Re: [Qemu-devel] [PATCH v1 17/21] SiFive RISC-V UART Device

[Antony Pavlov <antonynpavlov@gmail.com>]

On Wed,  3 Jan 2018 13:44:21 +1300
Michael Clark <mjc@sifive.com> wrote:

> QEMU model of the UART on the SiFive E300 and U500 series SOCs.
> BBL supports the SiFive UART for early console access via the SBI
> (Supervisor Binary Interface) and the linux kernel SBI console.
> 
> The SiFive UART implements the pre qom legacy interface consistent
> with the 16550a UART in 'hw/char/serial.c'.
> 
> Signed-off-by: Michael Clark <mjc@sifive.com>
> ---
>  hw/riscv/sifive_uart.c         | 182 +++++++++++++++++++++++++++++++++++++++++
>  include/hw/riscv/sifive_uart.h |  76 +++++++++++++++++
>  2 files changed, 258 insertions(+)
>  create mode 100644 hw/riscv/sifive_uart.c
>  create mode 100644 include/hw/riscv/sifive_uart.h
> 
> diff --git a/hw/riscv/sifive_uart.c b/hw/riscv/sifive_uart.c
> new file mode 100644
> index 0000000..0e73df6
> --- /dev/null
> +++ b/hw/riscv/sifive_uart.c
> @@ -0,0 +1,182 @@
> +/*
> + * QEMU model of the UART on the SiFive E300 and U500 series SOCs.
> + *
> + * Copyright (c) 2016 Stefan O'Rear
> + *
> + * Permission is hereby granted, free of charge, to any person obtaining a copy
> + * of this software and associated documentation files (the "Software"), to deal
> + * in the Software without restriction, including without limitation the rights
> + * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
> + * copies of the Software, and to permit persons to whom the Software is
> + * furnished to do so, subject to the following conditions:
> + *
> + * The above copyright notice and this permission notice shall be included in
> + * all copies or substantial portions of the Software.
> + *
> + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
> + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
> + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
> + * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
> + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
> + * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
> + * THE SOFTWARE.
> + */
> +
> +#include "qemu/osdep.h"
> +#include "qapi/error.h"
> +#include "hw/sysbus.h"
> +#include "chardev/char.h"
> +#include "chardev/char-fe.h"
> +#include "target/riscv/cpu.h"
> +#include "hw/riscv/sifive_uart.h"
> +
> +/*
> + * Not yet implemented:
> + *
> + * Transmit FIFO using "qemu/fifo8.h"
> + * SIFIVE_UART_IE_TXWM interrupts
> + * SIFIVE_UART_IE_RXWM interrupts must honor fifo watermark
> + * Rx FIFO watermark interrupt trigger threshold
> + * Tx FIFO watermark interrupt trigger threshold.
> + */
> +
> +static void update_irq(SiFiveUARTState *s)
> +{
> +    int cond = 0;
> +    if ((s->ie & SIFIVE_UART_IE_RXWM) && s->rx_fifo_len) {
> +        cond = 1;
> +    }
> +    if (cond) {
> +        qemu_irq_raise(s->irq);
> +    } else {
> +        qemu_irq_lower(s->irq);
> +    }
> +}
> +
> +static uint64_t
> +uart_read(void *opaque, hwaddr addr, unsigned int size)
> +{
> +    SiFiveUARTState *s = opaque;
> +    unsigned char r;
> +    switch (addr) {
> +    case SIFIVE_UART_RXFIFO:
> +        if (s->rx_fifo_len) {
> +            r = s->rx_fifo[0];
> +            memmove(s->rx_fifo, s->rx_fifo + 1, s->rx_fifo_len - 1);
> +            s->rx_fifo_len--;

qemu already has code for FIFO implementation.

Can we use Fifo8 as hw/char/serial.c does?

Please see my 'hw/sifive_uart: use generic Fifo8' patch:

  https://github.com/riscv/riscv-qemu/pull/60/commits/6d68a4bc9a617b72ec563f72e58e2467998d5c4b


