freebsd-dev/sys/dev/uart/uart_dev_sab82532.c
Marcel Moolenaar f8100ce2a7 Don't expose the uart_ops structure directly, but instead have
it obtained through the uart_class structure. This allows us
to declare the uart_class structure as weak and as such allows
us to reference it even when it's not compiled-in.
It also allows is to get the uart_ops structure by name, which
makes it possible to implement the dt tag handling in uart_getenv().
The side-effect of all this is that we're using the uart_class
structure more consistently which means that we now also have
access to the size of the bus space block needed by the hardware
when we map the bus space, eliminating any hardcoding.
2007-04-02 22:00:22 +00:00

727 lines
17 KiB
C

/*-
* Copyright (c) 2003 Marcel Moolenaar
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/bus.h>
#include <sys/conf.h>
#include <machine/bus.h>
#include <dev/uart/uart.h>
#include <dev/uart/uart_cpu.h>
#include <dev/uart/uart_bus.h>
#include <dev/ic/sab82532.h>
#include "uart_if.h"
#define DEFAULT_RCLK 29491200
/*
* NOTE: To allow us to read the baudrate divisor from the chip, we
* copy the value written to the write-only BGR register to an unused
* read-write register. We use TCR for that.
*/
static int
sab82532_delay(struct uart_bas *bas)
{
int divisor, m, n;
uint8_t bgr, ccr2;
bgr = uart_getreg(bas, SAB_TCR);
ccr2 = uart_getreg(bas, SAB_CCR2);
n = (bgr & 0x3f) + 1;
m = (bgr >> 6) | ((ccr2 >> 4) & 0xC);
divisor = n * (1<<m);
/* 1/10th the time to transmit 1 character (estimate). */
return (16000000 * divisor / bas->rclk);
}
static int
sab82532_divisor(int rclk, int baudrate)
{
int act_baud, act_div, divisor;
int error, m, n;
if (baudrate == 0)
return (0);
divisor = (rclk / (baudrate << 3) + 1) >> 1;
if (divisor < 2 || divisor >= 1048576)
return (0);
/* Find the best (N+1,M) pair. */
for (m = 1; m < 15; m++) {
n = divisor / (1<<m);
if (n < 1 || n > 63)
continue;
act_div = n * (1<<m);
act_baud = rclk / (act_div << 4);
/* 10 times error in percent: */
error = ((act_baud - baudrate) * 2000 / baudrate + 1) >> 1;
/* 3.0% maximum error tolerance: */
if (error < -30 || error > 30)
continue;
/* Got it. */
return ((n - 1) | (m << 6));
}
return (0);
}
static void
sab82532_flush(struct uart_bas *bas, int what)
{
if (what & UART_FLUSH_TRANSMITTER) {
while (uart_getreg(bas, SAB_STAR) & SAB_STAR_CEC)
;
uart_setreg(bas, SAB_CMDR, SAB_CMDR_XRES);
uart_barrier(bas);
}
if (what & UART_FLUSH_RECEIVER) {
while (uart_getreg(bas, SAB_STAR) & SAB_STAR_CEC)
;
uart_setreg(bas, SAB_CMDR, SAB_CMDR_RRES);
uart_barrier(bas);
}
}
static int
sab82532_param(struct uart_bas *bas, int baudrate, int databits, int stopbits,
int parity)
{
int divisor;
uint8_t ccr2, dafo;
if (databits >= 8)
dafo = SAB_DAFO_CHL_CS8;
else if (databits == 7)
dafo = SAB_DAFO_CHL_CS7;
else if (databits == 6)
dafo = SAB_DAFO_CHL_CS6;
else
dafo = SAB_DAFO_CHL_CS5;
if (stopbits > 1)
dafo |= SAB_DAFO_STOP;
switch (parity) {
case UART_PARITY_EVEN: dafo |= SAB_DAFO_PAR_EVEN; break;
case UART_PARITY_MARK: dafo |= SAB_DAFO_PAR_MARK; break;
case UART_PARITY_NONE: dafo |= SAB_DAFO_PAR_NONE; break;
case UART_PARITY_ODD: dafo |= SAB_DAFO_PAR_ODD; break;
case UART_PARITY_SPACE: dafo |= SAB_DAFO_PAR_SPACE; break;
default: return (EINVAL);
}
/* Set baudrate. */
if (baudrate > 0) {
divisor = sab82532_divisor(bas->rclk, baudrate);
if (divisor == 0)
return (EINVAL);
uart_setreg(bas, SAB_BGR, divisor & 0xff);
uart_barrier(bas);
/* Allow reading the (n-1,m) tuple from the chip. */
uart_setreg(bas, SAB_TCR, divisor & 0xff);
uart_barrier(bas);
ccr2 = uart_getreg(bas, SAB_CCR2);
ccr2 &= ~(SAB_CCR2_BR9 | SAB_CCR2_BR8);
ccr2 |= (divisor >> 2) & (SAB_CCR2_BR9 | SAB_CCR2_BR8);
uart_setreg(bas, SAB_CCR2, ccr2);
uart_barrier(bas);
}
uart_setreg(bas, SAB_DAFO, dafo);
uart_barrier(bas);
return (0);
}
/*
* Low-level UART interface.
