Subject: Re: [ISSUE: sky2 - rx error] Link stops working under heavy traffic load connected to a mv88e6176

From: Rafa Corvillo <[email-masked]>
Date: Tue, 16 May 2017 17:50:26 +0200

> On Tue, May 16, 2017 at 03:09:17PM +0200, Rafa Corvillo wrote:
>>>> Adding 8 bytes (sky2->netdev->mtu + ETH_HLEN + VLAN_HLEN + 8
>>>> (EDSA_HLEN)) does not fix the error, because the interface keep
>>>> having a maximum length of 1518 bytes (sky2->netdev->mtu + ETH_HLEN
>>>> + VLAN_HLEN).
>>>
>>> Did you check the value being written to here:
>>>
>>>          /*
>>>           * The receiver hangs if it receives frames larger than the
>>>           * packet buffer. As a workaround, truncate oversize frames, but
>>>           * the register is limited to 9 bits, so if you do frames > 2052
>>>           * you better get the MTU right!
>>>           */
>>>          thresh = sky2_get_rx_threshold(sky2);
>>>          if (thresh > 0x1ff)
>>>                  sky2_write32(hw, SK_REG(sky2->port, RX_GMF_CTRL_T), RX_TRUNC_OFF);
>>>          else {
>>>                  sky2_write16(hw, SK_REG(sky2->port, RX_GMF_TR_THR), thresh);
>>>                  sky2_write32(hw, SK_REG(sky2->port, RX_GMF_CTRL_T), RX_TRUNC_ON);
>>>          }
>>>
>>>
>>> What is thresh?
>>
>> The value of thresh is 380.
>
> So that is 1528.

Yes, this is the result of the roundup function.

>
> You could hack it and try 0x1ff.

I have forced the value of thresh to 0x1ff and the rx error still appears.

>
> Also, check that in sky2_rx_add(), le->length is set to 4K.
>

The value of le->length is set to 1520.

Rafa