Date: Mon, 28 Jan 2013 20:14:02 -0800 From: Neel Natu <neelnatu@gmail.com> To: Jack F Vogel <jfv@freebsd.org> Cc: freebsd-net <freebsd-net@freebsd.org>, Ryan Stone <rysto32@gmail.com> Subject: Re: e1000 serdes link flap Message-ID: <CAFgRE9FBgGSy4EQJrsKomZgwTTZmweeHpYHER4qWCP%2Bykr8sdw@mail.gmail.com> In-Reply-To: <CAFMmRNzA-s4T1T=NCZL1fWqop0Hr-WpPwJQfat1E-qugb4Jdcw@mail.gmail.com> References: <CAFgRE9EpskSJ=PHG0qhDoDE6eP1_yXTidOwnhr8q-M=G3UCHSQ@mail.gmail.com> <CAFMmRNzA-s4T1T=NCZL1fWqop0Hr-WpPwJQfat1E-qugb4Jdcw@mail.gmail.com>
next in thread | previous in thread | raw e-mail | index | archive | help
Hi Jack,
On Wed, Jan 23, 2013 at 2:58 PM, Ryan Stone <rysto32@gmail.com> wrote:
> On Wed, Jan 23, 2013 at 2:13 AM, Neel Natu <neelnatu@gmail.com> wrote:
>>
>> Hi,
>>
>> I am running into a problem in head with the e1000 link state
>> detection logic attached to a 82571EB serdes controller.
>>
>> The symptom is that the link state keeps flapping between "up" and "down".
>>
>> After I enabled the debug output in
>> 'e1000_check_for_serdes_link_82571()' this is what I see:
>> <snip>
>> e1000_check_for_serdes_link_82571
>> ctrl = 0x4c0241, status = 0x803a7, rxcw = 0x44000000
>> FORCED_UP -> AN_PROG
>> em6: link state changed to DOWN
>> e1000_check_for_serdes_link_82571
>> ctrl = 0x4c0201, status = 0x803a4, rxcw = 0x44000000
>> AN_PROG -> FORCED_UP
>> em6: link state changed to UP
>> e1000_check_for_serdes_link_82571
>> ctrl = 0x4c0241, status = 0x803a7, rxcw = 0x44000000
>> FORCED_UP -> AN_PROG
>> em6: link state changed to DOWN
>> </snip>
>>
>> The problem goes away if I apply the following patch to bring the link
>> state detection logic in line with the e1000e driver in Linux:
>>
>> Index: e1000_82571.c
>> ===================================================================
>> --- e1000_82571.c (revision 245766)
>> +++ e1000_82571.c (working copy)
>> @@ -1712,10 +1712,8 @@
>> * auto-negotiation in the TXCW register and
>> disable
>> * forced link in the Device Control register in
>> an
>> * attempt to auto-negotiate with our link
>> partner.
>> - * If the partner code word is null, stop forcing
>> - * and restart auto negotiation.
>> */
>> - if ((rxcw & E1000_RXCW_C) || !(rxcw &
>> E1000_RXCW_CW)) {
>> + if ((rxcw & E1000_RXCW_C) != 0) {
>> /* Enable autoneg, and unforce link up */
>> E1000_WRITE_REG(hw, E1000_TXCW,
>> mac->txcw);
>> E1000_WRITE_REG(hw, E1000_CTRL,
>>
>> I am not sure why the !(rxcw & E1000_RXCW_CW) check was added and the
>> e1000 SDM does not have any more information.
>>
>> Jack, can you take a look at the patch and commit if it looks alright?
>
>
> I have this change applied internally. I thought that it was something
> funny in my environment, so I never tried to push it upstream. Sorry for
> costing you time in having to debug this. :(
Are you planning to commit this patch?
I am happy to get you more information from my system if it helps you
get to the bottom of this quicker.
best
Neel
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?CAFgRE9FBgGSy4EQJrsKomZgwTTZmweeHpYHER4qWCP%2Bykr8sdw>