"Brown, David (dbrown03)" <DBrown03 at harris.com> writes:
> I see characters dropped at the end of a write to a serial port. Surely
> that isn't normal.
> I'm using the current MontaVista 2.2.13 kernel patched for my custom
> 860-based board. The serial ports are running at 9600.
>
> When I do this:
> init-2.00# help while >/dev/ttyS1
[snip]
> well. Could it be that when a serial port is closed, the uart is disabled
> immediately instead of waiting for output to finish?
Right on target.
rs_8xx_wait_until_sent() will wait for the *first* buffer descriptor
to be finished, instead of waiting for the last one as it should.
This patch fixes that problem:
diff -bu uart.orig uart.c
--- uart.c.orig Wed May 3 20:25:09 2000
+++ uart.c Fri Apr 28 20:08:15 2000
@@ -1710,6 +1718,13 @@
* be at least two characters waiting to be sent after the buffers
* are empty.
*/
+ bdp = info->tx_cur;
+ /* We want to wait for the last buffer, not the first. */
+ if (bdp == info->tx_bd_base) {
+ bdp += (TX_NUM_FIFO-1);
+ } else {
+ bdp--;
+ }
do {
#ifdef SERIAL_DEBUG_RS_WAIT_UNTIL_SENT
printk("lsr = %d (jiff=%lu)...", lsr, jiffies);
@@ -1721,7 +1736,6 @@
break;
if (timeout && ((orig_jiffies + timeout) < jiffies))
break;
- bdp = info->tx_cur;
} while (bdp->cbd_sc & BD_SC_READY);
current->state = TASK_RUNNING;
#ifdef SERIAL_DEBUG_RS_WAIT_UNTIL_SENT
There is also a problem with kernel messages being truncated when
an application open the serial console. This patch should fix that:
diff -bu uart.orig uart.c
--- uart.c.orig Wed May 3 20:25:09 2000
+++ uart.c Fri Apr 28 20:08:15 2000
@@ -915,8 +909,20 @@
info->read_status_mask &= ~BD_SC_EMPTY;
save_flags(flags); cli();
+ /* Make sure last buffer has been sent. */
+ {
+ volatile cbd_t *bdp;
+ bdp = info->tx_cur;
+ if (bdp == info->tx_bd_base) {
+ bdp += (TX_NUM_FIFO-1);
+ } else {
+ bdp--;
+ }
+ while (bdp->cbd_sc & BD_SC_READY);
+ }
+
/* Start bit has not been added (so don't, because we would just
* subtract it later), and we need to add one for the number of
* stops bits (there is always at least one).
*/
bits++;
//Marcus
--
-------------------------------+-----------------------------------
Marcus Sundberg | Phone: +46 707 452062
Embedded Systems Consultant | Email: marcus at cendio.se
Cendio Systems AB | http://www.cendio.se/
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