hw/char/ibex_uart.c - qemu - Git at Google

 /*
  * QEMU lowRISC Ibex UART device
  *
  * Copyright (c) 2020 Western Digital
  *
  * For details check the documentation here:
  *    https://docs.opentitan.org/hw/ip/uart/doc/
  *
  * 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 "hw/char/ibex_uart.h"
 #include "hw/irq.h"
 #include "hw/qdev-clock.h"
 #include "hw/qdev-properties.h"
 #include "hw/qdev-properties-system.h"
 #include "migration/vmstate.h"
 #include "qemu/log.h"
 #include "qemu/module.h"

 static void ibex_uart_update_irqs(IbexUartState *s)
 {
     if (s->uart_intr_state & s->uart_intr_enable & R_INTR_STATE_TX_WATERMARK_MASK) {
         qemu_set_irq(s->tx_watermark, 1);
     } else {
         qemu_set_irq(s->tx_watermark, 0);
     }

     if (s->uart_intr_state & s->uart_intr_enable & R_INTR_STATE_RX_WATERMARK_MASK) {
         qemu_set_irq(s->rx_watermark, 1);
     } else {
         qemu_set_irq(s->rx_watermark, 0);
     }

     if (s->uart_intr_state & s->uart_intr_enable & R_INTR_STATE_TX_EMPTY_MASK) {
         qemu_set_irq(s->tx_empty, 1);
     } else {
         qemu_set_irq(s->tx_empty, 0);
     }

     if (s->uart_intr_state & s->uart_intr_enable & R_INTR_STATE_RX_OVERFLOW_MASK) {
         qemu_set_irq(s->rx_overflow, 1);
     } else {
         qemu_set_irq(s->rx_overflow, 0);
     }
 }

 static int ibex_uart_can_receive(void *opaque)
 {
     IbexUartState *s = opaque;

     if ((s->uart_ctrl & R_CTRL_RX_ENABLE_MASK)
            && !(s->uart_status & R_STATUS_RXFULL_MASK)) {
         return 1;
     }

     return 0;
 }

 static void ibex_uart_receive(void *opaque, const uint8_t *buf, int size)
 {
     IbexUartState *s = opaque;
     uint8_t rx_fifo_level = (s->uart_fifo_ctrl & R_FIFO_CTRL_RXILVL_MASK)
                             >> R_FIFO_CTRL_RXILVL_SHIFT;

     s->uart_rdata = *buf;

     s->uart_status &= ~R_STATUS_RXIDLE_MASK;
     s->uart_status &= ~R_STATUS_RXEMPTY_MASK;
     /* The RXFULL is set after receiving a single byte
      * as the FIFO buffers are not yet implemented.
      */
     s->uart_status |= R_STATUS_RXFULL_MASK;
     s->rx_level += 1;

     if (size > rx_fifo_level) {
         s->uart_intr_state |= R_INTR_STATE_RX_WATERMARK_MASK;
     }

     ibex_uart_update_irqs(s);
 }

 static gboolean ibex_uart_xmit(GIOChannel *chan, GIOCondition cond,
                                void *opaque)
 {
     IbexUartState *s = opaque;
     uint8_t tx_fifo_level = (s->uart_fifo_ctrl & R_FIFO_CTRL_TXILVL_MASK)
                             >> R_FIFO_CTRL_TXILVL_SHIFT;
     int ret;

     /* instant drain the fifo when there's no back-end */
     if (!qemu_chr_fe_backend_connected(&s->chr)) {
         s->tx_level = 0;
         return FALSE;
     }

     if (!s->tx_level) {
         s->uart_status &= ~R_STATUS_TXFULL_MASK;
         s->uart_status |= R_STATUS_TXEMPTY_MASK;
         s->uart_intr_state |= R_INTR_STATE_TX_EMPTY_MASK;
         s->uart_intr_state &= ~R_INTR_STATE_TX_WATERMARK_MASK;
         ibex_uart_update_irqs(s);
         return FALSE;
     }

     ret = qemu_chr_fe_write(&s->chr, s->tx_fifo, s->tx_level);

     if (ret >= 0) {
         s->tx_level -= ret;
         memmove(s->tx_fifo, s->tx_fifo + ret, s->tx_level);
     }

     if (s->tx_level) {
         guint r = qemu_chr_fe_add_watch(&s->chr, G_IO_OUT | G_IO_HUP,
                                         ibex_uart_xmit, s);
         if (!r) {
             s->tx_level = 0;
             return FALSE;
         }
     }

     /* Clear the TX Full bit */
     if (s->tx_level != IBEX_UART_TX_FIFO_SIZE) {
         s->uart_status &= ~R_STATUS_TXFULL_MASK;
     }

