On Tue, Sep 02, 2014 at 01:15:37PM -0700, Tony Lindgren wrote:

* Sebastian Andrzej Siewior [off-list ref] [140902 11:40]:

quoted

On 09/01/2014 07:47 PM, Sebastian Andrzej Siewior wrote:

quoted

Comparing it with serial-omap I see the same thing: I takes approx the
same amount of data until the first one is displayed. After a lot of
"long" writes which wake the chip up from idle I manage to freeze both,
the serial-omap driver and mine driver.

So after some testing:
- it happens with omap-serial as well. Especially after disabling the
  LED trigger for both LEDs.

- it seemed that disabling the MDR1 check whether or not we lost
  context made the problem appear less often but it was a trick. Even
  with restoring the context each time I see the same problem.

- it seems to be easier to trigger with the LED trigger switched off.
  However sometimes it works for 10 minutes, sometimes it triggers
  after one.

- I see to face two kind of "deaths":
  - the LED still goes on and off and the uart just does not respond
    even if I tell the button print something on the screen (the button
    also changes the frequency of the LED so I know that the button is
    doing something).
    Also from dumping the content of /proc/interrupts it seems that a
    wake up is made, the uart should have restored the registers.

OK yeah this is the case I was seeing too. So do you just set the
LED triggers to none in sysfs to make it easier to reproduce?

quoted

  - one where the system is dead and the LED does not blink anymore.
    Also my button is dead.

This I don't think I've seen. This could also be the errata issue on
your earlier rev beagleboard-xm with off-idle.
 

quoted

- disabling DMA makes the problem not go away.

OK
 

quoted

- mdelay(25) in omap8250_lost_context() is long enough to drop the 403
  bytes I send in my testcase. That means I see only "good" characters.
  With this the box remained alive for 2h. However the uart died anyway.

I wonder if doing some TX on the uart restores it? So maybe try

$ while [ 1 ]; do date; sleep 10 done &

To have it occasionally print something in the background.

If there is a way to detect the hangup you may try to recover by
resetting the serial device using omap_hwmod_reset().

-- Sebastian
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