> +            qemu_chr_fe_accept_input(&s->chr);
> +            update_irq(s);
> +            return r;
> +        }
> +        return 0x80000000;
> +
> +    case SIFIVE_UART_TXFIFO:
> +        return 0; /* Should check tx fifo */
> +    case SIFIVE_UART_IE:
> +        return s->ie;
> +    case SIFIVE_UART_IP:
> +        return s->rx_fifo_len ? SIFIVE_UART_IP_RXWM : 0;
> +    case SIFIVE_UART_TXCTRL:
> +        return s->txctrl;
> +    case SIFIVE_UART_RXCTRL:
> +        return s->rxctrl;
> +    case SIFIVE_UART_DIV:
> +        return s->div;
> +    }
> +
> +    hw_error("%s: bad read: addr=0x%x\n",
> +        __func__, (int)addr);
> +    return 0;
> +}
> +
> +static void
> +uart_write(void *opaque, hwaddr addr,
> +           uint64_t val64, unsigned int size)
> +{
> +    SiFiveUARTState *s = opaque;
> +    uint32_t value = val64;
> +    unsigned char ch = value;
> +
> +    switch (addr) {
> +    case SIFIVE_UART_TXFIFO:
> +        qemu_chr_fe_write(&s->chr, &ch, 1);
> +        return;
> +    case SIFIVE_UART_IE:
> +        s->ie = val64;
> +        update_irq(s);
> +        return;
> +    case SIFIVE_UART_TXCTRL:
> +        s->txctrl = val64;
> +        return;
> +    case SIFIVE_UART_RXCTRL:
> +        s->rxctrl = val64;
> +        return;
> +    case SIFIVE_UART_DIV:
> +        s->div = val64;
> +        return;
> +    }
> +    hw_error("%s: bad write: addr=0x%x v=0x%x\n",
> +        __func__, (int)addr, (int)value);
> +}
> +
> +static const MemoryRegionOps uart_ops = {
> +    .read = uart_read,
> +    .write = uart_write,
> +    .endianness = DEVICE_NATIVE_ENDIAN,
> +    .valid = {
> +        .min_access_size = 4,
> +        .max_access_size = 4
> +    }
> +};
> +
> +static void uart_rx(void *opaque, const uint8_t *buf, int size)
> +{
> +    SiFiveUARTState *s = opaque;
> +
> +    /* Got a byte.  */
> +    if (s->rx_fifo_len >= sizeof(s->rx_fifo)) {
> +        printf("WARNING: UART dropped char.\n");
> +        return;
> +    }
> +    s->rx_fifo[s->rx_fifo_len++] = *buf;
> +
> +    update_irq(s);
> +}
> +
> +static int uart_can_rx(void *opaque)
> +{
> +    SiFiveUARTState *s = opaque;
> +
> +    return s->rx_fifo_len < sizeof(s->rx_fifo);
> +}
> +
> +static void uart_event(void *opaque, int event)
> +{
> +}
> +
> +static int uart_be_change(void *opaque)
> +{
> +    SiFiveUARTState *s = opaque;
> +
> +    qemu_chr_fe_set_handlers(&s->chr, uart_can_rx, uart_rx, uart_event,
> +        uart_be_change, s, NULL, true);
> +
> +    return 0;
> +}
> +
> +/*
> + * Create UART device.
> + */
> +SiFiveUARTState *sifive_uart_create(MemoryRegion *address_space, hwaddr base,
> +    Chardev *chr, qemu_irq irq)
> +{
> +    SiFiveUARTState *s = g_malloc0(sizeof(SiFiveUARTState));
> +    s->irq = irq;
> +    qemu_chr_fe_init(&s->chr, chr, &error_abort);
> +    qemu_chr_fe_set_handlers(&s->chr, uart_can_rx, uart_rx, uart_event,
> +        uart_be_change, s, NULL, true);
> +    memory_region_init_io(&s->mmio, NULL, &uart_ops, s,
> +                          TYPE_SIFIVE_UART, SIFIVE_UART_MAX);
> +    memory_region_add_subregion(address_space, base, &s->mmio);
> +    return s;
> +}
> diff --git a/include/hw/riscv/sifive_uart.h b/include/hw/riscv/sifive_uart.h
> new file mode 100644
> index 0000000..1ab0106
> --- /dev/null
> +++ b/include/hw/riscv/sifive_uart.h
> @@ -0,0 +1,76 @@
> +/*
> + * SiFive UART interface
> + *
> + * Copyright (c) 2017 SiFive, Inc.
> + *
> + * Permission is hereby granted, free of charge, to any person obtaining a copy
> + * of this software and associated documentation files (the "Software"), to deal
> + * in the Software without restriction, including without limitation the rights
> + * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
> + * copies of the Software, and to permit persons to whom the Software is
> + * furnished to do so, subject to the following conditions:
> + *
> + * The above copyright notice and this permission notice shall be included in
> + * all copies or substantial portions of the Software.
> + *
> + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
> + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
> + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
> + * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
> + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
> + * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
> + * THE SOFTWARE.
> + */
> +
> +#ifndef HW_SIFIVE_UART_H
> +#define HW_SIFIVE_UART_H
> +
> +enum {
> +    SIFIVE_UART_TXFIFO        = 0,
> +    SIFIVE_UART_RXFIFO        = 4,
> +    SIFIVE_UART_TXCTRL        = 8,
> +    SIFIVE_UART_TXMARK        = 10,
> +    SIFIVE_UART_RXCTRL        = 12,
> +    SIFIVE_UART_RXMARK        = 14,
> +    SIFIVE_UART_IE            = 16,
> +    SIFIVE_UART_IP            = 20,
> +    SIFIVE_UART_DIV           = 24,
> +    SIFIVE_UART_MAX           = 32
> +};
> +
> +enum {
> +    SIFIVE_UART_IE_TXWM       = 1, /* Transmit watermark interrupt enable */
> +    SIFIVE_UART_IE_RXWM       = 2  /* Receive watermark interrupt enable */
> +};
> +
> +enum {
> +    SIFIVE_UART_IP_TXWM       = 1, /* Transmit watermark interrupt pending */
> +    SIFIVE_UART_IP_RXWM       = 2  /* Receive watermark interrupt pending */
> +};
> +
> +#define TYPE_SIFIVE_UART "riscv.sifive.uart"
> +
> +#define SIFIVE_UART(obj) \
> +    OBJECT_CHECK(SiFiveUARTState, (obj), TYPE_SIFIVE_UART)
> +
> +typedef struct SiFiveUARTState {
> +    /*< private >*/
> +    SysBusDevice parent_obj;
> +
> +    /*< public >*/
> +    qemu_irq irq;
> +    MemoryRegion mmio;
> +    CharBackend chr;
> +    uint8_t rx_fifo[8];
> +    unsigned int rx_fifo_len;
> +    uint32_t ie;
> +    uint32_t ip;
> +    uint32_t txctrl;
> +    uint32_t rxctrl;
> +    uint32_t div;
> +} SiFiveUARTState;
> +
> +SiFiveUARTState *sifive_uart_create(MemoryRegion *address_space, hwaddr base,
> +    Chardev *chr, qemu_irq irq);
> +
> +#endif
> -- 
> 2.7.0
> 
> 


-- 
Best regards,
  Antony Pavlov