netdev - Re: [EXT] Re: [net-next PATCH 0/2] Introduce mbox tracepoints for Octeontx2

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Date:   Thu, 17 Sep 2020 16:00:03 +0530
From:   sundeep subbaraya <sundeep.lkml@...il.com>
To:     Jiri Pirko <jiri@...nulli.us>
Cc:     Jakub Kicinski <kuba@...nel.org>,
        Sunil Kovvuri Goutham <sgoutham@...vell.com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Subbaraya Sundeep Bhatta <sbhatta@...vell.com>
Subject: Re: [EXT] Re: [net-next PATCH 0/2] Introduce mbox tracepoints for Octeontx2

On Thu, Sep 17, 2020 at 11:34 AM Jiri Pirko <jiri@...nulli.us> wrote:
>
> Wed, Sep 16, 2020 at 07:19:36PM CEST, sundeep.lkml@...il.com wrote:
> >On Wed, Sep 16, 2020 at 4:04 PM Jiri Pirko <jiri@...nulli.us> wrote:
> >>
> >> Mon, Sep 07, 2020 at 12:59:45PM CEST, sundeep.lkml@...il.com wrote:
> >> >Hi Jakub,
> >> >
> >> >On Sat, Sep 5, 2020 at 2:07 AM Jakub Kicinski <kuba@...nel.org> wrote:
> >> >>
> >> >> On Fri, 4 Sep 2020 12:29:04 +0000 Sunil Kovvuri Goutham wrote:
> >> >> > > >No, there are 3 drivers registering to 3 PCI device IDs and there can
> >> >> > > >be many instances of the same devices. So there can be 10's of instances of
> >> >> > > AF, PF and VFs.
> >> >> > >
> >> >> > > So you can still have per-pci device devlink instance and use the tracepoint
> >> >> > > Jakub suggested.
> >> >> > >
> >> >> >
> >> >> > Two things
> >> >> > - As I mentioned above, there is a Crypto driver which uses the same mbox APIs
> >> >> >   which is in the process of upstreaming. There also we would need trace points.
> >> >> >   Not sure registering to devlink just for the sake of tracepoint is proper.
> >> >> >
> >> >> > - The devlink trace message is like this
> >> >> >
> >> >> >    TRACE_EVENT(devlink_hwmsg,
> >> >> >      . . .
> >> >> >         TP_printk("bus_name=%s dev_name=%s driver_name=%s incoming=%d type=%lu buf=0x[%*phD] len=%zu",
> >> >> >                   __get_str(bus_name), __get_str(dev_name),
> >> >> >                   __get_str(driver_name), __entry->incoming, __entry->type,
> >> >> >                   (int) __entry->len, __get_dynamic_array(buf), __entry->len)
> >> >> >    );
> >> >> >
> >> >> >    Whatever debug message we want as output doesn't fit into this.
> >> >>
> >> >> Make use of the standard devlink tracepoint wherever applicable, and you
> >> >> can keep your extra ones if you want (as long as Jiri don't object).
> >> >
> >> >Sure and noted. I have tried to use devlink tracepoints and since it
> >> >could not fit our purpose I used these.
> >>
> >> Why exactly the existing TP didn't fit your need?
> >>
> >Existing TP has provision to dump skb and trace error strings with
> >error code but
> >we are trying to trace the entire mailbox flow of the AF/PF and VF
> >drivers. In particular
> >we trace the below:
> >    message allocation with message id and size at initiator.
> >    number of messages sent and total size.
> >    check message requester id, response id and response code after
> >reply is received.
> >    interrupts happened on behalf of mailboxes in the entire process
> >with source and receiver of interrupt along with isr status.
> >    error like initiator timeout waiting for response.
> >  All the above are relevant and are required for Octeontx2 only hence
> >used own tracepoints.
>
> You can still use devlink_hwmsg for the actual data exchanged between
> the driver and hw. For the rest, you can have driver-specific TPs.
>
>
I totally got your point and adding devlink to our drivers is work in progress
since we got a similar comment from Jakub for a patch previously:
https://www.mail-archive.com/netdev@vger.kernel.org/msg341414.html
All the errors in the drivers will be turned to devlink TP in future.
This patchset is a bit different since it traces mailbox messages state machine
at low level and does not even trace message data exchanged between
driver and hw.

Thanks,
Sundeep

> >
> >Thanks,
> >Sundeep
> >
> >> >
> >> >Thanks,
> >> >Sundeep