Dealing with silo overflow and interrupt-level buffer overflow in sio(4)

[Dirk-Willem van Gulik]

I found that for virtually all GPRS and UMTS cards I tried that I get so
many interopt and silo overflow errors as to virtually make the card
unusable.

Attached patch below allows one to increase the buffer a bit; relative to
the speed of the connection.

Thanks,

Dw.


*** sio.c.orig  Wed Nov 16 21:49:23 2005
--- sio.c       Wed Nov 16 21:57:46 2005
***************
*** 1906,1911 ****
--- 1907,1915 ----
        return (0);
  }

+
+ static int cp4tick_rate = 4;
+ TUNABLE_INT("machdep.sio.cp4tick_rate", &cp4tick_rate);
  /*
   * This function must be called with the sio_lock mutex released and will
   * return with it obtained.
***************
*** 1926,1932 ****
         * (about 3 ticks if input flow control is not used or not honoured,
         * but a bit less for CS5-CS7 modes).
         */
!       cp4ticks = 40 * speed / 10 / hz * 4;
        for (ibufsize = 128; ibufsize < cp4ticks;)
                ibufsize <<= 1;
        if (ibufsize == com->ibufsize) {
--- 1930,1936 ----
         * (about 3 ticks if input flow control is not used or not honoured,
         * but a bit less for CS5-CS7 modes).
         */
!       cp4ticks = (cp4tick_rate ? cp4tick_rate : 4) * speed / 10 / hz;
        for (ibufsize = 128; ibufsize < cp4ticks;)
                ibufsize <<= 1;
        if (ibufsize == com->ibufsize) {root at builld-jv#
diff -c sio.4.orig
sio.4
*** sio.4.orig  Wed Nov 16 21:57:33 2005
--- sio.4       Wed Nov 16 22:02:04 2005
***************
*** 363,368 ****
--- 363,381 ----
  .Pp
  The device numbers are made from the set [0-9a-v] so that more than
  10 ports can be supported.
+ .Sh TUNABLES
+ The driver supports the following tunable parameters, which may be
+ added to
+ .Pa /boot/loader.conf
+ or set via the
+ .Xr sysctl 8
+ command:
+ .Bl -tag -width ".Cm  machdep.sio.cp4tick_rate " -compact
+ .It Cm machdep.sio.cp4tick_rate
+ Rate by which to increase the buffer ti handle  softtty interrupt
+ latency. Default value is 4; to deal with about 2-3 ticks without
+ loss of  throughput or data.
+ .El
  .Sh DIAGNOSTICS
  .Bl -diag
  .It sio%d: silo overflow.
***************
*** 370,382 ****
  .El
  .Bl -diag
  .It sio%d: interrupt-level buffer overflow.
! Problem in the bottom half of the driver.
  .El
  .Bl -diag
  .It sio%d: tty-level buffer overflow.
  Problem in the application.
  Input has arrived faster than the given module could process it
! and some has been lost.
  .El
  .\" .Bl -diag
  .\" .It sio%d: reduced fifo trigger level to %d.
--- 383,395 ----
  .El
  .Bl -diag
  .It sio%d: interrupt-level buffer overflow.
! Problem in the bottom half of the driver. Try increasing
machdep.sio.cp4tick_rate.
  .El
  .Bl -diag
  .It sio%d: tty-level buffer overflow.
  Problem in the application.
  Input has arrived faster than the given module could process it
! and some has been lost. Try increasing machdep.sio.cp4tick_rate.
  .El
  .\" .Bl -diag
  .\" .It sio%d: reduced fifo trigger level to %d.