netdev - Re: [PATCH v2 net 1/1] amd-xgbe: fix active cable

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Date:   Fri, 11 Nov 2022 17:00:22 +0100
From:   Thomas Kupper <thomas@...per.org>
To:     Tom Lendacky <thomas.lendacky@....com>, netdev@...r.kernel.org
Cc:     Jakub Kicinski <kuba@...nel.org>,
        Raju Rangoju <Raju.Rangoju@....com>
Subject: Re: [PATCH v2 net 1/1] amd-xgbe: fix active cable


On 11/11/22 15:18, Tom Lendacky wrote:
> On 11/11/22 02:46, Thomas Kupper wrote:
>> When determine the type of SFP, active cables were not handled.
>>
>> Add the check for active cables as an extension to the passive cable check.
> 
> Is this fixing a particular problem? What SFP is this failing for? A more descriptive commit message would be good.
> 
> Also, since an active cable is supposed to be advertising it's capabilities in the eeprom, maybe this gets fixed via a quirk and not a general check this field.

It is fixing a problem regarding a Mikrotik S+AO0005 AOC cable (we were in contact back in Feb to May). And your right I should have been more descriptive in the commit message.

>>
>> Fixes: abf0a1c2b26a ("amd-xgbe: Add support for SFP+ modules")
>> Signed-off-by: Thomas Kupper <thomas.kupper@...il.com>
>> ---
>>   drivers/net/ethernet/amd/xgbe/xgbe-phy-v2.c | 5 +++--
>>   1 file changed, 3 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/net/ethernet/amd/xgbe/xgbe-phy-v2.c b/drivers/net/ethernet/amd/xgbe/xgbe-phy-v2.c
>> index 4064c3e3dd49..1ba550d5c52d 100644
>> --- a/drivers/net/ethernet/amd/xgbe/xgbe-phy-v2.c
>> +++ b/drivers/net/ethernet/amd/xgbe/xgbe-phy-v2.c
>> @@ -1158,8 +1158,9 @@ static void xgbe_phy_sfp_parse_eeprom(struct xgbe_prv_data *pdata)
>>       }
>>
>>       /* Determine the type of SFP */
>> -    if (phy_data->sfp_cable == XGBE_SFP_CABLE_PASSIVE &&
>> -        xgbe_phy_sfp_bit_rate(sfp_eeprom, XGBE_SFP_SPEED_10000))
>> +    if ((phy_data->sfp_cable == XGBE_SFP_CABLE_PASSIVE ||
>> +         phy_data->sfp_cable == XGBE_SFP_CABLE_ACTIVE) &&
>> +         xgbe_phy_sfp_bit_rate(sfp_eeprom, XGBE_SFP_SPEED_10000))
> 
> This is just the same as saying:
> 
>     if (xgbe_phy_sfp_bit_rate(sfp_eeprom, XGBE_SFP_SPEED_10000))
> 
> since the sfp_cable value is either PASSIVE or ACTIVE.
> 
> I'm not sure I like fixing whatever issue you have in this way, though. If anything, I would prefer this to be a last case scenario and be placed at the end of the if-then-else block. But it may come down to applying a quirk for your situation.

I see now that this cable is probably indeed not advertising its capabilities correctly, I didn't understand what Shyam did refer to in his mail from June 6.

Unfortunately I haven't hear back from you guys after June 6 so I tried to fix it myself ... but do lack the knowledge in that area.

A quirk seems a good option.

>From my point of view this patch can be cancelled/aborted/deleted.
I'll look into how to fix it using a quirk but maybe I'm not the hest suited candidate to do it.

/Thomas

> 
> Thanks,
> Tom
> 
>>           phy_data->sfp_base = XGBE_SFP_BASE_10000_CR;
>>       else if (sfp_base[XGBE_SFP_BASE_10GBE_CC] & XGBE_SFP_BASE_10GBE_CC_SR)
>>           phy_data->sfp_base = XGBE_SFP_BASE_10000_SR;
>> -- 
>> 2.34.1
>>