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

[Pranavkumar Sawargaonkar <psawargaonkar@apm.com>]

Hi Ian,

On Fri, Sep 20, 2013 at 7:10 PM, Ian Campbell <ian.campbell@citrix.com> wrote:
> 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?

We will be happy to try that, when will it be merged in xen git repo any idea ?

>
>>
>> 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:
>> + */
>
>
>
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Thanks,
Pranav