Hi Jack,
On Wed, Jan 23, 2013 at 2:58 PM, Ryan Stone <ryst...@gmail.com> wrote:
> On Wed, Jan 23, 2013 at 2:13 AM, Neel Natu <neeln...@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
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