Date:   Fri, 22 Dec 2017 16:22:26 -0800
From:   Tim Harvey <tharvey@...eworks.com>
To:     David Daney <ddaney@...iumnetworks.com>
Cc:     Andrew Lunn <andrew@...n.ch>, Sunil Goutham <sgoutham@...ium.com>,
        netdev <netdev@...r.kernel.org>
Subject: Re: thunderx sgmii interface hang

On Fri, Dec 22, 2017 at 3:00 PM, David Daney <ddaney@...iumnetworks.com> wrote:
> On 12/22/2017 02:19 PM, Tim Harvey wrote:
>>
>> On Tue, Dec 19, 2017 at 12:52 PM, Andrew Lunn <andrew@...n.ch> wrote:
>>>
>>> On Mon, Dec 18, 2017 at 01:53:47PM -0800, Tim Harvey wrote:
>>>>
>>>> On Wed, Dec 13, 2017 at 11:43 AM, Andrew Lunn <andrew@...n.ch> wrote:
>>>>>>
>>>>>> The nic appears to work fine (pings, TCP etc) up until a performance
>>>>>> test is attempted.
>>>>>> When an iperf bandwidth test is attempted the nic ends up in a state
>>>>>> where truncated-ip packets are being sent out (per a tcpdump from
>>>>>> another board):
>>>>>
>>>>>
>>>>> Hi Tim
>>>>>
>>>>> Are pause frames supported? Have you tried turning them off?
>>>>>
>>>>> Can you reproduce the issue with UDP? Or is it TCP only?
>>>>>
>>>>
>>>> Andrew,
>>>>
>>>> Pause frames don't appear to be supported yet and the issue occurs
>>>> when using UDP as well as TCP. I'm not clear what the best way to
>>>> troubleshoot this is.
>>>
>>>
>>> Hi Tim
>>>
>>> Is pause being negotiated? In theory, it should not be. The PHY should
>>> not offer it, if the MAC has not enabled it. But some PHY drivers are
>>> probably broken and offer pause when they should not.
>>>
>>> Also, can you trigger the issue using UDP at say 75% the maximum
>>> bandwidth. That should be low enough that the peer never even tries to
>>> use pause.
>>>
>>> All this pause stuff is just a stab in the dark. Something else to try
>>> is to turn off various forms off acceleration, ethtook -K, and see if
>>> that makes a difference.
>>>
>>
>> Andrew,
>>
>> Currently I'm not using the DP83867_PHY driver (after verifying the
>> issue occurs with or without that driver).
>>
>> It does not occur if I limit UDP (ie 950mbps). I disabled all offloads
>> and the issue still occurs.
>>
>> I have found that once the issue occurs I can recover to a working
>> state by clearing/setting BGX_CMRX_CFG[BGX_EN] and once I encounter
>> the issue and recover with that, I can never trigger the issue again.
>> If toggle that register bit upon power-up before the issue occurs it
>> will still occur.
>>
>> The CN80XX reference manual describes BGX_CMRX_CFG[BGX_EN] as:
>> - when cleared all dedicated BGX context state for LMAC (state
>> machine, FIFOs, counters etc) are reset and LMAC access to shared BGX
>> resources (data path, serdes lanes) is disabled
>> - when set LMAC operation is enabled (link bring-up, sync, and tx/rx
>> of idles and fault sequences)
>
>
> You could try looking at
> BGXX_GMP_PCS_INTX
> BGXX_GMP_GMI_RXX_INT
> BGXX_GMP_GMI_TXX_INT
>
> Those are all W1C registers that should contain all zeros.  If they don't,
> just write back to them to clear before running a test.
>
> If there are bits asserting in these when the thing gets wedged up, it might
> point to a possible cause.

David,

BGXX_GMP_GMI_TXX_INT[UNDFLW] is getting set when the issue is
triggered. From CN80XX-HM-1.2P this is caused by:

"In the unlikely event that P2X data cannot keep the GMP TX FIFO full,
the SGMII/1000BASE-X/ QSGMII packet transfer will underflow. This
should be detected by the receiving device as an FCS error.
Internally, the packet is drained and lost"

Perhaps this needs to be caught and handled in some way. There's some
interrupt handlers in nicvf_main.c yet I'm not clear where to hook up
this one.

>
> You could also look at these RO registers:
> BGXX_GMP_PCS_TXX_STATES
> BGXX_GMP_PCS_RXX_STATES
>

These show the same before/after triggering the issue and
RX_BAD/TX_BAD are still 0.

Tim

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