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[SUNSAB]: Defer register updates until transmitter is idle.
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The chip can emit garbage characters if we touch the
settings while characters are going out.

Signed-off-by: David S. Miller <davem@davemloft.net>
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David S. Miller committed May 11, 2005
1 parent 88d7bd8 commit e4fdee8
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Showing 2 changed files with 72 additions and 38 deletions.
109 changes: 71 additions & 38 deletions drivers/serial/sunsab.c
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Original file line number Diff line number Diff line change
Expand Up @@ -61,6 +61,16 @@ struct uart_sunsab_port {
unsigned char pvr_dtr_bit; /* Which PVR bit is DTR */
unsigned char pvr_dsr_bit; /* Which PVR bit is DSR */
int type; /* SAB82532 version */

/* Setting configuration bits while the transmitter is active
* can cause garbage characters to get emitted by the chip.
* Therefore, we cache such writes here and do the real register
* write the next time the transmitter becomes idle.
*/
unsigned int cached_ebrg;
unsigned char cached_mode;
unsigned char cached_pvr;
unsigned char cached_dafo;
};

/*
Expand Down Expand Up @@ -236,6 +246,7 @@ receive_chars(struct uart_sunsab_port *up,
}

static void sunsab_stop_tx(struct uart_port *, unsigned int);
static void sunsab_tx_idle(struct uart_sunsab_port *);

static void transmit_chars(struct uart_sunsab_port *up,
union sab82532_irq_status *stat)
Expand All @@ -258,6 +269,7 @@ static void transmit_chars(struct uart_sunsab_port *up,
return;

set_bit(SAB82532_XPR, &up->irqflags);
sunsab_tx_idle(up);

if (uart_circ_empty(xmit) || uart_tx_stopped(&up->port)) {
up->interrupt_mask1 |= SAB82532_IMR1_XPR;
Expand Down Expand Up @@ -397,21 +409,21 @@ static void sunsab_set_mctrl(struct uart_port *port, unsigned int mctrl)
struct uart_sunsab_port *up = (struct uart_sunsab_port *) port;

if (mctrl & TIOCM_RTS) {
writeb(readb(&up->regs->rw.mode) & ~SAB82532_MODE_FRTS,
&up->regs->rw.mode);
writeb(readb(&up->regs->rw.mode) | SAB82532_MODE_RTS,
&up->regs->rw.mode);
up->cached_mode &= ~SAB82532_MODE_FRTS;
up->cached_mode |= SAB82532_MODE_RTS;
} else {
writeb(readb(&up->regs->rw.mode) | SAB82532_MODE_FRTS,
&up->regs->rw.mode);
writeb(readb(&up->regs->rw.mode) | SAB82532_MODE_RTS,
&up->regs->rw.mode);
up->cached_mode |= (SAB82532_MODE_FRTS |
SAB82532_MODE_RTS);
}
if (mctrl & TIOCM_DTR) {
writeb(readb(&up->regs->rw.pvr) & ~(up->pvr_dtr_bit), &up->regs->rw.pvr);
up->cached_pvr &= ~(up->pvr_dtr_bit);
} else {
writeb(readb(&up->regs->rw.pvr) | up->pvr_dtr_bit, &up->regs->rw.pvr);
up->cached_pvr |= up->pvr_dtr_bit;
}

set_bit(SAB82532_REGS_PENDING, &up->irqflags);
if (test_bit(SAB82532_XPR, &up->irqflags))
sunsab_tx_idle(up);
}

/* port->lock is not held. */
Expand Down Expand Up @@ -449,6 +461,25 @@ static void sunsab_stop_tx(struct uart_port *port, unsigned int tty_stop)
writeb(up->interrupt_mask1, &up->regs->w.imr1);
}

/* port->lock held by caller. */
static void sunsab_tx_idle(struct uart_sunsab_port *up)
{
if (test_bit(SAB82532_REGS_PENDING, &up->irqflags)) {
u8 tmp;

clear_bit(SAB82532_REGS_PENDING, &up->irqflags);
writeb(up->cached_mode, &up->regs->rw.mode);
writeb(up->cached_pvr, &up->regs->rw.pvr);
writeb(up->cached_dafo, &up->regs->w.dafo);

writeb(up->cached_ebrg & 0xff, &up->regs->w.bgr);
tmp = readb(&up->regs->rw.ccr2);
tmp &= ~0xc0;
tmp |= (up->cached_ebrg >> 2) & 0xc0;
writeb(tmp, &up->regs->rw.ccr2);
}
}

/* port->lock held by caller. */
static void sunsab_start_tx(struct uart_port *port, unsigned int tty_start)
{
Expand Down Expand Up @@ -517,12 +548,16 @@ static void sunsab_break_ctl(struct uart_port *port, int break_state)

spin_lock_irqsave(&up->port.lock, flags);

val = readb(&up->regs->rw.dafo);
val = up->cached_dafo;
if (break_state)
val |= SAB82532_DAFO_XBRK;
else
val &= ~SAB82532_DAFO_XBRK;
writeb(val, &up->regs->rw.dafo);
up->cached_dafo = val;

set_bit(SAB82532_REGS_PENDING, &up->irqflags);
if (test_bit(SAB82532_XPR, &up->irqflags))
sunsab_tx_idle(up);