     /* Disable the TX_WATERMARK IRQ */
     if (s->tx_level < tx_fifo_level) {
         s->uart_intr_state &= ~R_INTR_STATE_TX_WATERMARK_MASK;
     }

     /* Set TX empty */
     if (s->tx_level == 0) {
         s->uart_status |= R_STATUS_TXEMPTY_MASK;
         s->uart_intr_state |= R_INTR_STATE_TX_EMPTY_MASK;
     }

     ibex_uart_update_irqs(s);
     return FALSE;
 }

 static void uart_write_tx_fifo(IbexUartState *s, const uint8_t *buf,
                                int size)
 {
     uint64_t current_time = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
     uint8_t tx_fifo_level = (s->uart_fifo_ctrl & R_FIFO_CTRL_TXILVL_MASK)
                             >> R_FIFO_CTRL_TXILVL_SHIFT;

     if (size > IBEX_UART_TX_FIFO_SIZE - s->tx_level) {
         size = IBEX_UART_TX_FIFO_SIZE - s->tx_level;
         qemu_log_mask(LOG_GUEST_ERROR, "ibex_uart: TX FIFO overflow");
     }

     memcpy(s->tx_fifo + s->tx_level, buf, size);
     s->tx_level += size;

     if (s->tx_level > 0) {
         s->uart_status &= ~R_STATUS_TXEMPTY_MASK;
     }

     if (s->tx_level >= tx_fifo_level) {
         s->uart_intr_state |= R_INTR_STATE_TX_WATERMARK_MASK;
         ibex_uart_update_irqs(s);
     }

     if (s->tx_level == IBEX_UART_TX_FIFO_SIZE) {
         s->uart_status |= R_STATUS_TXFULL_MASK;
     }

     timer_mod(s->fifo_trigger_handle, current_time +
               (s->char_tx_time * 4));
 }

 static void ibex_uart_reset(DeviceState *dev)
 {
     IbexUartState *s = IBEX_UART(dev);

     s->uart_intr_state = 0x00000000;
     s->uart_intr_state = 0x00000000;
     s->uart_intr_enable = 0x00000000;
     s->uart_ctrl = 0x00000000;
     s->uart_status = 0x0000003c;
     s->uart_rdata = 0x00000000;
     s->uart_fifo_ctrl = 0x00000000;
     s->uart_fifo_status = 0x00000000;
     s->uart_ovrd = 0x00000000;
     s->uart_val = 0x00000000;
     s->uart_timeout_ctrl = 0x00000000;

     s->tx_level = 0;
     s->rx_level = 0;

     s->char_tx_time = (NANOSECONDS_PER_SECOND / 230400) * 10;

     ibex_uart_update_irqs(s);
 }

 static uint64_t ibex_uart_get_baud(IbexUartState *s)
 {
     uint64_t baud;

     baud = ((s->uart_ctrl & R_CTRL_NCO_MASK) >> 16);
     baud *= clock_get_hz(s->f_clk);
     baud >>= 20;

     return baud;
 }

 static uint64_t ibex_uart_read(void *opaque, hwaddr addr,
                                        unsigned int size)
 {
     IbexUartState *s = opaque;
     uint64_t retvalue = 0;

     switch (addr >> 2) {
     case R_INTR_STATE:
         retvalue = s->uart_intr_state;
         break;
     case R_INTR_ENABLE:
         retvalue = s->uart_intr_enable;
         break;
     case R_INTR_TEST:
         qemu_log_mask(LOG_GUEST_ERROR,
                       "%s: wdata is write only\n", __func__);
         break;

     case R_CTRL:
         retvalue = s->uart_ctrl;
         break;
     case R_STATUS:
         retvalue = s->uart_status;
         break;

     case R_RDATA:
         retvalue = s->uart_rdata;
         if ((s->uart_ctrl & R_CTRL_RX_ENABLE_MASK) && (s->rx_level > 0)) {
             qemu_chr_fe_accept_input(&s->chr);

             s->rx_level -= 1;
             s->uart_status &= ~R_STATUS_RXFULL_MASK;
             if (s->rx_level == 0) {
                 s->uart_status |= R_STATUS_RXIDLE_MASK;
                 s->uart_status |= R_STATUS_RXEMPTY_MASK;
             }
         }
         break;
     case R_WDATA:
         qemu_log_mask(LOG_GUEST_ERROR,
                       "%s: wdata is write only\n", __func__);
         break;

     case R_FIFO_CTRL:
         retvalue = s->uart_fifo_ctrl;
         break;
     case R_FIFO_STATUS:
         retvalue = s->uart_fifo_status;

         retvalue |= (s->rx_level & 0x1F) << R_FIFO_STATUS_RXLVL_SHIFT;
         retvalue |= (s->tx_level & 0x1F) << R_FIFO_STATUS_TXLVL_SHIFT;

