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qemu/hw/char/imx_serial.c
Rayhan Faizel 988f244297 hw/char/imx_serial: Implement receive FIFO and ageing timer 
This patch implements a 32 half word FIFO as per imx serial device
specifications.  If a non empty FIFO is below the trigger level, an
ageing timer will tick for a duration of 8 characters.  On expiry,
AGTIM will be set triggering an interrupt.  AGTIM timer resets when
there is activity in the receive FIFO.

Otherwise, RRDY is set when trigger level is exceeded.  The receive
trigger level is 8 in newer kernel versions and 1 in older ones.

This change will break migration compatibility for the imx boards.

Signed-off-by: Rayhan Faizel <rayhan.faizel@gmail.com>
Message-id: 20240125151931.83494-1-rayhan.faizel@gmail.com
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
[PMM: commit message tidyups]
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
2024-01-26 11:34:21 +00:00

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/*
* IMX31 UARTS
*
* Copyright (c) 2008 OKL
* Originally Written by Hans Jiang
* Copyright (c) 2011 NICTA Pty Ltd.
* Updated by Jean-Christophe Dubois <jcd@tribudubois.net>
*
* This work is licensed under the terms of the GNU GPL, version 2 or later.
* See the COPYING file in the top-level directory.
*
* This is a `bare-bones' implementation of the IMX series serial ports.
* TODO:
* -- implement FIFOs. The real hardware has 32 word transmit
* and receive FIFOs; we currently use a 1-char buffer
* -- implement DMA
* -- implement BAUD-rate and modem lines, for when the backend
* is a real serial device.
*/
#include "qemu/osdep.h"
#include "hw/char/imx_serial.h"
#include "hw/irq.h"
#include "hw/qdev-properties.h"
#include "hw/qdev-properties-system.h"
#include "migration/vmstate.h"
#include "qemu/log.h"
#include "qemu/module.h"
#include "qemu/fifo32.h"
#ifndef DEBUG_IMX_UART
#define DEBUG_IMX_UART 0
#endif
#define DPRINTF(fmt, args...) \
do { \
if (DEBUG_IMX_UART) { \
fprintf(stderr, "[%s]%s: " fmt , TYPE_IMX_SERIAL, \
__func__, ##args); \
} \
} while (0)
static const VMStateDescription vmstate_imx_serial = {
.name = TYPE_IMX_SERIAL,
.version_id = 3,
.minimum_version_id = 3,
.fields = (const VMStateField[]) {
VMSTATE_FIFO32(rx_fifo, IMXSerialState),
VMSTATE_TIMER(ageing_timer, IMXSerialState),
VMSTATE_UINT32(usr1, IMXSerialState),
VMSTATE_UINT32(usr2, IMXSerialState),
VMSTATE_UINT32(ucr1, IMXSerialState),
VMSTATE_UINT32(uts1, IMXSerialState),
VMSTATE_UINT32(onems, IMXSerialState),
VMSTATE_UINT32(ufcr, IMXSerialState),
VMSTATE_UINT32(ubmr, IMXSerialState),
VMSTATE_UINT32(ubrc, IMXSerialState),
VMSTATE_UINT32(ucr3, IMXSerialState),
VMSTATE_UINT32(ucr4, IMXSerialState),
VMSTATE_END_OF_LIST()
},
};
static void imx_update(IMXSerialState *s)
{
uint32_t usr1;
uint32_t usr2;
uint32_t mask;
/*
* Lucky for us TRDY and RRDY has the same offset in both USR1 and
* UCR1, so we can get away with something as simple as the
* following:
*/
usr1 = s->usr1 & s->ucr1 & (USR1_TRDY | USR1_RRDY);
/*
* Interrupt if AGTIM is set (ageing timer interrupt in RxFIFO)
*/
usr1 |= (s->ucr2 & UCR2_ATEN) ? (s->usr1 & USR1_AGTIM) : 0;
/*
* Bits that we want in USR2 are not as conveniently laid out,
* unfortunately.
