netdev - Re: Question on i40e PCIe relaxed ordering (RO)

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Message-ID: <1467231519.3404.11.camel@gmail.com>
Date:	Wed, 29 Jun 2016 13:18:39 -0700
From:	Greg <gvrose8192@...il.com>
To:	tndave <tushar.n.dave@...cle.com>
Cc:	intel-wired-lan@...ts.osuosl.org,
	"Kirsher, Jeffrey T" <jeffrey.t.kirsher@...el.com>,
	netdev <netdev@...r.kernel.org>
Subject: Re: Question on i40e PCIe relaxed ordering (RO)

On Wed, 2016-06-29 at 13:05 -0700, tndave wrote:
> Hi,
> 
> Running iperf tcp test on 2 sparc systems with i40e connected back to
> back, I see huge number of 'port.rx_dropped' (on iperf server). Based on
> past experience with ixgbe, this could very well because of PCIe RO
> (relaxed ordering) not enabled.
> 
> I am trying to confirm RO is enabled. i40e datasheet mentioned RO
> settings in 3 different sections:
> 
> 1. section 10.2.2.2.38 PCIe Global Config 2 - GLPCI_CNF2 register
> contains global status fields of PCIe configuration. The bit 0 of the
> register is "RO_DIS". If this bit is set to 1 RO is disabled.
> 
> RO_DIS in my setup is 0 imply RO is not disabled.
> 
> 2. section 12.3.5.5 Device Control Register (0xA8; RW) has bit 4
> that enable/disable RO. This is pcie cap register.
> 
> In my i40e pcie config space value at offset 0xA8 is "2110". i.e 4th bit
> set to 1 imply RO is enabled.
> 
> 3. section 3.1.2.7.2 mentions some relaxed ordering rules
> e.g. "The GLLAN_RCTL.RXDESCRDROEN bit (loaded from NVM) enables relaxed
> ordering for Rx descriptor reads"
> 
> However, GLLAN_RCTL register definition has not bit like RXDESCRDROEN.
> Same goes for GLLAN_TCTL.TXDESCRDROEN.
> 
> Am I missing anything? please advise.

I would try posting this question to the e1000 developer list over at
Source Forge.  The Intel customer support folks used to monitor that
list closely when I was there, hopefully they still are.

Regards,

- Greg

> 
> Thanks.
> 
> -Tushar
> 
> (Ref:http://www.intel.com/content/dam/www/public/us/en/documents/datasheets/xl710-10-40-controller-datasheet.pdf)
> 
> 
>