linux-kernel - Re: [PATCH 1/2] remoteproc: imx

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Date:   Thu, 5 Mar 2020 11:36:19 -0700
From:   Mathieu Poirier <mathieu.poirier@...aro.org>
To:     nikita.shubin@...uefel.me
Cc:     Nikita Shubin <nshubin@...con.com>,
        Ohad Ben-Cohen <ohad@...ery.com>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Fabio Estevam <festevam@...il.com>,
        NXP Linux Team <linux-imx@....com>,
        linux-remoteproc <linux-remoteproc@...r.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] remoteproc: imx_rproc: dummy kick method

On Thu, 5 Mar 2020 at 11:07, <nikita.shubin@...uefel.me> wrote:
>
>
>
> 05.03.2020, 20:54, "Mathieu Poirier" <mathieu.poirier@...aro.org>:
> > On Thu, 5 Mar 2020 at 10:29, <nikita.shubin@...uefel.me> wrote:
> >>  05.03.2020, 19:17, "Mathieu Poirier" <mathieu.poirier@...aro.org>:
> >>  > On Wed, 4 Mar 2020 at 07:25, Nikita Shubin <NShubin@...con.com> wrote:
> >>  >> add kick method that does nothing, to avoid errors in rproc_virtio_notify.
> >>  >>
> >>  >> Signed-off-by: Nikita Shubin <NShubin@...con.com>
> >>  >> ---
> >>  >> drivers/remoteproc/imx_rproc.c | 6 ++++++
> >>  >> 1 file changed, 6 insertions(+)
> >>  >>
> >>  >> diff --git a/drivers/remoteproc/imx_rproc.c b/drivers/remoteproc/imx_rproc.c
> >>  >> index 3e72b6f38d4b..796b6b86550a 100644
> >>  >> --- a/drivers/remoteproc/imx_rproc.c
> >>  >> +++ b/drivers/remoteproc/imx_rproc.c
> >>  >> @@ -240,9 +240,15 @@ static void *imx_rproc_da_to_va(struct rproc *rproc, u64 da, int len)
> >>  >> return va;
> >>  >> }
> >>  >>
> >>  >> +static void imx_rproc_kick(struct rproc *rproc, int vqid)
> >>  >> +{
> >>  >> +
> >>  >> +}
> >>  >> +
> >>  >
> >>  > If rproc::kick() is empty, how does the MCU know there is packets to
> >>  > fetch in the virtio queues?
> >>
> >>  Well, of course it doesn't i understand this perfectly - just following documentation citing:
> >>
> >>  | Every remoteproc implementation should at least provide the ->start and ->stop
> >>  | handlers. If rpmsg/virtio functionality is also desired, then the ->kick handler
> >>  | should be provided as well.
> >>
> >>  But i as i mentioned in "remoteproc: Fix NULL pointer dereference in rproc_virtio_notify" kick method will be called if
> >>  "resource_table exists in firmware and has "Virtio device entry" defined" anyway, the imx_rproc is not in control of what
> >>  exactly it is booting, so such situation can occur.
> >
> > If I understand correctly, the MCU can boot images that have a virtio
> > device in its resource table and still do useful work even if the
> > virtio device/rpmsg bus can't be setup - is this correct?
>
> Yes, this assumption is correct.
>
> Despite this situation is not i desire at all - such thing can happen.
> I am currently using co-proc as a realtime part of UGV control,
> so it must immediately stop the engines, if not provided with navigational information.
>
> The imx7d MCU have access to the most periphery that have the main processor.
>
> Of course the kick method should do real work, but i decided to submit step by step if i am allowed to do so.

Ok, the situation is clearer now and I have put your patches back in
my queue.  I am seriously back-logged at this time so it will take a
little while before I get to them.

>
> >
> > Thanks,
> > Mathieu
> >
> >>  >
> >>  >> static const struct rproc_ops imx_rproc_ops = {
> >>  >> .start = imx_rproc_start,
> >>  >> .stop = imx_rproc_stop,
> >>  >> + .kick = imx_rproc_kick,
> >>  >> .da_to_va = imx_rproc_da_to_va,
> >>  >> };
> >>  >>
> >>  >> --
> >>  >> 2.24.1