* 8250 regression: infinite interrupts
@ 2012-01-27 14:22 Jiri Slaby
2012-01-28 10:50 ` Linus Walleij
0 siblings, 1 reply; 2+ messages in thread
From: Jiri Slaby @ 2012-01-27 14:22 UTC (permalink / raw)
To: philippe.langlais, Alan Cox, Greg KH, Linux kernel mailing list,
linux-serial
Hi,
the commit below causes infinite interrupts to be generated on some
chips. Namely on IBM x3850 M2.
commit 235dae5d094c415fcf0fc79fa637f1901bc8afe2
Author: Philippe Langlais <philippe.langlais@stericsson.com>
Date: Thu Jul 29 17:13:57 2010 +0200
U6715 16550A serial driver support
The culprit is the added size_fifo call proper in autoconfig_16550a. It
returns 16, but the chip is confused by what the function does at that
point. It is yet to be investigated why. Any ideas at this stage why
this could be a problem?
thanks,
--
js
suse labs
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: 8250 regression: infinite interrupts
2012-01-27 14:22 8250 regression: infinite interrupts Jiri Slaby
@ 2012-01-28 10:50 ` Linus Walleij
0 siblings, 0 replies; 2+ messages in thread
From: Linus Walleij @ 2012-01-28 10:50 UTC (permalink / raw)
To: Jiri Slaby
Cc: philippe.langlais, Alan Cox, Greg KH, Linux kernel mailing list,
linux-serial
2012/1/27 Jiri Slaby <jslaby@suse.cz>:
> The culprit is the added size_fifo call proper in autoconfig_16550a. It
> returns 16, but the chip is confused by what the function does at that
> point. It is yet to be investigated why. Any ideas at this stage why
> this could be a problem?
The header says the function sometimes fail :-/
What it does is set the UART in loopback mode and saturate it with
256 bytes to overflow the FIFO, then check how many chars
were in the FIFO to determine FIFO size.
Could it be that your variant does not clear the FIFO overflow
correctly and get stuck in some error state? Maybe try clearing
some error flags at the end of this function?
Yours,
Linus Walleij
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