         qemu_log_mask(LOG_UNIMP,
                       "%s: RX fifos are not supported\n", __func__);
         break;

     case R_OVRD:
         retvalue = s->uart_ovrd;
         qemu_log_mask(LOG_UNIMP,
                       "%s: ovrd is not supported\n", __func__);
         break;
     case R_VAL:
         retvalue = s->uart_val;
         qemu_log_mask(LOG_UNIMP,
                       "%s: val is not supported\n", __func__);
         break;
     case R_TIMEOUT_CTRL:
         retvalue = s->uart_timeout_ctrl;
         qemu_log_mask(LOG_UNIMP,
                       "%s: timeout_ctrl is not supported\n", __func__);
         break;
     default:
         qemu_log_mask(LOG_GUEST_ERROR,
                       "%s: Bad offset 0x%"HWADDR_PRIx"\n", __func__, addr);
         return 0;
     }

     return retvalue;
 }

 static void ibex_uart_write(void *opaque, hwaddr addr,
                                   uint64_t val64, unsigned int size)
 {
     IbexUartState *s = opaque;
     uint32_t value = val64;

     switch (addr >> 2) {
     case R_INTR_STATE:
         /* Write 1 clear */
         s->uart_intr_state &= ~value;
         ibex_uart_update_irqs(s);
         break;
     case R_INTR_ENABLE:
         s->uart_intr_enable = value;
         ibex_uart_update_irqs(s);
         break;
     case R_INTR_TEST:
         s->uart_intr_state |= value;
         ibex_uart_update_irqs(s);
         break;

     case R_CTRL:
         s->uart_ctrl = value;

         if (value & R_CTRL_NF_MASK) {
             qemu_log_mask(LOG_UNIMP,
                           "%s: UART_CTRL_NF is not supported\n", __func__);
         }
         if (value & R_CTRL_SLPBK_MASK) {
             qemu_log_mask(LOG_UNIMP,
                           "%s: UART_CTRL_SLPBK is not supported\n", __func__);
         }
         if (value & R_CTRL_LLPBK_MASK) {
             qemu_log_mask(LOG_UNIMP,
                           "%s: UART_CTRL_LLPBK is not supported\n", __func__);
         }
         if (value & R_CTRL_PARITY_EN_MASK) {
             qemu_log_mask(LOG_UNIMP,
                           "%s: UART_CTRL_PARITY_EN is not supported\n",
                           __func__);
         }
         if (value & R_CTRL_PARITY_ODD_MASK) {
             qemu_log_mask(LOG_UNIMP,
                           "%s: UART_CTRL_PARITY_ODD is not supported\n",
                           __func__);
         }
         if (value & R_CTRL_RXBLVL_MASK) {
             qemu_log_mask(LOG_UNIMP,
                           "%s: UART_CTRL_RXBLVL is not supported\n", __func__);
         }
         if (value & R_CTRL_NCO_MASK) {
             uint64_t baud = ibex_uart_get_baud(s);

             s->char_tx_time = (NANOSECONDS_PER_SECOND / baud) * 10;
         }
         break;
     case R_STATUS:
         qemu_log_mask(LOG_GUEST_ERROR,
                       "%s: status is read only\n", __func__);
         break;

     case R_RDATA:
         qemu_log_mask(LOG_GUEST_ERROR,
                       "%s: rdata is read only\n", __func__);
         break;
     case R_WDATA:
         uart_write_tx_fifo(s, (uint8_t *) &value, 1);
         break;

     case R_FIFO_CTRL:
         s->uart_fifo_ctrl = value;

         if (value & R_FIFO_CTRL_RXRST_MASK) {
             s->rx_level = 0;
             qemu_log_mask(LOG_UNIMP,
                           "%s: RX fifos are not supported\n", __func__);
         }
         if (value & R_FIFO_CTRL_TXRST_MASK) {
             s->tx_level = 0;
         }
         break;
     case R_FIFO_STATUS:
         qemu_log_mask(LOG_GUEST_ERROR,
                       "%s: fifo_status is read only\n", __func__);
         break;

     case R_OVRD:
         s->uart_ovrd = value;
         qemu_log_mask(LOG_UNIMP,
                       "%s: ovrd is not supported\n", __func__);
         break;
     case R_VAL:
         qemu_log_mask(LOG_GUEST_ERROR,
                       "%s: val is read only\n", __func__);
         break;
     case R_TIMEOUT_CTRL:
         s->uart_timeout_ctrl = value;
         qemu_log_mask(LOG_UNIMP,
                       "%s: timeout_ctrl is not supported\n", __func__);
         break;
     default:
         qemu_log_mask(LOG_GUEST_ERROR,
                       "%s: Bad offset 0x%"HWADDR_PRIx"\n", __func__, addr);
     }
 }

 static void ibex_uart_clk_update(void *opaque, ClockEvent event)
 {
     IbexUartState *s = opaque;

