hw/riscv/sifive_uart.c

   1 /*
   2  * QEMU model of the UART on the SiFive E300 and U500 series SOCs.
   3  *
   4  * Copyright (c) 2016 Stefan O'Rear
   5  *
   6  * This program is free software; you can redistribute it and/or modify it
   7  * under the terms and conditions of the GNU General Public License,
   8  * version 2 or later, as published by the Free Software Foundation.
   9  *
  10  * This program is distributed in the hope it will be useful, but WITHOUT
  11  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  12  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
  13  * more details.
  14  *
  15  * You should have received a copy of the GNU General Public License along with
  16  * this program.  If not, see <http://www.gnu.org/licenses/>.
  17  */
  18
  19 #include "qemu/osdep.h"
  20 #include "qapi/error.h"
  21 #include "qemu/log.h"
  22 #include "hw/sysbus.h"
  23 #include "chardev/char.h"
  24 #include "chardev/char-fe.h"
  25 #include "hw/hw.h"
  26 #include "hw/irq.h"
  27 #include "hw/riscv/sifive_uart.h"
  28
  29 /*
  30  * Not yet implemented:
  31  *
  32  * Transmit FIFO using "qemu/fifo8.h"
  33  */
  34
  35 /* Returns the state of the IP (interrupt pending) register */
  36 static uint64_t uart_ip(SiFiveUARTState *s)
  37 {
  38     uint64_t ret = 0;
  39
  40     uint64_t txcnt = SIFIVE_UART_GET_TXCNT(s->txctrl);
  41     uint64_t rxcnt = SIFIVE_UART_GET_RXCNT(s->rxctrl);
  42
  43     if (txcnt != 0) {
  44         ret |= SIFIVE_UART_IP_TXWM;
  45     }
  46     if (s->rx_fifo_len > rxcnt) {
  47         ret |= SIFIVE_UART_IP_RXWM;
  48     }
  49
  50     return ret;
  51 }
  52
  53 static void update_irq(SiFiveUARTState *s)
  54 {
  55     int cond = 0;
  56     if ((s->ie & SIFIVE_UART_IE_TXWM) ||
  57         ((s->ie & SIFIVE_UART_IE_RXWM) && s->rx_fifo_len)) {
  58         cond = 1;
  59     }
  60     if (cond) {
  61         qemu_irq_raise(s->irq);
  62     } else {
  63         qemu_irq_lower(s->irq);
  64     }
  65 }
  66
  67 static uint64_t
  68 uart_read(void *opaque, hwaddr addr, unsigned int size)
  69 {
  70     SiFiveUARTState *s = opaque;
  71     unsigned char r;
  72     switch (addr) {
  73     case SIFIVE_UART_RXFIFO:
  74         if (s->rx_fifo_len) {
  75             r = s->rx_fifo[0];
  76             memmove(s->rx_fifo, s->rx_fifo + 1, s->rx_fifo_len - 1);
  77             s->rx_fifo_len--;
  78             qemu_chr_fe_accept_input(&s->chr);
  79             update_irq(s);
  80             return r;
  81         }
  82         return 0x80000000;
  83
  84     case SIFIVE_UART_TXFIFO:
  85         return 0; /* Should check tx fifo */
  86     case SIFIVE_UART_IE:
  87         return s->ie;
  88     case SIFIVE_UART_IP:
  89         return uart_ip(s);
  90     case SIFIVE_UART_TXCTRL:
  91         return s->txctrl;
  92     case SIFIVE_UART_RXCTRL:
  93         return s->rxctrl;
  94     case SIFIVE_UART_DIV:
  95         return s->div;
  96     }
  97
  98     qemu_log_mask(LOG_GUEST_ERROR, "%s: bad read: addr=0x%x\n",
  99                   __func__, (int)addr);
 100     return 0;
 101 }
 102
 103 static void
 104 uart_write(void *opaque, hwaddr addr,
 105            uint64_t val64, unsigned int size)
 106 {
 107     SiFiveUARTState *s = opaque;
 108     uint32_t value = val64;
 109     unsigned char ch = value;
 110
 111     switch (addr) {
 112     case SIFIVE_UART_TXFIFO:
 113         qemu_chr_fe_write(&s->chr, &ch, 1);
 114         update_irq(s);
 115         return;
 116     case SIFIVE_UART_IE:
 117         s->ie = val64;
 118         update_irq(s);
 119         return;
 120     case SIFIVE_UART_TXCTRL:
 121         s->txctrl = val64;
 122         return;
 123     case SIFIVE_UART_RXCTRL:
 124         s->rxctrl = val64;
 125         return;
 126     case SIFIVE_UART_DIV:
 127         s->div = val64;
 128         return;
 129     }
 130     qemu_log_mask(LOG_GUEST_ERROR, "%s: bad write: addr=0x%x v=0x%x\n",
 131                   __func__, (int)addr, (int)value);
 132 }
 133
 134 static const MemoryRegionOps uart_ops = {
 135     .read = uart_read,
 136     .write = uart_write,
 137     .endianness = DEVICE_NATIVE_ENDIAN,
 138     .valid = {
 139         .min_access_size = 4,
 140         .max_access_size = 4
 141     }
 142 };
 143
 144 static void uart_rx(void *opaque, const uint8_t *buf, int size)
 145 {
 146     SiFiveUARTState *s = opaque;
 147
 148     /* Got a byte.  */
 149     if (s->rx_fifo_len >= sizeof(s->rx_fifo)) {
 150         printf("WARNING: UART dropped char.\n");
 151         return;
 152     }
 153     s->rx_fifo[s->rx_fifo_len++] = *buf;
 154
 155     update_irq(s);
 156 }
 157
 158 static int uart_can_rx(void *opaque)
 159 {
 160     SiFiveUARTState *s = opaque;
 161
 162     return s->rx_fifo_len < sizeof(s->rx_fifo);
 163 }
 164
 165 static void uart_event(void *opaque, int event)
 166 {
 167 }
 168
 169 static int uart_be_change(void *opaque)
 170 {
 171     SiFiveUARTState *s = opaque;
 172
 173     qemu_chr_fe_set_handlers(&s->chr, uart_can_rx, uart_rx, uart_event,
 174         uart_be_change, s, NULL, true);
 175
 176     return 0;
 177 }
 178
 179 /*
 180  * Create UART device.
 181  */
 182 SiFiveUARTState *sifive_uart_create(MemoryRegion *address_space, hwaddr base,
 183     Chardev *chr, qemu_irq irq)
 184 {
 185     SiFiveUARTState *s = g_malloc0(sizeof(SiFiveUARTState));
 186     s->irq = irq;
 187     qemu_chr_fe_init(&s->chr, chr, &error_abort);
 188     qemu_chr_fe_set_handlers(&s->chr, uart_can_rx, uart_rx, uart_event,
 189         uart_be_change, s, NULL, true);
 190     memory_region_init_io(&s->mmio, NULL, &uart_ops, s,
 191                           TYPE_SIFIVE_UART, SIFIVE_UART_MAX);
 192     memory_region_add_subregion(address_space, base, &s->mmio);
 193     return s;
 194 }