*/
mask = (s->ucr1 & UCR1_TXMPTYEN) ? USR2_TXFE : 0;
/*
* TCEN and TXDC are both bit 3
* ORE and OREN are both bit 1
* RDR and DREN are both bit 0
*/
mask |= s->ucr4 & (UCR4_WKEN | UCR4_TCEN | UCR4_DREN | UCR4_OREN);
usr2 = s->usr2 & mask;
qemu_set_irq(s->irq, usr1 || usr2);
}
static void imx_serial_rx_fifo_push(IMXSerialState *s, uint32_t value)
{
uint32_t pushed_value = value;
if (fifo32_is_full(&s->rx_fifo)) {
/* Set ORE if FIFO is already full */
s->usr2 |= USR2_ORE;
} else {
if (fifo32_num_used(&s->rx_fifo) == FIFO_SIZE - 1) {
/* Set OVRRUN on 32nd character in FIFO */
pushed_value |= URXD_ERR | URXD_OVRRUN;
}
fifo32_push(&s->rx_fifo, pushed_value);
}
}
static uint32_t imx_serial_rx_fifo_pop(IMXSerialState *s)
{
if (fifo32_is_empty(&s->rx_fifo)) {
return 0;
}
return fifo32_pop(&s->rx_fifo);
}
static void imx_serial_rx_fifo_ageing_timer_int(void *opaque)
{
IMXSerialState *s = (IMXSerialState *) opaque;
s->usr1 |= USR1_AGTIM;
imx_update(s);
}
static void imx_serial_rx_fifo_ageing_timer_restart(void *opaque)
{
/*
* Ageing timer starts ticking when
* RX FIFO is non empty and below trigger level.
* Timer is reset if new character is received or
* a FIFO read occurs.
* Timer triggers an interrupt when duration of
* 8 characters has passed (assuming 115200 baudrate).
*/
IMXSerialState *s = (IMXSerialState *) opaque;
if (!(s->usr1 & USR1_RRDY) && !(s->uts1 & UTS1_RXEMPTY)) {
timer_mod_ns(&s->ageing_timer,
qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) + AGE_DURATION_NS);
} else {
timer_del(&s->ageing_timer);
}
}
static void imx_serial_reset(IMXSerialState *s)
{
s->usr1 = USR1_TRDY | USR1_RXDS;
/*
* Fake attachment of a terminal: assert RTS.
*/
s->usr1 |= USR1_RTSS;
s->usr2 = USR2_TXFE | USR2_TXDC | USR2_DCDIN;
s->uts1 = UTS1_RXEMPTY | UTS1_TXEMPTY;
s->ucr1 = 0;
s->ucr2 = UCR2_SRST;
s->ucr3 = 0x700;
s->ubmr = 0;
s->ubrc = 4;
fifo32_reset(&s->rx_fifo);
timer_del(&s->ageing_timer);
}
static void imx_serial_reset_at_boot(DeviceState *dev)
{
IMXSerialState *s = IMX_SERIAL(dev);
imx_serial_reset(s);
/*
* enable the uart on boot, so messages from the linux decompressor
* are visible. On real hardware this is done by the boot rom
* before anything else is loaded.