*/
static int sab82532_probe(struct uart_bas *bas);
static void sab82532_init(struct uart_bas *bas, int, int, int, int);
static void sab82532_term(struct uart_bas *bas);
static void sab82532_putc(struct uart_bas *bas, int);
static int sab82532_rxready(struct uart_bas *bas);
static int sab82532_getc(struct uart_bas *bas, struct mtx *);
static struct uart_ops uart_sab82532_ops = {
.probe = sab82532_probe,
.init = sab82532_init,
.term = sab82532_term,
.putc = sab82532_putc,
.rxready = sab82532_rxready,
.getc = sab82532_getc,
};
static int
sab82532_probe(struct uart_bas *bas)
{
return (0);
}
static void
sab82532_init(struct uart_bas *bas, int baudrate, int databits, int stopbits,
int parity)
{
uint8_t ccr0, pvr;
if (bas->rclk == 0)
bas->rclk = DEFAULT_RCLK;
/*
* Set all pins, except the DTR pins (pin 1 and 2) to be inputs.
* Pin 4 is magical, meaning that I don't know what it does, but
* it too has to be set to output.
*/
uart_setreg(bas, SAB_PCR,
~(SAB_PVR_DTR_A|SAB_PVR_DTR_B|SAB_PVR_MAGIC));
uart_barrier(bas);
/* Disable port interrupts. */
uart_setreg(bas, SAB_PIM, 0xff);
uart_barrier(bas);
/* Interrupts are active low. */
uart_setreg(bas, SAB_IPC, SAB_IPC_ICPL);
uart_barrier(bas);
/* Set DTR. */
pvr = uart_getreg(bas, SAB_PVR);
switch (bas->chan) {
case 1:
pvr &= ~SAB_PVR_DTR_A;
break;
case 2:
pvr &= ~SAB_PVR_DTR_B;
break;
}
uart_setreg(bas, SAB_PVR, pvr | SAB_PVR_MAGIC);
uart_barrier(bas);
/* power down */
uart_setreg(bas, SAB_CCR0, 0);
uart_barrier(bas);
/* set basic configuration */
ccr0 = SAB_CCR0_MCE|SAB_CCR0_SC_NRZ|SAB_CCR0_SM_ASYNC;
uart_setreg(bas, SAB_CCR0, ccr0);
uart_barrier(bas);
uart_setreg(bas, SAB_CCR1, SAB_CCR1_ODS|SAB_CCR1_BCR|SAB_CCR1_CM_7);
uart_barrier(bas);
uart_setreg(bas, SAB_CCR2, SAB_CCR2_BDF|SAB_CCR2_SSEL|SAB_CCR2_TOE);
uart_barrier(bas);
uart_setreg(bas, SAB_CCR3, 0);
uart_barrier(bas);
uart_setreg(bas, SAB_CCR4, SAB_CCR4_MCK4|SAB_CCR4_EBRG|SAB_CCR4_ICD);
uart_barrier(bas);
uart_setreg(bas, SAB_MODE, SAB_MODE_FCTS|SAB_MODE_RTS|SAB_MODE_RAC);
uart_barrier(bas);
