linux-kernel - Re: [PATCH v4 2/2] mailbox: sprd: Add Spreadtrum mailbox driver

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Message-ID: <CADBw62oFTV3MPuFQSL0MWyYQWy9MuhL70w5HGHPPV1EXBd3KEQ@mail.gmail.com>
Date:   Wed, 13 May 2020 12:13:54 +0800
From:   Baolin Wang <baolin.wang7@...il.com>
To:     Jassi Brar <jassisinghbrar@...il.com>
Cc:     Rob Herring <robh+dt@...nel.org>, Orson Zhai <orsonzhai@...il.com>,
        Chunyan Zhang <zhang.lyra@...il.com>,
        Devicetree List <devicetree@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 2/2] mailbox: sprd: Add Spreadtrum mailbox driver

Hi Jassi,

On Thu, May 7, 2020 at 11:23 AM Baolin Wang <baolin.wang7@...il.com> wrote:
>
> Hi Jassi,
>
> On Thu, May 7, 2020 at 7:25 AM Jassi Brar <jassisinghbrar@...il.com> wrote:
> >
> > On Wed, May 6, 2020 at 8:29 AM Baolin Wang <baolin.wang7@...il.com> wrote:
> > >
> > > Hi Jassi,
> > >
> > > On Tue, Apr 28, 2020 at 11:10 AM Baolin Wang <baolin.wang7@...il.com> wrote:
> > > >
> > > > From: Baolin Wang <baolin.wang@...soc.com>
> > > >
> > > > The Spreadtrum mailbox controller supports 8 channels to communicate
> > > > with MCUs, and it contains 2 different parts: inbox and outbox, which
> > > > are used to send and receive messages by IRQ mode.
> > > >
> > > > Signed-off-by: Baolin Wang <baolin.wang@...soc.com>
> > > > Signed-off-by: Baolin Wang <baolin.wang7@...il.com>
> > > > ---
> > > > Changes from v3:
> > > >  - Save the id in mbox_chan.con_priv and remove the 'sprd_mbox_chan'
> > > >
> > > > Changes from v2:
> > > >  - None.
> > > >
> > > > Changes from v1:
> > > >  - None
> > >
> > > Gentle ping, do you have any other comments? Thanks.
> > >
> > Yea, I am still not sure about the error returned in send_data().  It
> > will either never hit or there will be no easy recovery from it. The
> > api expects the driver to tell it the last-tx was done only when it
> > can send the next message. (There may be case like sending depend on
> > remote, which can't be ensured before hand).
>
> Actually this is an unusual case, suppose the remote target did not
> fetch the message as soon as possile, which will cause the FIFO
> overflow, so in this case we  can not send messages to the remote
> target any more, otherwise messages will be lost. Thus we can return
> errors to users to indicate that something wrong with the remote
> target need to be checked.
>
> So this validation in send_data() is mostly for debugging for this
> abnormal case and we will not trigger this issue if the remote target
> works well. So I think it is useful to keep this validation in
> send_data(). Thanks.

Any comments? Thanks.

-- 
Baolin Wang