*/
s->ucr1 = UCR1_UARTEN;
s->ucr2 = UCR2_TXEN;
}
static uint64_t imx_serial_read(void *opaque, hwaddr offset,
unsigned size)
{
IMXSerialState *s = (IMXSerialState *)opaque;
uint32_t c, rx_used;
uint8_t rxtl = s->ufcr & TL_MASK;
DPRINTF("read(offset=0x%" HWADDR_PRIx ")\n", offset);
switch (offset >> 2) {
case 0x0: /* URXD */
c = imx_serial_rx_fifo_pop(s);
if (!(s->uts1 & UTS1_RXEMPTY)) {
/* Character is valid */
c |= URXD_CHARRDY;
rx_used = fifo32_num_used(&s->rx_fifo);
/* Clear RRDY if below threshold */
if (rx_used < rxtl) {
s->usr1 &= ~USR1_RRDY;
}
if (rx_used == 0) {
s->usr2 &= ~USR2_RDR;
s->uts1 |= UTS1_RXEMPTY;
}
imx_update(s);
imx_serial_rx_fifo_ageing_timer_restart(s);
qemu_chr_fe_accept_input(&s->chr);
}
return c;
case 0x20: /* UCR1 */
return s->ucr1;
case 0x21: /* UCR2 */
return s->ucr2;
case 0x25: /* USR1 */
return s->usr1;
case 0x26: /* USR2 */
return s->usr2;
case 0x2A: /* BRM Modulator */
return s->ubmr;
case 0x2B: /* Baud Rate Count */
return s->ubrc;
case 0x2d: /* Test register */
return s->uts1;
case 0x24: /* UFCR */
return s->ufcr;
case 0x2c:
return s->onems;
case 0x22: /* UCR3 */
return s->ucr3;
case 0x23: /* UCR4 */
return s->ucr4;
case 0x29: /* BRM Incremental */
return 0x0; /* TODO */
default:
qemu_log_mask(LOG_GUEST_ERROR, "[%s]%s: Bad register at offset 0x%"
HWADDR_PRIx "\n", TYPE_IMX_SERIAL, __func__, offset);
return 0;
}
}
static void imx_serial_write(void *opaque, hwaddr offset,
uint64_t value, unsigned size)
{
IMXSerialState *s = (IMXSerialState *)opaque;
Chardev *chr = qemu_chr_fe_get_driver(&s->chr);
unsigned char ch;
DPRINTF("write(offset=0x%" HWADDR_PRIx ", value = 0x%x) to %s\n",
offset, (unsigned int)value, chr ? chr->label : "NODEV");
switch (offset >> 2) {
case 0x10: /* UTXD */
ch = value;
if (s->ucr2 & UCR2_TXEN) {
/* XXX this blocks entire thread. Rewrite to use
* qemu_chr_fe_write and background I/O callbacks */
qemu_chr_fe_write_all(&s->chr, &ch, 1);
s->usr1 &= ~USR1_TRDY;
s->usr2 &= ~USR2_TXDC;
imx_update(s);
s->usr1 |= USR1_TRDY;
s->usr2 |= USR2_TXDC;
imx_update(s);
}
break;
case 0x20: /* UCR1 */
s->ucr1 = value & 0xffff;
DPRINTF("write(ucr1=%x)\n", (unsigned int)value);
imx_update(s);
break;
case 0x21: /* UCR2 */
/*
* Only a few bits in control register 2 are implemented as yet.
* If it's intended to use a real serial device as a back-end, this
* register will have to be implemented more fully.
*/
if (!(value & UCR2_SRST)) {
imx_serial_reset(s);
imx_update(s);
value |= UCR2_SRST;
}
if (value & UCR2_RXEN) {
if (!(s->ucr2 & UCR2_RXEN)) {
qemu_chr_fe_accept_input(&s->chr);
}
}
s->ucr2 = value & 0xffff;
break;
case 0x25: /* USR1 */
value &= USR1_AWAKE | USR1_AIRINT | USR1_DTRD | USR1_AGTIM |
USR1_FRAMERR | USR1_ESCF | USR1_RTSD | USR1_PARTYER;
s->usr1 &= ~value;
break;
case 0x26: /* USR2 */
/*
* Writing 1 to some bits clears them; all other
* values are ignored
*/
value &= USR2_ADET | USR2_DTRF | USR2_IDLE | USR2_ACST |
USR2_RIDELT | USR2_IRINT | USR2_WAKE |
USR2_DCDDELT | USR2_RTSF | USR2_BRCD | USR2_ORE;
s->usr2 &= ~value;
break;
/*
* Linux expects to see what it writes to these registers
* We don't currently alter the baud rate
*/
case 0x29: /* UBIR */
s->ubrc = value & 0xffff;
break;