uart_setreg(bas, SAB_RFC, SAB_RFC_DPS|SAB_RFC_RFDF|
SAB_RFC_RFTH_32CHAR);
uart_barrier(bas);
sab82532_param(bas, baudrate, databits, stopbits, parity);
/* Clear interrupts. */
uart_setreg(bas, SAB_IMR0, (unsigned char)~SAB_IMR0_TCD);
uart_setreg(bas, SAB_IMR1, 0xff);
uart_barrier(bas);
uart_getreg(bas, SAB_ISR0);
uart_getreg(bas, SAB_ISR1);
uart_barrier(bas);
sab82532_flush(bas, UART_FLUSH_TRANSMITTER|UART_FLUSH_RECEIVER);
/* Power up. */
uart_setreg(bas, SAB_CCR0, ccr0|SAB_CCR0_PU);
uart_barrier(bas);
}
static void
sab82532_term(struct uart_bas *bas)
{
uint8_t pvr;
pvr = uart_getreg(bas, SAB_PVR);
switch (bas->chan) {
case 1:
pvr |= SAB_PVR_DTR_A;
break;
case 2:
pvr |= SAB_PVR_DTR_B;
break;
}
uart_setreg(bas, SAB_PVR, pvr);
uart_barrier(bas);
}
static void
sab82532_putc(struct uart_bas *bas, int c)
{
int delay, limit;
/* 1/10th the time to transmit 1 character (estimate). */
delay = sab82532_delay(bas);
limit = 20;
while ((uart_getreg(bas, SAB_STAR) & SAB_STAR_TEC) && --limit)
DELAY(delay);
uart_setreg(bas, SAB_TIC, c);
limit = 20;
while ((uart_getreg(bas, SAB_STAR) & SAB_STAR_TEC) && --limit)
DELAY(delay);
}
static int
sab82532_rxready(struct uart_bas *bas)
{
return ((uart_getreg(bas, SAB_STAR) & SAB_STAR_RFNE) != 0 ? 1 : 0);
}
static int
sab82532_getc(struct uart_bas *bas, struct mtx *hwmtx)
{
int c, delay;
uart_lock(hwmtx);
/* 1/10th the time to transmit 1 character (estimate). */
delay = sab82532_delay(bas);
while (!(uart_getreg(bas, SAB_STAR) & SAB_STAR_RFNE)) {
uart_unlock(hwmtx);
DELAY(delay);
uart_lock(hwmtx);
}
while (uart_getreg(bas, SAB_STAR) & SAB_STAR_CEC)
;
uart_setreg(bas, SAB_CMDR, SAB_CMDR_RFRD);
uart_barrier(bas);
while (!(uart_getreg(bas, SAB_ISR0) & SAB_ISR0_TCD))
DELAY(delay);
c = uart_getreg(bas, SAB_RFIFO);
uart_barrier(bas);
/* Blow away everything left in the FIFO... */
while (uart_getreg(bas, SAB_STAR) & SAB_STAR_CEC)
;
uart_setreg(bas, SAB_CMDR, SAB_CMDR_RMC);
uart_barrier(bas);
uart_unlock(hwmtx);
return (c);
}
/*
* High-level UART interface.
