From e4fdee8e3b41239242a8f421a28736ef8e08ca55 Mon Sep 17 00:00:00 2001 From: "David S. Miller" Date: Wed, 11 May 2005 11:34:32 -0700 Subject: [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 --- drivers/serial/sunsab.c | 109 +++++++++++++++++++++++++++++++----------------- 1 file changed, 71 insertions(+), 38 deletions(-) (limited to 'drivers/serial/sunsab.c') diff --git a/drivers/serial/sunsab.c b/drivers/serial/sunsab.c index 39b788d95e39..10e2990a40d4 100644 --- a/drivers/serial/sunsab.c +++ b/drivers/serial/sunsab.c @@ -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; }; /* @@ -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) @@ -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; @@ -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. */ @@ -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) { @@ -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); } @@ -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); @@ -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); @@ -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 @@ -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; @@ -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; @@ -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. */ @@ -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; -- cgit v1.2.3-59-g8ed1b