case 0x2a: /* UBMR */
s->ubmr = value & 0xffff;
break;
case 0x2c: /* One ms reg */
s->onems = value & 0xffff;
break;
case 0x24: /* FIFO control register */
s->ufcr = value & 0xffff;
break;
case 0x22: /* UCR3 */
s->ucr3 = value & 0xffff;
break;
case 0x23: /* UCR4 */
s->ucr4 = value & 0xffff;
imx_update(s);
break;
case 0x2d: /* UTS1 */
qemu_log_mask(LOG_UNIMP, "[%s]%s: Unimplemented reg 0x%"
HWADDR_PRIx "\n", TYPE_IMX_SERIAL, __func__, offset);
/* TODO */
break;
default:
qemu_log_mask(LOG_GUEST_ERROR, "[%s]%s: Bad register at offset 0x%"
HWADDR_PRIx "\n", TYPE_IMX_SERIAL, __func__, offset);
}
}
static int imx_can_receive(void *opaque)
{
IMXSerialState *s = (IMXSerialState *)opaque;
return s->ucr2 & UCR2_RXEN && fifo32_num_used(&s->rx_fifo) < FIFO_SIZE;
}
static void imx_put_data(void *opaque, uint32_t value)
{
IMXSerialState *s = (IMXSerialState *)opaque;
uint8_t rxtl = s->ufcr & TL_MASK;
DPRINTF("received char\n");
imx_serial_rx_fifo_push(s, value);
if (fifo32_num_used(&s->rx_fifo) >= rxtl) {
s->usr1 |= USR1_RRDY;
}
imx_serial_rx_fifo_ageing_timer_restart(s);
s->usr2 |= USR2_RDR;
s->uts1 &= ~UTS1_RXEMPTY;
if (value & URXD_BRK) {
s->usr2 |= USR2_BRCD;
}
imx_update(s);
}
static void imx_receive(void *opaque, const uint8_t *buf, int size)
{
IMXSerialState *s = (IMXSerialState *)opaque;
s->usr2 |= USR2_WAKE;
imx_put_data(opaque, *buf);
}
static void imx_event(void *opaque, QEMUChrEvent event)
{
if (event == CHR_EVENT_BREAK) {
imx_put_data(opaque, URXD_BRK | URXD_FRMERR | URXD_ERR);
}
}
static const struct MemoryRegionOps imx_serial_ops = {
.read = imx_serial_read,
.write = imx_serial_write,
.endianness = DEVICE_NATIVE_ENDIAN,
};
static void imx_serial_realize(DeviceState *dev, Error **errp)
{
IMXSerialState *s = IMX_SERIAL(dev);
fifo32_create(&s->rx_fifo, FIFO_SIZE);
timer_init_ns(&s->ageing_timer, QEMU_CLOCK_VIRTUAL,
imx_serial_rx_fifo_ageing_timer_int, s);
DPRINTF("char dev for uart: %p\n", qemu_chr_fe_get_driver(&s->chr));
qemu_chr_fe_set_handlers(&s->chr, imx_can_receive, imx_receive,
imx_event, NULL, s, NULL, true);
}
static void imx_serial_init(Object *obj)
{
SysBusDevice *sbd = SYS_BUS_DEVICE(obj);
IMXSerialState *s = IMX_SERIAL(obj);
memory_region_init_io(&s->iomem, obj, &imx_serial_ops, s,
TYPE_IMX_SERIAL, 0x1000);
sysbus_init_mmio(sbd, &s->iomem);
sysbus_init_irq(sbd, &s->irq);
}
static Property imx_serial_properties[] = {
DEFINE_PROP_CHR("chardev", IMXSerialState, chr),
DEFINE_PROP_END_OF_LIST(),
};
static void imx_serial_class_init(ObjectClass *klass, void *data)
{
DeviceClass *dc = DEVICE_CLASS(klass);
dc->realize = imx_serial_realize;
dc->vmsd = &vmstate_imx_serial;
dc->reset = imx_serial_reset_at_boot;
set_bit(DEVICE_CATEGORY_INPUT, dc->categories);
dc->desc = "i.MX series UART";
device_class_set_props(dc, imx_serial_properties);
}
static const TypeInfo imx_serial_info = {
.name = TYPE_IMX_SERIAL,
.parent = TYPE_SYS_BUS_DEVICE,
.instance_size = sizeof(IMXSerialState),
.instance_init = imx_serial_init,
.class_init = imx_serial_class_init,
};
static void imx_serial_register_types(void)
{
type_register_static(&imx_serial_info);
}
type_init(imx_serial_register_types)
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