     /* recompute uart's speed on clock change */
     uint64_t baud = ibex_uart_get_baud(s);

     s->char_tx_time = (NANOSECONDS_PER_SECOND / baud) * 10;
 }

 static void fifo_trigger_update(void *opaque)
 {
     IbexUartState *s = opaque;

     if (s->uart_ctrl & R_CTRL_TX_ENABLE_MASK) {
         ibex_uart_xmit(NULL, G_IO_OUT, s);
     }
 }

 static const MemoryRegionOps ibex_uart_ops = {
     .read = ibex_uart_read,
     .write = ibex_uart_write,
     .endianness = DEVICE_NATIVE_ENDIAN,
     .impl.min_access_size = 4,
     .impl.max_access_size = 4,
 };

 static int ibex_uart_post_load(void *opaque, int version_id)
 {
     IbexUartState *s = opaque;

     ibex_uart_update_irqs(s);
     return 0;
 }

 static const VMStateDescription vmstate_ibex_uart = {
     .name = TYPE_IBEX_UART,
     .version_id = 1,
     .minimum_version_id = 1,
     .post_load = ibex_uart_post_load,
     .fields = (VMStateField[]) {
         VMSTATE_UINT8_ARRAY(tx_fifo, IbexUartState,
                             IBEX_UART_TX_FIFO_SIZE),
         VMSTATE_UINT32(tx_level, IbexUartState),
         VMSTATE_UINT64(char_tx_time, IbexUartState),
         VMSTATE_TIMER_PTR(fifo_trigger_handle, IbexUartState),
         VMSTATE_UINT32(uart_intr_state, IbexUartState),
         VMSTATE_UINT32(uart_intr_enable, IbexUartState),
         VMSTATE_UINT32(uart_ctrl, IbexUartState),
         VMSTATE_UINT32(uart_status, IbexUartState),
         VMSTATE_UINT32(uart_rdata, IbexUartState),
         VMSTATE_UINT32(uart_fifo_ctrl, IbexUartState),
         VMSTATE_UINT32(uart_fifo_status, IbexUartState),
         VMSTATE_UINT32(uart_ovrd, IbexUartState),
         VMSTATE_UINT32(uart_val, IbexUartState),
         VMSTATE_UINT32(uart_timeout_ctrl, IbexUartState),
         VMSTATE_END_OF_LIST()
     }
 };

 static Property ibex_uart_properties[] = {
     DEFINE_PROP_CHR("chardev", IbexUartState, chr),
     DEFINE_PROP_END_OF_LIST(),
 };

 static void ibex_uart_init(Object *obj)
 {
     IbexUartState *s = IBEX_UART(obj);

     s->f_clk = qdev_init_clock_in(DEVICE(obj), "f_clock",
                                   ibex_uart_clk_update, s, ClockUpdate);
     clock_set_hz(s->f_clk, IBEX_UART_CLOCK);

     sysbus_init_irq(SYS_BUS_DEVICE(obj), &s->tx_watermark);
     sysbus_init_irq(SYS_BUS_DEVICE(obj), &s->rx_watermark);
     sysbus_init_irq(SYS_BUS_DEVICE(obj), &s->tx_empty);
     sysbus_init_irq(SYS_BUS_DEVICE(obj), &s->rx_overflow);

     memory_region_init_io(&s->mmio, obj, &ibex_uart_ops, s,
                           TYPE_IBEX_UART, 0x400);
     sysbus_init_mmio(SYS_BUS_DEVICE(obj), &s->mmio);
 }

 static void ibex_uart_realize(DeviceState *dev, Error **errp)
 {
     IbexUartState *s = IBEX_UART(dev);

     s->fifo_trigger_handle = timer_new_ns(QEMU_CLOCK_VIRTUAL,
                                           fifo_trigger_update, s);

     qemu_chr_fe_set_handlers(&s->chr, ibex_uart_can_receive,
                              ibex_uart_receive, NULL, NULL,
                              s, NULL, true);
 }

 static void ibex_uart_class_init(ObjectClass *klass, void *data)
 {
     DeviceClass *dc = DEVICE_CLASS(klass);

     dc->reset = ibex_uart_reset;
     dc->realize = ibex_uart_realize;
     dc->vmsd = &vmstate_ibex_uart;
     device_class_set_props(dc, ibex_uart_properties);
 }

 static const TypeInfo ibex_uart_info = {
     .name          = TYPE_IBEX_UART,
     .parent        = TYPE_SYS_BUS_DEVICE,
     .instance_size = sizeof(IbexUartState),
     .instance_init = ibex_uart_init,
     .class_init    = ibex_uart_class_init,
 };

 static void ibex_uart_register_types(void)
 {
     type_register_static(&ibex_uart_info);
 }