spin_unlock_irqrestore(&up->port.lock, flags);
}
Expand Down Expand Up @@ -566,8 +601,9 @@ static int sunsab_startup(struct uart_port *port)
SAB82532_CCR2_TOE, &up->regs->w.ccr2);
writeb(0, &up->regs->w.ccr3);
writeb(SAB82532_CCR4_MCK4 | SAB82532_CCR4_EBRG, &up->regs->w.ccr4);
writeb(SAB82532_MODE_RTS | SAB82532_MODE_FCTS |
SAB82532_MODE_RAC, &up->regs->w.mode);
up->cached_mode = (SAB82532_MODE_RTS | SAB82532_MODE_FCTS |
SAB82532_MODE_RAC);
writeb(up->cached_mode, &up->regs->w.mode);
writeb(SAB82532_RFC_DPS|SAB82532_RFC_RFTH_32, &up->regs->w.rfc);

tmp = readb(&up->regs->rw.ccr0);
Expand Down Expand Up @@ -598,7 +634,6 @@ static void sunsab_shutdown(struct uart_port *port)
{
struct uart_sunsab_port *up = (struct uart_sunsab_port *) port;
unsigned long flags;
unsigned char tmp;

spin_lock_irqsave(&up->port.lock, flags);

Expand All @@ -609,14 +644,13 @@ static void sunsab_shutdown(struct uart_port *port)
writeb(up->interrupt_mask1, &up->regs->w.imr1);

/* Disable break condition */
tmp = readb(&up->regs->rw.dafo);
tmp &= ~SAB82532_DAFO_XBRK;
writeb(tmp, &up->regs->rw.dafo);
up->cached_dafo = readb(&up->regs->rw.dafo);
up->cached_dafo &= ~SAB82532_DAFO_XBRK;
writeb(up->cached_dafo, &up->regs->rw.dafo);

/* Disable Receiver */
tmp = readb(&up->regs->rw.mode);
tmp &= ~SAB82532_MODE_RAC;
writeb(tmp, &up->regs->rw.mode);
up->cached_mode &= ~SAB82532_MODE_RAC;
writeb(up->cached_mode, &up->regs->rw.mode);

/*
* XXX FIXME
Expand Down Expand Up @@ -685,7 +719,6 @@ static void sunsab_convert_to_sab(struct uart_sunsab_port *up, unsigned int cfla
unsigned int iflag, unsigned int baud,
unsigned int quot)
{
unsigned int ebrg;
unsigned char dafo;
int bits, n, m;

Expand Down Expand Up @@ -714,10 +747,11 @@ static void sunsab_convert_to_sab(struct uart_sunsab_port *up, unsigned int cfla
} else {
dafo |= SAB82532_DAFO_PAR_EVEN;
}
up->cached_dafo = dafo;

calc_ebrg(baud, &n, &m);

ebrg = n | (m << 6);
up->cached_ebrg = n | (m << 6);

up->tec_timeout = (10 * 1000000) / baud;
up->cec_timeout = up->tec_timeout >> 2;
Expand Down Expand Up @@ -770,16 +804,13 @@ static void sunsab_convert_to_sab(struct uart_sunsab_port *up, unsigned int cfla
uart_update_timeout(&up->port, cflag,
(up->port.uartclk / (16 * quot)));

/* Now bang the new settings into the chip. */
sunsab_cec_wait(up);
sunsab_tec_wait(up);
writeb(dafo, &up->regs->w.dafo);
writeb(ebrg & 0xff, &up->regs->w.bgr);
writeb((readb(&up->regs->rw.ccr2) & ~0xc0) | ((ebrg >> 2) & 0xc0),
&up->regs->rw.ccr2);

writeb(readb(&up->regs->rw.mode) | SAB82532_MODE_RAC, &up->regs->rw.mode);

/* Now schedule a register update when the chip's
* transmitter is idle.
*/
up->cached_mode |= SAB82532_MODE_RAC;
set_bit(SAB82532_REGS_PENDING, &up->irqflags);
if (test_bit(SAB82532_XPR, &up->irqflags))
sunsab_tx_idle(up);
}

/* port->lock is not held. */
Expand Down Expand Up @@ -1084,11 +1115,13 @@ static void __init sunsab_init_hw(void)
up->pvr_dsr_bit = (1 << 3);
up->pvr_dtr_bit = (1 << 2);
}
writeb((1 << 1) | (1 << 2) | (1 << 4), &up->regs->w.pvr);
writeb(readb(&up->regs->rw.mode) | SAB82532_MODE_FRTS,
&up->regs->rw.mode);
writeb(readb(&up->regs->rw.mode) | SAB82532_MODE_RTS,
&up->regs->rw.mode);
up->cached_pvr = (1 << 1) | (1 << 2) | (1 << 4);
writeb(up->cached_pvr, &up->regs->w.pvr);
up->cached_mode = readb(&up->regs->rw.mode);
up->cached_mode |= SAB82532_MODE_FRTS;
writeb(up->cached_mode, &up->regs->rw.mode);
up->cached_mode |= SAB82532_MODE_RTS;
writeb(up->cached_mode, &up->regs->rw.mode);

up->tec_timeout = SAB82532_MAX_TEC_TIMEOUT;
up->cec_timeout = SAB82532_MAX_CEC_TIMEOUT;
Expand Down
1 change: 1 addition & 0 deletions drivers/serial/sunsab.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -126,6 +126,7 @@ union sab82532_irq_status {
/* irqflags bits */
#define SAB82532_ALLS 0x00000001
#define SAB82532_XPR 0x00000002
#define SAB82532_REGS_PENDING 0x00000004

/* RFIFO Status Byte */
#define SAB82532_RSTAT_PE 0x80
Expand Down

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