linux-kernel - Re: [RFC PATCH] remoteproc: k3-r5: Fix check performed in k3_r5_rproc_{mbox

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Message-ID: <CANLsYky1Oxu7Fc1-gz53cR+KpO67nDE5LQGj_NV+czOwY2_2CA@mail.gmail.com>
Date: Tue, 17 Sep 2024 02:37:05 -0600
From: Mathieu Poirier <mathieu.poirier@...aro.org>
To: "Kumar, Udit" <u-kumar1@...com>
Cc: Siddharth Vadapalli <s-vadapalli@...com>, Hari Nagalla <hnagalla@...com>, Andrew Davis <afd@...com>, 
	andersson@...nel.org, b-padhi@...com, linux-remoteproc@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, 
	srk@...com
Subject: Re: [RFC PATCH] remoteproc: k3-r5: Fix check performed in k3_r5_rproc_{mbox_callback/kick}

On Mon, 16 Sept 2024 at 23:20, Kumar, Udit <u-kumar1@...com> wrote:
>
> On 9/16/2024 8:50 PM, Mathieu Poirier wrote:
> > On Mon, 16 Sept 2024 at 02:31, Siddharth Vadapalli <s-vadapalli@...com> wrote:
> >> Commit f3f11cfe8907 ("remoteproc: k3-r5: Acquire mailbox handle during
> >> probe routine") introduced a check in the "k3_r5_rproc_mbox_callback()" and
> >> "k3_r5_rproc_kick()" callbacks, causing them to exit if the remote core's
> >> state is "RPROC_DETACHED". However, the "__rproc_attach()" function that is
> >> responsible for attaching to a remote core, updates the state of the remote
> >> core to "RPROC_ATTACHED" only after invoking "rproc_start_subdevices()".
> >>
> >> The "rproc_start_subdevices()" function triggers the probe of the Virtio
> >> RPMsg devices associated with the remote core, which require that the
> >> "k3_r5_rproc_kick()" and "k3_r5_rproc_mbox_callback()" callbacks are
> >> functional. Hence, drop the check in the callbacks.
> > Honestly, I am very tempted to just revert f3f11cfe8907 and ea1d6fb5b571.
>
>
> Please don't :) , it will break rproc in general for k3 devices.
>

Why not - it is already broken anyway.  Reverting the patches will
force TI to actually think about the feature in terms of design,
completeness and testing.  The merge window opened on Sunday - I'm not
going to merge whack-a-mole patches and hope the right fix comes
along.

> Couple of solutions for this race around condition (in mine preference
> order)
>

This is for the TI team to discuss _and_ test thoroughly.  From hereon
and until I see things improve, all patches from TI will need to be
tagged with R-B and T-B tags (collected on the mailing lists) from two
different individuals before I look at them.

> 1) In
> https://elixir.bootlin.com/linux/v6.11/source/drivers/remoteproc/ti_k3_r5_remoteproc.c#L190
> have a check , if probe in is progress or not
>
> 2)
> https://elixir.bootlin.com/linux/v6.11/source/drivers/remoteproc/ti_k3_r5_remoteproc.c#L1205
> -- correct the state to ON or something else
>
> 3) Move condition
> https://elixir.bootlin.com/linux/v6.11/source/drivers/remoteproc/remoteproc_core.c#L1360
> before rproc_start_subdevices
> <https://elixir.bootlin.com/linux/v6.11/C/ident/rproc_start_subdevices>
> calling
>
>
>
> >
> >> Fixes: f3f11cfe8907 ("remoteproc: k3-r5: Acquire mailbox handle during probe routine")
> >> Signed-off-by: Siddharth Vadapalli <s-vadapalli@...com>
> >> ---
> >>
> >> Hello,
> >>
> >> Since the commit being fixed is not yet a part of Mainline Linux, this
> >> patch is based on linux-next tagged next-20240913.
> >>
> >> An alternative to this patch will be a change to the "__rproc_attach()"
> >> function in the "remoteproc_core.c" driver with
> >> rproc->state = RPROC_ATTACHED;
> >> being set after "rproc_attach_device()" is invoked, but __before__
> >> invoking "rproc_start_subdevices()". Since this change will be performed
> >> in the common Remoteproc Core, it appeared to me that fixing it in the
> >> TI remoteproc driver is the correct approach.
> >>
> >> The equivalent of this patch for ti_k3_dsp_remoteproc.c might also be
> >> required, which I shall post if the current patch is acceptable.
> >>
> >> Kindly review and share your feedback on this patch.
> >>
> >> Regards,
> >> Siddharth.
> >>
> >>   drivers/remoteproc/ti_k3_r5_remoteproc.c | 8 --------
> >>   1 file changed, 8 deletions(-)
> >>
> >> diff --git a/drivers/remoteproc/ti_k3_r5_remoteproc.c b/drivers/remoteproc/ti_k3_r5_remoteproc.c
> >> index 747ee467da88..4894461aa65f 100644
> >> --- a/drivers/remoteproc/ti_k3_r5_remoteproc.c
> >> +++ b/drivers/remoteproc/ti_k3_r5_remoteproc.c
> >> @@ -194,10 +194,6 @@ static void k3_r5_rproc_mbox_callback(struct mbox_client *client, void *data)
> >>          const char *name = kproc->rproc->name;
> >>          u32 msg = omap_mbox_message(data);
> >>
> >> -       /* Do not forward message from a detached core */
> >> -       if (kproc->rproc->state == RPROC_DETACHED)
> >> -               return;
> >> -
> >>          dev_dbg(dev, "mbox msg: 0x%x\n", msg);
> >>
> >>          switch (msg) {
> >> @@ -233,10 +229,6 @@ static void k3_r5_rproc_kick(struct rproc *rproc, int vqid)
> >>          mbox_msg_t msg = (mbox_msg_t)vqid;
> >>          int ret;
> >>
> >> -       /* Do not forward message to a detached core */
> >> -       if (kproc->rproc->state == RPROC_DETACHED)
> >> -               return;
> >> -
> >>          /* send the index of the triggered virtqueue in the mailbox payload */
> >>          ret = mbox_send_message(kproc->mbox, (void *)msg);
> >>          if (ret < 0)
> >> --
> >> 2.40.1
> >>