 type_init(ibex_uart_register_types)
	/*
	* QEMU lowRISC Ibex UART device
	*
	* Copyright (c) 2020 Western Digital
	*
	* For details check the documentation here:
	* https://docs.opentitan.org/hw/ip/uart/doc/
	*
	* 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 "hw/char/ibex_uart.h"
	#include "hw/irq.h"
	#include "hw/qdev-clock.h"
	#include "hw/qdev-properties.h"
	#include "hw/qdev-properties-system.h"
	#include "migration/vmstate.h"
	#include "qemu/log.h"
	#include "qemu/module.h"

	static void ibex_uart_update_irqs(IbexUartState *s)
	{
	if (s->uart_intr_state & s->uart_intr_enable & R_INTR_STATE_TX_WATERMARK_MASK) {
	qemu_set_irq(s->tx_watermark, 1);
	} else {
	qemu_set_irq(s->tx_watermark, 0);
	}

	if (s->uart_intr_state & s->uart_intr_enable & R_INTR_STATE_RX_WATERMARK_MASK) {
	qemu_set_irq(s->rx_watermark, 1);
	} else {
	qemu_set_irq(s->rx_watermark, 0);
	}

	if (s->uart_intr_state & s->uart_intr_enable & R_INTR_STATE_TX_EMPTY_MASK) {
	qemu_set_irq(s->tx_empty, 1);
	} else {
	qemu_set_irq(s->tx_empty, 0);
	}

	if (s->uart_intr_state & s->uart_intr_enable & R_INTR_STATE_RX_OVERFLOW_MASK) {
	qemu_set_irq(s->rx_overflow, 1);
	} else {
	qemu_set_irq(s->rx_overflow, 0);
	}
	}

	static int ibex_uart_can_receive(void *opaque)
	{
	IbexUartState *s = opaque;

	if ((s->uart_ctrl & R_CTRL_RX_ENABLE_MASK)
	&& !(s->uart_status & R_STATUS_RXFULL_MASK)) {
	return 1;
	}

	return 0;
	}

	static void ibex_uart_receive(void opaque, const uint8_t buf, int size)
	{
	IbexUartState *s = opaque;
	uint8_t rx_fifo_level = (s->uart_fifo_ctrl & R_FIFO_CTRL_RXILVL_MASK)
	>> R_FIFO_CTRL_RXILVL_SHIFT;

	s->uart_rdata = *buf;

	s->uart_status &= ~R_STATUS_RXIDLE_MASK;
	s->uart_status &= ~R_STATUS_RXEMPTY_MASK;
	/* The RXFULL is set after receiving a single byte
	* as the FIFO buffers are not yet implemented.
	*/
	s->uart_status \|= R_STATUS_RXFULL_MASK;
	s->rx_level += 1;

	if (size > rx_fifo_level) {
	s->uart_intr_state \|= R_INTR_STATE_RX_WATERMARK_MASK;
	}

	ibex_uart_update_irqs(s);
	}

	static gboolean ibex_uart_xmit(GIOChannel *chan, GIOCondition cond,
	void *opaque)
	{
	IbexUartState *s = opaque;
	uint8_t tx_fifo_level = (s->uart_fifo_ctrl & R_FIFO_CTRL_TXILVL_MASK)
	>> R_FIFO_CTRL_TXILVL_SHIFT;
	int ret;

	/* instant drain the fifo when there's no back-end */
	if (!qemu_chr_fe_backend_connected(&s->chr)) {
	s->tx_level = 0;
	return FALSE;
	}

	if (!s->tx_level) {
	s->uart_status &= ~R_STATUS_TXFULL_MASK;
	s->uart_status \|= R_STATUS_TXEMPTY_MASK;
	s->uart_intr_state \|= R_INTR_STATE_TX_EMPTY_MASK;
	s->uart_intr_state &= ~R_INTR_STATE_TX_WATERMARK_MASK;
	ibex_uart_update_irqs(s);
	return FALSE;
	}

	ret = qemu_chr_fe_write(&s->chr, s->tx_fifo, s->tx_level);

	if (ret >= 0) {
	s->tx_level -= ret;
	memmove(s->tx_fifo, s->tx_fifo + ret, s->tx_level);
	}

	if (s->tx_level) {
	guint r = qemu_chr_fe_add_watch(&s->chr, G_IO_OUT \| G_IO_HUP,
	ibex_uart_xmit, s);
	if (!r) {
	s->tx_level = 0;
	return FALSE;
	}
	}

	/* Clear the TX Full bit */
	if (s->tx_level != IBEX_UART_TX_FIFO_SIZE) {
	s->uart_status &= ~R_STATUS_TXFULL_MASK;
	}

