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Deleted the workaround for lockup of certain (hopefully no longer used)

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UARTs when their divisor latch registers are selected while they are
doing output.  Waiting for (some) output to drain is not permitted for
the TCSANOW case of tcsetattr().  NIST-PCTS easily detects bugs like
this by testing at at speeds that no one would want to use (50 bps).

Deleted stale comments related to flushing i/o.  Flushing works properly
for 16550s according to NIST-PCTS (it can't work properly for 16450s).
This finishes fixing all sio(16550)-related bugs found by NIST-PCTS.
This commit is contained in:
Bruce Evans 1998-11-22 10:47:42 +00:00
parent 121d04904e
commit 8280a33470
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=41289
1 changed files with 1 additions and 51 deletions
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52
sys/i386/isa/sio.c
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@ -31,7 +31,7 @@
* SUCH DAMAGE.
*
* from: @(#)com.c 7.5 (Berkeley) 5/16/91
* $Id: sio.c,v 1.216 1998/10/22 05:58:40 bde Exp $
* $Id: sio.c,v 1.217 1998/11/22 09:41:12 bde Exp $
*/
#include "opt_comconsole.h"
@ -2037,11 +2037,9 @@ comparam(tp, t)
int divisor;
u_char dlbh;
u_char dlbl;
int error;
Port_t iobase;
int s;
int unit;
int txtimeout;
/* do historical conversions */
if (t->c_ispeed == 0)
@ -2107,54 +2105,8 @@ comparam(tp, t)
outb(iobase + com_fifo, com->fifo_image);
}
/*
* Some UARTs lock up if the divisor latch registers are selected
* while the UART is doing output (they refuse to transmit anything
* more until given a hard reset). Fix this by stopping filling
* the device buffers and waiting for them to drain. Reading the
* line status port outside of siointr1() might lose an output
* interrupt, but this will be fixed by (re)starting output.
*/
disable_intr();
retry:
com->state &= ~CS_TTGO;
txtimeout = tp->t_timeout;
enable_intr();
while ((inb(com->line_status_port) & (LSR_TSRE | LSR_TXRDY))
!= (LSR_TSRE | LSR_TXRDY)) {
tp->t_state |= TS_SO_OCOMPLETE;
error = ttysleep(tp, TSA_OCOMPLETE(tp), TTIPRI | PCATCH,
"siotx", hz / 100);
if ( txtimeout != 0
&& (!error || error == EAGAIN)
&& (txtimeout -= hz / 100) <= 0
)
error = EIO;
if (com->gone)
error = ENODEV;
if (error != 0 && error != EAGAIN) {
if (!(tp->t_state & TS_TTSTOP)) {
disable_intr();
com->state |= CS_TTGO;
enable_intr();
}
splx(s);
return (error);
}
}
disable_intr(); /* very important while com_data is hidden */
/*
* XXX - clearing CS_TTGO is not sufficient to stop further output,
* because siopoll() calls comstart() which usually sets it again
* because TS_TTSTOP is clear. Setting TS_TTSTOP would not be
* sufficient, for similar reasons.
*/
if ((inb(com->line_status_port) & (LSR_TSRE | LSR_TXRDY))
!= (LSR_TSRE | LSR_TXRDY))
goto retry;
if (divisor != 0) {
outb(iobase + com_cfcr, cfcr | CFCR_DLAB);
/*
@ -2346,7 +2298,6 @@ siostop(tp, rw)
/* XXX avoid h/w bug. */
if (!com->esp)
#endif
/* XXX does this flush everything? */
outb(com->iobase + com_fifo,
FIFO_XMT_RST | com->fifo_image);
com->obufs[0].l_queued = FALSE;
@ -2362,7 +2313,6 @@ siostop(tp, rw)
/* XXX avoid h/w bug. */
if (!com->esp)
#endif
/* XXX does this flush everything? */
outb(com->iobase + com_fifo,
FIFO_RCV_RST | com->fifo_image);
com_events -= (com->iptr - com->ibuf);