linux-kernel - Re: [PATCH v6 01/10] i3c: Add core I3C infrastructure

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Date:   Thu, 30 Aug 2018 14:57:36 +0100
From:   vitor <Vitor.Soares@...opsys.com>
To:     Przemyslaw Gaj <pgaj@...ence.com>,
        Boris Brezillon <boris.brezillon@...tlin.com>,
        vitor <Vitor.Soares@...opsys.com>
CC:     "linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
        Sekhar Nori <nsekhar@...com>, Wolfram Sang <wsa@...-dreams.de>,
        "linux-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>,
        Jonathan Corbet <corbet@....net>,
        "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Arnd Bergmann <arnd@...db.de>,
        Przemyslaw Sroka <psroka@...ence.com>,
        Arkadiusz Golec <agolec@...ence.com>,
        Alan Douglas <adouglas@...ence.com>,
        Bartosz Folta <bfolta@...ence.com>,
        Damian Kos <dkos@...ence.com>,
        Alicja Jurasik-Urbaniak <alicja@...ence.com>,
        Cyprian Wronka <cwronka@...ence.com>,
        Suresh Punnoose <sureshp@...ence.com>,
        Rafal Ciepiela <rafalc@...ence.com>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        Nishanth Menon <nm@...com>, Rob Herring <robh+dt@...nel.org>,
        Pawel Moll <pawel.moll@....com>,
        Mark Rutland <mark.rutland@....com>,
        Ian Campbell <ijc+devicetree@...lion.org.uk>,
        "Kumar Gala" <galak@...eaurora.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Xiang Lin <Xiang.Lin@...aptics.com>,
        Peter Rosin <peda@...ntia.se>
Subject: Re: [PATCH v6 01/10] i3c: Add core I3C infrastructure

Hi Przemyslaw


On 28-08-2018 13:55, Przemyslaw Gaj wrote:
> Hi Vitor,
>
> I have already implemented Mastership request/handover but we are waiting for Boris’s patch to be accepted and merged. Anyway, my comments below.
>
> On 8/28/18, 2:02 PM, "Boris Brezillon" <boris.brezillon@...tlin.com> wrote:
>
>      EXTERNAL MAIL
>      
>      
>      Hi Vitor,
>      
>      On Tue, 28 Aug 2018 12:50:12 +0100
>      vitor <Vitor.Soares@...opsys.com> wrote:
>      
>      > Hi Boris,
>      >
>      > The DT Bindings say "The node describing an I3C bus should be named
>      > i3c-master.". Do you have a field for secondary master?
>
> I think we don’t need separate field for secondary master. Main and secondary masters
> support similar functionalities. It’s enough to have this state internally and do mastership it it's needed.

Yes, you are right.

>
>      >
>      > On 24-08-2018 19:16, Boris Brezillon wrote:
>      > > Well, before even considering supporting secondary master registration,
>      > > we need to handle mastership handover. As for the DAA operation, it's
>      > > likely to be host specific, so we'll have to add a new hook to the
>      > > i3c_master_controller_ops struct.
>      > Do you mean when master try to delegate the bus ownership through
>      > GETACCMST? or to get the bus ownership with IBI-MR?
>      
>      I think we need to support both.
>
> I agree.

That's ok to me.

>      
>      >
>      > I think that could be useful to pass the ibi type on request_ibi(),
>      > there is some case where the master doesn't support IBI-MR.
>      
>      Actually, I was planning on making it completely separate from
>      regular slave IBIs. That is, the master controller driver would demux
>      the slave, MR and Hot Join IBIs, and if there's an MR request, queue a
>      mastership handover work to the workqueue (pretty much what we do for
>      Hot-Join already). Mastership handover is anyway likely to be IP
>      specific, so I don't think there's a need to make it look like a
>      regular IBI.
>
> I think it's better to have separate function to do mastership request.
>      
>      Regarding whether IBI-MR support should be exposed to the I3C framework
>      or not depends on how much will be automated on the framework side. I
>      don't the answer yet, but that's probably something will figure out
>      along the road.
>
> My current implementation is: when request_mastership field
> of i3c_master_controller_ops structure is set, master driver supports mastership requests.
> That's how I check if this is supported or not.
>      
>      Regards,
>      
>      Boris
>      
> Regards,
> Przemek
>
when you say request_mastership, do you mean the current master do the 
mastership hand-off or the secondary master request to be current master?

So, per my understanding since the Main master support the hand-off of 
the bus you accept all incoming MR, right? Or do you check all devices BCR?

Best regards,
Vitor Soares