netdev - Re: [PATCH 01/15] octeontx2-af: Interface backpressure configuration support

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Message-ID: <CA+sq2Cd63iyhw_=EC_=NL9+QWzRHi_0Vu0d1WAuiDhGRntAYTg@mail.gmail.com>
Date:   Tue, 19 Nov 2019 13:00:12 +0530
From:   Sunil Kovvuri <sunil.kovvuri@...il.com>
To:     Jakub Kicinski <jakub.kicinski@...ronome.com>
Cc:     Linux Netdev List <netdev@...r.kernel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Geetha sowjanya <gakula@...vell.com>,
        Sunil Goutham <sgoutham@...vell.com>
Subject: Re: [PATCH 01/15] octeontx2-af: Interface backpressure configuration support

On Tue, Nov 19, 2019 at 2:42 AM Jakub Kicinski
<jakub.kicinski@...ronome.com> wrote:
>
> On Sun, 17 Nov 2019 21:44:12 +0530, sunil.kovvuri@...il.com wrote:
> > From: Geetha sowjanya <gakula@...vell.com>
> >
> > Enables backpressure and assigns BPID for CGX and LBK channels.
> > 96xx support upto 512 BPIDs, these BPIDs are statically divided
> > across CGX/LBK/SDP interfaces as follows.
> > BPIDs   0 - 191 are mapped to LMAC channels.
> > BPIDs 192 - 255 are mapped to LBK channels.
> > BPIDs 256 - 511 are mapped to SDP channels.
> >
> > BPIDs across CGX LMAC channels are divided as follows.
> > CGX(0)_LMAC(0)_CHAN(0 - 15) mapped to BPIDs(0 - 15)
> > CGX(0)_LMAC(1)_CHAN(0 - 15) mapped to BPIDs(16 - 31)
> > .......
> > CGX(1)_LMAC(0)_CHAN(0 - 15) mapped to BPIDs(64 - 79)
> > ....
> >
> > Signed-off-by: Geetha sowjanya <gakula@...vell.com>
> > Signed-off-by: Sunil Goutham <sgoutham@...vell.com>
>
> Can you explain what is being done here from user perspective?
> How is this thing configured? Looks like you just added some
> callbacks for device-originating events?
>

Yes these are mbox handlers which help the netdev and userspace drivers to
configure hardware. The hardware functionality is divided across three entities.
The AF - Admin function, which has the highest privilege to configure
various HW blocks.
The SRIOV PF & VFs, Netdev or userspace drivers register to these
devices and send
communicate with the AF via mbox for configuration, information (eg
stats, hw capabilities) retrieval.

This patchset adds mbox handlers into the AF driver. Right after this
patchset we will submit the
netdev driver patches which will have ethtool etc support with which
user can configure HW.

> And please keep the acronyms which are meaningless to anyone
> upstream to a minimum.

Sure, will try, in this instance the commit message is needed for
future reference
incase someone working on this platform need to understand how the backpressure
IDs (BPIDs) are divided across various physical links through which
traffic flows.

Thanks,
Sunil.