*/
struct sab82532_softc {
struct uart_softc base;
};
static int sab82532_bus_attach(struct uart_softc *);
static int sab82532_bus_detach(struct uart_softc *);
static int sab82532_bus_flush(struct uart_softc *, int);
static int sab82532_bus_getsig(struct uart_softc *);
static int sab82532_bus_ioctl(struct uart_softc *, int, intptr_t);
static int sab82532_bus_ipend(struct uart_softc *);
static int sab82532_bus_param(struct uart_softc *, int, int, int, int);
static int sab82532_bus_probe(struct uart_softc *);
static int sab82532_bus_receive(struct uart_softc *);
static int sab82532_bus_setsig(struct uart_softc *, int);
static int sab82532_bus_transmit(struct uart_softc *);
static kobj_method_t sab82532_methods[] = {
KOBJMETHOD(uart_attach, sab82532_bus_attach),
KOBJMETHOD(uart_detach, sab82532_bus_detach),
KOBJMETHOD(uart_flush, sab82532_bus_flush),
KOBJMETHOD(uart_getsig, sab82532_bus_getsig),
KOBJMETHOD(uart_ioctl, sab82532_bus_ioctl),
KOBJMETHOD(uart_ipend, sab82532_bus_ipend),
KOBJMETHOD(uart_param, sab82532_bus_param),
KOBJMETHOD(uart_probe, sab82532_bus_probe),
KOBJMETHOD(uart_receive, sab82532_bus_receive),
KOBJMETHOD(uart_setsig, sab82532_bus_setsig),
KOBJMETHOD(uart_transmit, sab82532_bus_transmit),
{ 0, 0 }
};
struct uart_class uart_sab82532_class = {
"sab82532",
sab82532_methods,
sizeof(struct sab82532_softc),
.uc_ops = &uart_sab82532_ops,
.uc_range = 64,
.uc_rclk = DEFAULT_RCLK
};
#define SIGCHG(c, i, s, d) \
if (c) { \
i |= (i & s) ? s : s | d; \
} else { \
i = (i & s) ? (i & ~s) | d : i; \
}
static int
sab82532_bus_attach(struct uart_softc *sc)
{
struct uart_bas *bas;
uint8_t imr0, imr1;
bas = &sc->sc_bas;
if (sc->sc_sysdev == NULL)
sab82532_init(bas, 9600, 8, 1, UART_PARITY_NONE);
sc->sc_rxfifosz = 32;
sc->sc_txfifosz = 32;
imr0 = SAB_IMR0_TCD|SAB_IMR0_TIME|SAB_IMR0_CDSC|SAB_IMR0_RFO|
SAB_IMR0_RPF;
uart_setreg(bas, SAB_IMR0, 0xff & ~imr0);
imr1 = SAB_IMR1_BRKT|SAB_IMR1_ALLS|SAB_IMR1_CSC;
uart_setreg(bas, SAB_IMR1, 0xff & ~imr1);
uart_barrier(bas);
if (sc->sc_sysdev == NULL)
sab82532_bus_setsig(sc, SER_DDTR|SER_DRTS);
(void)sab82532_bus_getsig(sc);
return (0);
}
static int
sab82532_bus_detach(struct uart_softc *sc)
{
struct uart_bas *bas;
bas = &sc->sc_bas;
uart_setreg(bas, SAB_IMR0, 0xff);
uart_setreg(bas, SAB_IMR1, 0xff);
uart_barrier(bas);
uart_getreg(bas, SAB_ISR0);
uart_getreg(bas, SAB_ISR1);
uart_barrier(bas);
uart_setreg(bas, SAB_CCR0, 0);
uart_barrier(bas);
return (0);
}
static int
sab82532_bus_flush(struct uart_softc *sc, int what)
{
uart_lock(sc->sc_hwmtx);
sab82532_flush(&sc->sc_bas, what);
uart_unlock(sc->sc_hwmtx);
return (0);
}
static int
