Re: [PATCH 0/2] at803x: don't power-down SGMII link

[Zefir Kurtisi]

On 10/25/2016 07:31 PM, Timur Tabi wrote:
> Zefir Kurtisi wrote:
>> In a device where the ar8031 operates in SGMII mode, we
>> observed that after a suspend-resume cycle in very rare
>> cases the copper side autonegotiation secceeds but the
>> SGMII side fails to come up.
>>
>> As a work-around, a patch was provided that on suspend and
>> resume powers the SGMII link down and up along with the
>> copper side. This fixed the observed failure, but
>> introduced a regression Timur Tabi observed: once the SGMII
>> is powered down, the PHY is inaccessible by the CPU and
>> with that e.g. can't be re-initialized after suspend.
>>
>> Since the original issue could not be reproduced by others,
>> this series provides an alternative handling:
>> * the first patch reverts the prvious fix that powers down
>>SGMII
>> * the second patch adds double-checking for the observed
>>failure condition
>>
>> Zefir Kurtisi (2):
>>Revert "at803x: fix suspend/resume for SGMII link"
>>at803x: double check SGMII side autoneg
> 
> Tested-by: Timur Tabi 
> 
> With these patches, the problem I was seeing no longer occurs, and the new 
> code
> does not appear to break anything.  As before, I still have never seen the
> original problem, but this patchset seems to work for both of us.
> 
Thanks for testing.

I could make the double checking configurable and disabled by default, but this
would render it useless to detect the potential issue in the field.

Re: [PATCH 0/2] at803x: don't power-down SGMII link

[Timur Tabi]

Zefir Kurtisi wrote:

In a device where the ar8031 operates in SGMII mode, we
observed that after a suspend-resume cycle in very rare
cases the copper side autonegotiation secceeds but the
SGMII side fails to come up.

As a work-around, a patch was provided that on suspend and
resume powers the SGMII link down and up along with the
copper side. This fixed the observed failure, but
introduced a regression Timur Tabi observed: once the SGMII
is powered down, the PHY is inaccessible by the CPU and
with that e.g. can't be re-initialized after suspend.

Since the original issue could not be reproduced by others,
this series provides an alternative handling:
* the first patch reverts the prvious fix that powers down
   SGMII
* the second patch adds double-checking for the observed
   failure condition

Zefir Kurtisi (2):
   Revert "at803x: fix suspend/resume for SGMII link"
   at803x: double check SGMII side autoneg


Tested-by: Timur Tabi 

With these patches, the problem I was seeing no longer occurs, and the 
new code does not appear to break anything.  As before, I still have 
never seen the original problem, but this patchset seems to work for 
both of us.


--
Qualcomm Datacenter Technologies, Inc. as an affiliate of Qualcomm
Technologies, Inc.  Qualcomm Technologies, Inc. is a member of the
Code Aurora Forum, a Linux Foundation Collaborative Project.