	/* Disable the TX_WATERMARK IRQ */
	if (s->tx_level < tx_fifo_level) {
	s->uart_intr_state &= ~R_INTR_STATE_TX_WATERMARK_MASK;
	}

	/* Set TX empty */
	if (s->tx_level == 0) {
	s->uart_status \|= R_STATUS_TXEMPTY_MASK;
	s->uart_intr_state \|= R_INTR_STATE_TX_EMPTY_MASK;
	}

	ibex_uart_update_irqs(s);
	return FALSE;
	}

	static void uart_write_tx_fifo(IbexUartState s, const uint8_t buf,
	int size)
	{
	uint64_t current_time = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
	uint8_t tx_fifo_level = (s->uart_fifo_ctrl & R_FIFO_CTRL_TXILVL_MASK)
	>> R_FIFO_CTRL_TXILVL_SHIFT;

	if (size > IBEX_UART_TX_FIFO_SIZE - s->tx_level) {
	size = IBEX_UART_TX_FIFO_SIZE - s->tx_level;
	qemu_log_mask(LOG_GUEST_ERROR, "ibex_uart: TX FIFO overflow");
	}

	memcpy(s->tx_fifo + s->tx_level, buf, size);
	s->tx_level += size;

	if (s->tx_level > 0) {
	s->uart_status &= ~R_STATUS_TXEMPTY_MASK;
	}

	if (s->tx_level >= tx_fifo_level) {
	s->uart_intr_state \|= R_INTR_STATE_TX_WATERMARK_MASK;
	ibex_uart_update_irqs(s);
	}

	if (s->tx_level == IBEX_UART_TX_FIFO_SIZE) {
	s->uart_status \|= R_STATUS_TXFULL_MASK;
	}

	timer_mod(s->fifo_trigger_handle, current_time +
	(s->char_tx_time * 4));
	}

	static void ibex_uart_reset(DeviceState *dev)
	{
	IbexUartState *s = IBEX_UART(dev);

	s->uart_intr_state = 0x00000000;
	s->uart_intr_state = 0x00000000;
	s->uart_intr_enable = 0x00000000;
	s->uart_ctrl = 0x00000000;
	s->uart_status = 0x0000003c;
	s->uart_rdata = 0x00000000;
	s->uart_fifo_ctrl = 0x00000000;
	s->uart_fifo_status = 0x00000000;
	s->uart_ovrd = 0x00000000;
	s->uart_val = 0x00000000;
	s->uart_timeout_ctrl = 0x00000000;

	s->tx_level = 0;
	s->rx_level = 0;

	s->char_tx_time = (NANOSECONDS_PER_SECOND / 230400) * 10;

	ibex_uart_update_irqs(s);
	}

	static uint64_t ibex_uart_get_baud(IbexUartState *s)
	{
	uint64_t baud;

	baud = ((s->uart_ctrl & R_CTRL_NCO_MASK) >> 16);
	baud *= clock_get_hz(s->f_clk);
	baud >>= 20;

	return baud;
	}

	static uint64_t ibex_uart_read(void *opaque, hwaddr addr,
	unsigned int size)
	{
	IbexUartState *s = opaque;
	uint64_t retvalue = 0;

	switch (addr >> 2) {
	case R_INTR_STATE:
	retvalue = s->uart_intr_state;
	break;
	case R_INTR_ENABLE:
	retvalue = s->uart_intr_enable;
	break;
	case R_INTR_TEST:
	qemu_log_mask(LOG_GUEST_ERROR,
	"%s: wdata is write only\n", __func__);
	break;

	case R_CTRL:
	retvalue = s->uart_ctrl;
	break;
	case R_STATUS:
	retvalue = s->uart_status;
	break;

	case R_RDATA:
	retvalue = s->uart_rdata;
	if ((s->uart_ctrl & R_CTRL_RX_ENABLE_MASK) && (s->rx_level > 0)) {
	qemu_chr_fe_accept_input(&s->chr);

	s->rx_level -= 1;
	s->uart_status &= ~R_STATUS_RXFULL_MASK;
	if (s->rx_level == 0) {
	s->uart_status \|= R_STATUS_RXIDLE_MASK;
	s->uart_status \|= R_STATUS_RXEMPTY_MASK;
	}
	}
	break;
	case R_WDATA:
	qemu_log_mask(LOG_GUEST_ERROR,
	"%s: wdata is write only\n", __func__);
	break;

	case R_FIFO_CTRL:
	retvalue = s->uart_fifo_ctrl;
	break;
	case R_FIFO_STATUS:
	retvalue = s->uart_fifo_status;

	retvalue \|= (s->rx_level & 0x1F) << R_FIFO_STATUS_RXLVL_SHIFT;
	retvalue \|= (s->tx_level & 0x1F) << R_FIFO_STATUS_TXLVL_SHIFT;

