netdev - Re: [PATCH 12/15] habanalabs/gaudi: add debugfs entries for the NIC

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Message-ID: <20200916093840.27112c98@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
Date:   Wed, 16 Sep 2020 09:38:40 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     Oded Gabbay <oded.gabbay@...il.com>
Cc:     Omer Shpigelman <oshpigelman@...ana.ai>,
        "Linux-Kernel@...r. Kernel. Org" <linux-kernel@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        SW_Drivers <SW_Drivers@...ana.ai>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH 12/15] habanalabs/gaudi: add debugfs entries for the NIC

On Tue, 15 Sep 2020 15:57:16 +0300 Oded Gabbay wrote:
> On Mon, Sep 14, 2020 at 7:50 PM Jakub Kicinski <kuba@...nel.org> wrote:
> > What's the use for a networking device which only communicates with
> > itself, other than testing?  
> 
> No use, and we do have a suite of tests that runs from user-space on
> the device after we move the interfaces to loopback mode.
> The main problem, as Omer said, is that we have two H/W bugs:
> 
> 1. Where you need to reset the entire SoC in case you want to move a
> single interface into (or out of) loopback mode. So doing it via
> ethtool will cause a reset to the entire SoC, and if you want to move
> all 10 ports to loopback mode, you need to reset the device 10 times
> before you can actually use that.
> 
> 2. Our 10 ports are divided into 5 groups of 2 ports each, from H/W
> POV. That means if you move port 0 to loopback mode, it will affect
> port 1 (and vice-versa). I don't think we want that behavior.
> 
> That's why we need this specific exception to the rule and do it via
> debugfs. I understand it is not common practice, but due to H/W bugs
> we can't workaround, we ask this exception.

Are those tests open source?

Are you sure you need this upstream? Are your users going to run those
tests?