LSR_DR) )
> +        return 0;
> +
> +    *pc = ns16550_read(uart, UART_RBR);
> +    return 1;
> +}
> +
> +static void ns16550_suspend(struct serial_port *port)
> +{
> +    BUG(); // XXX
> +}
> +
> +static void ns16550_resume(struct serial_port *port)
> +{
> +    BUG(); // XXX
> +}
> +
> +static int __init ns16550_irq(struct serial_port *port)
> +{
> +    struct ns16550 *uart = port->uart;
> +    return ((uart->irq.irq > 0) ? uart->irq.irq : -1);
> +}
> +
> +static const struct dt_irq __init *ns16550_dt_irq(struct serial_port *port)
> +{
> +    struct ns16550 *uart = port->uart;
> +
> +    return &uart->irq;
> +}
> +
> +static const struct vuart_info *ns16550_vuart(struct serial_port *port)
> +{
> +    struct ns16550 *uart = port->uart;
> +
> +    return &uart->vuart;
> +}
> +
> +static struct uart_driver __read_mostly ns16550_driver = {
> +    .init_preirq  = ns16550_init_preirq,
> +    .init_postirq = ns16550_init_postirq,
> +    .endboot      = NULL,
> +    .suspend      = ns16550_suspend,
> +    .resume       = ns16550_resume,
> +    .tx_ready     = ns16550_tx_ready,
> +    .putc         = ns16550_putc,
> +    .getc         = ns16550_getc,
> +    .irq          = ns16550_irq,
> +    .dt_irq_get   = ns16550_dt_irq,
> +    .vuart_info   = ns16550_vuart,
> +};
> +
> +/* TODO: Parse UART config from the command line */
> +static int __init ns16550_uart_init(struct dt_device_node *dev,
> +                                  const void *data)
> +{
> +    const char *config = data;
> +    struct ns16550 *uart;
> +    int res;
> +    u64 addr, size;
> +
> +    if ( strcmp(config, "") )
> +    {
> +        early_printk("WARNING: UART configuration is not supported\n");
> +    }
> +
> +    uart = &ns16550_com;
> +
> +    uart->clock_hz  = 50000000;
> +    uart->baud      = 115200;
> +    uart->data_bits = 8;
> +    uart->parity    = UART_PARITY_NONE; /* FIXME */
> +    uart->stop_bits = 1;
> +    uart->reg_align = 4;
> +
> +    res = dt_device_get_address(dev, 0, &addr, &size);
> +    if ( res )
> +    {
> +        early_printk("ns16550: Unable to retrieve the base"
> +                     " address of the UART\n");
> +        return res;
> +    }
> +
> +    uart->regs = ioremap_attr(addr, size, PAGE_HYPERVISOR_NOCACHE);
> +    if ( !uart->regs )
> +    {
> +        early_printk("ns16550: Unable to map the UART memory\n");
> +
> +        return -ENOMEM;
> +    }
> +
> +    res = dt_device_get_irq(dev, 0, &uart->irq);
> +    if ( res )
> +    {
> +        early_printk("ns16550: Unable to retrieve the IRQ\n");
> +        return res;
> +    }
> +
> +    uart->vuart.base_addr = addr;
> +    uart->vuart.size = size;
> +    uart->vuart.data_off = (UART_THR * uart->reg_align) ;
> +    uart->vuart.status_off = (UART_LSR * uart->reg_align);
> +    uart->vuart.status = UART_LSR_THRE;
> +
> +    /* Register with generic serial driver. */
> +    serial_register_uart(SERHND_DTUART, &ns16550_driver, uart);
> +
> +    dt_device_set_used_by(dev, DOMID_XEN);
> +
> +    return 0;
> +}
> +
> +static const char const *ns16550_dt_compat[] __initdata =
> +{
> +    "ns16550",
> +    NULL
> +};
> +
> +DT_DEVICE_START(ns16550, "NS16550 UART", DEVICE_SERIAL)
> +        .compatible = ns16550_dt_compat,
> +        .init = ns16550_uart_init,
> +DT_DEVICE_END
> +
> +/*
> + * Local variables:
> + * mode: C
> + * c-file-style: "BSD"
> + * c-basic-offset: 4
> + * indent-tabs-mode: nil
> + * End:
> + */