	qemu_log_mask(LOG_UNIMP,
	"%s: RX fifos are not supported\n", __func__);
	break;

	case R_OVRD:
	retvalue = s->uart_ovrd;
	qemu_log_mask(LOG_UNIMP,
	"%s: ovrd is not supported\n", __func__);
	break;
	case R_VAL:
	retvalue = s->uart_val;
	qemu_log_mask(LOG_UNIMP,
	"%s: val is not supported\n", __func__);
	break;
	case R_TIMEOUT_CTRL:
	retvalue = s->uart_timeout_ctrl;
	qemu_log_mask(LOG_UNIMP,
	"%s: timeout_ctrl is not supported\n", __func__);
	break;
	default:
	qemu_log_mask(LOG_GUEST_ERROR,
	"%s: Bad offset 0x%"HWADDR_PRIx"\n", __func__, addr);
	return 0;
	}

	return retvalue;
	}

	static void ibex_uart_write(void *opaque, hwaddr addr,
	uint64_t val64, unsigned int size)
	{
	IbexUartState *s = opaque;
	uint32_t value = val64;

	switch (addr >> 2) {
	case R_INTR_STATE:
	/* Write 1 clear */
	s->uart_intr_state &= ~value;
	ibex_uart_update_irqs(s);
	break;
	case R_INTR_ENABLE:
	s->uart_intr_enable = value;
	ibex_uart_update_irqs(s);
	break;
	case R_INTR_TEST:
	s->uart_intr_state \|= value;
	ibex_uart_update_irqs(s);
	break;

	case R_CTRL:
	s->uart_ctrl = value;

	if (value & R_CTRL_NF_MASK) {
	qemu_log_mask(LOG_UNIMP,
	"%s: UART_CTRL_NF is not supported\n", __func__);
	}
	if (value & R_CTRL_SLPBK_MASK) {
	qemu_log_mask(LOG_UNIMP,
	"%s: UART_CTRL_SLPBK is not supported\n", __func__);
	}
	if (value & R_CTRL_LLPBK_MASK) {
	qemu_log_mask(LOG_UNIMP,
	"%s: UART_CTRL_LLPBK is not supported\n", __func__);
	}
	if (value & R_CTRL_PARITY_EN_MASK) {
	qemu_log_mask(LOG_UNIMP,
	"%s: UART_CTRL_PARITY_EN is not supported\n",
	__func__);
	}
	if (value & R_CTRL_PARITY_ODD_MASK) {
	qemu_log_mask(LOG_UNIMP,
	"%s: UART_CTRL_PARITY_ODD is not supported\n",
	__func__);
	}
	if (value & R_CTRL_RXBLVL_MASK) {
	qemu_log_mask(LOG_UNIMP,
	"%s: UART_CTRL_RXBLVL is not supported\n", __func__);
	}
	if (value & R_CTRL_NCO_MASK) {
	uint64_t baud = ibex_uart_get_baud(s);

	s->char_tx_time = (NANOSECONDS_PER_SECOND / baud) * 10;
	}
	break;
	case R_STATUS:
	qemu_log_mask(LOG_GUEST_ERROR,
	"%s: status is read only\n", __func__);
	break;

	case R_RDATA:
	qemu_log_mask(LOG_GUEST_ERROR,
	"%s: rdata is read only\n", __func__);
	break;
	case R_WDATA:
	uart_write_tx_fifo(s, (uint8_t *) &value, 1);
	break;

	case R_FIFO_CTRL:
	s->uart_fifo_ctrl = value;

	if (value & R_FIFO_CTRL_RXRST_MASK) {
	s->rx_level = 0;
	qemu_log_mask(LOG_UNIMP,
	"%s: RX fifos are not supported\n", __func__);
	}
	if (value & R_FIFO_CTRL_TXRST_MASK) {
	s->tx_level = 0;
	}
	break;
	case R_FIFO_STATUS:
	qemu_log_mask(LOG_GUEST_ERROR,
	"%s: fifo_status is read only\n", __func__);
	break;

	case R_OVRD:
	s->uart_ovrd = value;
	qemu_log_mask(LOG_UNIMP,
	"%s: ovrd is not supported\n", __func__);
	break;
	case R_VAL:
	qemu_log_mask(LOG_GUEST_ERROR,
	"%s: val is read only\n", __func__);
	break;
	case R_TIMEOUT_CTRL:
	s->uart_timeout_ctrl = value;
	qemu_log_mask(LOG_UNIMP,
	"%s: timeout_ctrl is not supported\n", __func__);
	break;
	default:
	qemu_log_mask(LOG_GUEST_ERROR,
	"%s: Bad offset 0x%"HWADDR_PRIx"\n", __func__, addr);
	}
	}

	static void ibex_uart_clk_update(void *opaque, ClockEvent event)
	{
	IbexUartState *s = opaque;

