[SUNSAB]: Defer register updates until transmitter is idle.
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>
diff --git a/drivers/serial/sunsab.c b/drivers/serial/sunsab.c
index 39b788d..10e2990 100644
--- a/drivers/serial/sunsab.c
+++ b/drivers/serial/sunsab.c
@@ -61,6 +61,16 @@
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;
};
/*
@@ -236,6 +246,7 @@
}
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)
@@ -258,6 +269,7 @@
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;
@@ -397,21 +409,21 @@
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. */
@@ -450,6 +462,25 @@
}
/* 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)
{
struct uart_sunsab_port *up = (struct uart_sunsab_port *) port;
@@ -517,12 +548,16 @@
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);
}
@@ -566,8 +601,9 @@
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);
@@ -598,7 +634,6 @@
{
struct uart_sunsab_port *up = (struct uart_sunsab_port *) port;
unsigned long flags;
- unsigned char tmp;
spin_lock_irqsave(&up->port.lock, flags);
@@ -609,14 +644,13 @@
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
@@ -685,7 +719,6 @@
unsigned int iflag, unsigned int baud,
unsigned int quot)
{
- unsigned int ebrg;
unsigned char dafo;
int bits, n, m;
@@ -714,10 +747,11 @@
} 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;
@@ -770,16 +804,13 @@
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. */
@@ -1084,11 +1115,13 @@
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;
diff --git a/drivers/serial/sunsab.h b/drivers/serial/sunsab.h
index 686086f..b78e1f7 100644
--- a/drivers/serial/sunsab.h
+++ b/drivers/serial/sunsab.h
@@ -126,6 +126,7 @@
/* irqflags bits */
#define SAB82532_ALLS 0x00000001
#define SAB82532_XPR 0x00000002
+#define SAB82532_REGS_PENDING 0x00000004
/* RFIFO Status Byte */
#define SAB82532_RSTAT_PE 0x80