Messages in this thread | | | Date | Wed, 04 Jan 2012 19:41:47 +0100 | From | Jiri Slaby <> | Subject | Re: UV serial regression since 2.6.36 |
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On 12/06/2011 11:34 PM, Jiri Slaby wrote: > Hi, > > In short, the issue causes serial port traffic to stop after some time > on UV machines. Only when serial is used as a console. It worked > perfectly with 2.6.32. It's a standard 16550 on 0x3f8 (well, it's > emulated to be at that port). Also in the PNP subsys. > > To reproduce that 'debug' kernel parameter must not be used. > > The root cause seems to be that the serial "chip" there has problems > with interrupts. It generates some but doesn't indicate it's the source > or somebody clears it (NOINT is set). And when it is supposed to > generate one (on THRE), it does not. So there are bytes in the TX buffer > which are never sent. Until the port is kicked e.g. by "echo h > > /proc/sysrq-trigger". > > The unhandled interrupts were always an issue, but somehow hidden. It > became a real problem with patches post 2.6.32. > > I bisected it to these two commits _together_: > > commit 3f582b8c11014e4ce310d9839fb335164195333f > Author: Arnd Bergmann <arnd@arndb.de> > Date: Tue Jun 29 22:31:40 2010 +0200 > > serial: fix termios settings in open > > AND > > commit 74c2107759dc6efaa1b9127014be58a742a1e7ac > Author: Alan Cox <alan@linux.intel.com> > Date: Tue Jun 1 22:53:00 2010 +0200 > > serial: Use block_til_ready helper > > Those reverted on the top of 2.6.37 makes it work again. Those reverted > on the top of 3.0 plus mine 3 reverted which removed update_set_termios > completely makes it work again. > > I didn't look closely to why those patches are causing that. Like > c_cflag copy in uart_update_termios and "tty->termios->c_cflag & CBAUD" > test in tty_port_block_til_ready don't look good to me...
My vacation is over. I suppose you haven't had a chance to take a look into the regression? (Just in case any of you is looking into that right now to not duplicate the effort.)
> thanks, -- js suse labs
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