	/* recompute uart's speed on clock change */
	uint64_t baud = ibex_uart_get_baud(s);

	s->char_tx_time = (NANOSECONDS_PER_SECOND / baud) * 10;
	}

	static void fifo_trigger_update(void *opaque)
	{
	IbexUartState *s = opaque;

	if (s->uart_ctrl & R_CTRL_TX_ENABLE_MASK) {
	ibex_uart_xmit(NULL, G_IO_OUT, s);
	}
	}

	static const MemoryRegionOps ibex_uart_ops = {
	.read = ibex_uart_read,
	.write = ibex_uart_write,
	.endianness = DEVICE_NATIVE_ENDIAN,
	.impl.min_access_size = 4,
	.impl.max_access_size = 4,
	};

	static int ibex_uart_post_load(void *opaque, int version_id)
	{
	IbexUartState *s = opaque;

	ibex_uart_update_irqs(s);
	return 0;
	}

	static const VMStateDescription vmstate_ibex_uart = {
	.name = TYPE_IBEX_UART,
	.version_id = 1,
	.minimum_version_id = 1,
	.post_load = ibex_uart_post_load,
	.fields = (VMStateField[]) {
	VMSTATE_UINT8_ARRAY(tx_fifo, IbexUartState,
	IBEX_UART_TX_FIFO_SIZE),
	VMSTATE_UINT32(tx_level, IbexUartState),
	VMSTATE_UINT64(char_tx_time, IbexUartState),
	VMSTATE_TIMER_PTR(fifo_trigger_handle, IbexUartState),
	VMSTATE_UINT32(uart_intr_state, IbexUartState),
	VMSTATE_UINT32(uart_intr_enable, IbexUartState),
	VMSTATE_UINT32(uart_ctrl, IbexUartState),
	VMSTATE_UINT32(uart_status, IbexUartState),
	VMSTATE_UINT32(uart_rdata, IbexUartState),
	VMSTATE_UINT32(uart_fifo_ctrl, IbexUartState),
	VMSTATE_UINT32(uart_fifo_status, IbexUartState),
	VMSTATE_UINT32(uart_ovrd, IbexUartState),
	VMSTATE_UINT32(uart_val, IbexUartState),
	VMSTATE_UINT32(uart_timeout_ctrl, IbexUartState),
	VMSTATE_END_OF_LIST()
	}
	};

	static Property ibex_uart_properties[] = {
	DEFINE_PROP_CHR("chardev", IbexUartState, chr),
	DEFINE_PROP_END_OF_LIST(),
	};

	static void ibex_uart_init(Object *obj)
	{
	IbexUartState *s = IBEX_UART(obj);

	s->f_clk = qdev_init_clock_in(DEVICE(obj), "f_clock",
	ibex_uart_clk_update, s, ClockUpdate);
	clock_set_hz(s->f_clk, IBEX_UART_CLOCK);

	sysbus_init_irq(SYS_BUS_DEVICE(obj), &s->tx_watermark);
	sysbus_init_irq(SYS_BUS_DEVICE(obj), &s->rx_watermark);
	sysbus_init_irq(SYS_BUS_DEVICE(obj), &s->tx_empty);
	sysbus_init_irq(SYS_BUS_DEVICE(obj), &s->rx_overflow);

	memory_region_init_io(&s->mmio, obj, &ibex_uart_ops, s,
	TYPE_IBEX_UART, 0x400);
	sysbus_init_mmio(SYS_BUS_DEVICE(obj), &s->mmio);
	}

	static void ibex_uart_realize(DeviceState dev, Error *errp)
	{
	IbexUartState *s = IBEX_UART(dev);

	s->fifo_trigger_handle = timer_new_ns(QEMU_CLOCK_VIRTUAL,
	fifo_trigger_update, s);

	qemu_chr_fe_set_handlers(&s->chr, ibex_uart_can_receive,
	ibex_uart_receive, NULL, NULL,
	s, NULL, true);
	}

	static void ibex_uart_class_init(ObjectClass klass, void data)
	{
	DeviceClass *dc = DEVICE_CLASS(klass);

	dc->reset = ibex_uart_reset;
	dc->realize = ibex_uart_realize;
	dc->vmsd = &vmstate_ibex_uart;
	device_class_set_props(dc, ibex_uart_properties);
	}

	static const TypeInfo ibex_uart_info = {
	.name = TYPE_IBEX_UART,
	.parent = TYPE_SYS_BUS_DEVICE,
	.instance_size = sizeof(IbexUartState),
	.instance_init = ibex_uart_init,
	.class_init = ibex_uart_class_init,
	};

	static void ibex_uart_register_types(void)
	{
	type_register_static(&ibex_uart_info);
	}

	type_init(ibex_uart_register_types)