sab82532_bus_getsig(struct uart_softc *sc)
{
struct uart_bas *bas;
uint32_t new, old, sig;
uint8_t pvr, star, vstr;
bas = &sc->sc_bas;
do {
old = sc->sc_hwsig;
sig = old;
uart_lock(sc->sc_hwmtx);
star = uart_getreg(bas, SAB_STAR);
SIGCHG(star & SAB_STAR_CTS, sig, SER_CTS, SER_DCTS);
vstr = uart_getreg(bas, SAB_VSTR);
SIGCHG(vstr & SAB_VSTR_CD, sig, SER_DCD, SER_DDCD);
pvr = ~uart_getreg(bas, SAB_PVR);
switch (bas->chan) {
case 1:
pvr &= SAB_PVR_DSR_A;
break;
case 2:
pvr &= SAB_PVR_DSR_B;
break;
}
SIGCHG(pvr, sig, SER_DSR, SER_DDSR);
uart_unlock(sc->sc_hwmtx);
new = sig & ~SER_MASK_DELTA;
} while (!atomic_cmpset_32(&sc->sc_hwsig, old, new));
return (sig);
}
static int
sab82532_bus_ioctl(struct uart_softc *sc, int request, intptr_t data)
{
struct uart_bas *bas;
uint8_t dafo, mode;
int error;
bas = &sc->sc_bas;
error = 0;
uart_lock(sc->sc_hwmtx);
switch (request) {
case UART_IOCTL_BREAK:
dafo = uart_getreg(bas, SAB_DAFO);
if (data)
dafo |= SAB_DAFO_XBRK;
else
dafo &= ~SAB_DAFO_XBRK;
uart_setreg(bas, SAB_DAFO, dafo);
uart_barrier(bas);
break;
case UART_IOCTL_IFLOW:
mode = uart_getreg(bas, SAB_MODE);
if (data) {
mode &= ~SAB_MODE_RTS;
mode |= SAB_MODE_FRTS;
} else {
mode |= SAB_MODE_RTS;
mode &= ~SAB_MODE_FRTS;
}
uart_setreg(bas, SAB_MODE, mode);
uart_barrier(bas);
break;
case UART_IOCTL_OFLOW:
mode = uart_getreg(bas, SAB_MODE);
if (data)
mode &= ~SAB_MODE_FCTS;
else
mode |= SAB_MODE_FCTS;
uart_setreg(bas, SAB_MODE, mode);
uart_barrier(bas);
break;
default:
error = EINVAL;
break;
}
uart_unlock(sc->sc_hwmtx);
return (error);
}
static int
sab82532_bus_ipend(struct uart_softc *sc)
{
struct uart_bas *bas;
int ipend;
uint8_t isr0, isr1;
bas = &sc->sc_bas;
uart_lock(sc->sc_hwmtx);
isr0 = uart_getreg(bas, SAB_ISR0);
isr1 = uart_getreg(bas, SAB_ISR1);
uart_barrier(bas);
if (isr0 & SAB_ISR0_TIME) {
while (uart_getreg(bas, SAB_STAR) & SAB_STAR_CEC)
;
uart_setreg(bas, SAB_CMDR, SAB_CMDR_RFRD);
uart_barrier(bas);
}
uart_unlock(sc->sc_hwmtx);
ipend = 0;
if (isr1 & SAB_ISR1_BRKT)
ipend |= SER_INT_BREAK;
if (isr0 & SAB_ISR0_RFO)
ipend |= SER_INT_OVERRUN;
if (isr0 & (SAB_ISR0_TCD|SAB_ISR0_RPF))
ipend |= SER_INT_RXREADY;
if ((isr0 & SAB_ISR0_CDSC) || (isr1 & SAB_ISR1_CSC))
ipend |= SER_INT_SIGCHG;
if (isr1 & SAB_ISR1_ALLS)
ipend |= SER_INT_TXIDLE;
return (ipend);
}
static int
sab82532_bus_param(struct uart_softc *sc, int baudrate, int databits,
int stopbits, int parity)
{
struct uart_bas *bas;
int error;
bas = &sc->sc_bas;
uart_lock(sc->sc_hwmtx);
error = sab82532_param(bas, baudrate, databits, stopbits, parity);
uart_unlock(sc->sc_hwmtx);
return (error);
}
static int
sab82532_bus_probe(struct uart_softc *sc)
{
char buf[80];
const char *vstr;
int error;
char ch;
error = sab82532_probe(&sc->sc_bas);
if (error)
return (error);
ch = sc->sc_bas.chan - 1 + 'A';
switch (uart_getreg(&sc->sc_bas, SAB_VSTR) & SAB_VSTR_VMASK) {
case SAB_VSTR_V_1:
vstr = "v1";
break;
case SAB_VSTR_V_2:
vstr = "v2";
break;
case SAB_VSTR_V_32:
vstr = "v3.2";
sc->sc_hwiflow = 0; /* CTS doesn't work with RFC:RFDF. */
sc->sc_hwoflow = 1;
break;
default:
vstr = "v4?";
break;
}
snprintf(buf, sizeof(buf), "SAB 82532 %s, channel %c", vstr, ch);
device_set_desc_copy(sc->sc_dev, buf);
return (0);
}
static int
sab82532_bus_receive(struct uart_softc *sc)
{
struct uart_bas *bas;
int i, rbcl, xc;
uint8_t s;
bas = &sc->sc_bas;
uart_lock(sc->sc_hwmtx);
if (uart_getreg(bas, SAB_STAR) & SAB_STAR_RFNE) {
rbcl = uart_getreg(bas, SAB_RBCL) & 31;
if (rbcl == 0)
rbcl = 32;
for (i = 0; i < rbcl; i += 2) {
if (uart_rx_full(sc)) {
sc->sc_rxbuf[sc->sc_rxput] = UART_STAT_OVERRUN;
break;
}
xc = uart_getreg(bas, SAB_RFIFO);
s = uart_getreg(bas, SAB_RFIFO + 1);
if (s & SAB_RSTAT_FE)
xc |= UART_STAT_FRAMERR;
if (s & SAB_RSTAT_PE)
xc |= UART_STAT_PARERR;
uart_rx_put(sc, xc);
}
}
while (uart_getreg(bas, SAB_STAR) & SAB_STAR_CEC)
;
uart_setreg(bas, SAB_CMDR, SAB_CMDR_RMC);
uart_barrier(bas);
uart_unlock(sc->sc_hwmtx);
return (0);
}
static int
sab82532_bus_setsig(struct uart_softc *sc, int sig)
{
struct uart_bas *bas;
uint32_t new, old;
uint8_t mode, pvr;
bas = &sc->sc_bas;
do {
old = sc->sc_hwsig;
new = old;
if (sig & SER_DDTR) {
SIGCHG(sig & SER_DTR, new, SER_DTR,
SER_DDTR);
}
if (sig & SER_DRTS) {
SIGCHG(sig & SER_RTS, new, SER_RTS,
SER_DRTS);
}
} while (!atomic_cmpset_32(&sc->sc_hwsig, old, new));
uart_lock(sc->sc_hwmtx);
/* Set DTR pin. */
pvr = uart_getreg(bas, SAB_PVR);
switch (bas->chan) {
case 1:
if (new & SER_DTR)
pvr &= ~SAB_PVR_DTR_A;
else
pvr |= SAB_PVR_DTR_A;
break;
case 2:
if (new & SER_DTR)
pvr &= ~SAB_PVR_DTR_B;
else
pvr |= SAB_PVR_DTR_B;
break;
}
uart_setreg(bas, SAB_PVR, pvr);
/* Set RTS pin. */
mode = uart_getreg(bas, SAB_MODE);
if (new & SER_RTS)
mode &= ~SAB_MODE_FRTS;
else
mode |= SAB_MODE_FRTS;
uart_setreg(bas, SAB_MODE, mode);
uart_barrier(bas);
uart_unlock(sc->sc_hwmtx);
return (0);
}
static int
sab82532_bus_transmit(struct uart_softc *sc)
{
struct uart_bas *bas;
int i;
bas = &sc->sc_bas;
uart_lock(sc->sc_hwmtx);
while (!(uart_getreg(bas, SAB_STAR) & SAB_STAR_XFW))
;
for (i = 0; i < sc->sc_txdatasz; i++)
uart_setreg(bas, SAB_XFIFO + i, sc->sc_txbuf[i]);
uart_barrier(bas);
while (uart_getreg(bas, SAB_STAR) & SAB_STAR_CEC)
;
uart_setreg(bas, SAB_CMDR, SAB_CMDR_XF);
sc->sc_txbusy = 1;
uart_unlock(sc->sc_hwmtx);
return (0);
}