RE: [PATCH 1/1] remoteproc: fix recovery procedure

[Loic PALLARDY <loic.pallardy@st.com>]

Hi Xiang,

> -----Original Message-----
> From: xiang xiao <xiaoxiang781216@gmail.com>
> Sent: samedi 12 janvier 2019 19:29
> To: Loic PALLARDY <loic.pallardy@st.com>
> Cc: bjorn.andersson@linaro.org; ohad@wizery.com; linux-
> remoteproc@vger.kernel.org; linux-kernel@vger.kernel.org; Arnaud
> POULIQUEN <arnaud.pouliquen@st.com>; benjamin.gaignard@linaro.org; s-
> anna@ti.com
> Subject: Re: [PATCH 1/1] remoteproc: fix recovery procedure
> 
> Hi Loic,
> The change just hide the problem, I think. The big issue is:
> 1.virtio devices aren't destroyed by rpproc_stop
Virtio devices are destroyed by rproc_stop() as vdev is registered as rproc sub device.
rproc_stop() is calling rproc_stop_subdevices() which is in charge of removing virtio device and associated children.
rproc_vdev_do_stop() --> rproc_remove_virtio_dev() --> unregister_virtio_device()

Please find below trace of a recovery on my ST SOC. My 2 rpmsg tty are removed and re-inserted correctly
root@stm32mp1:~# ls /dev/ttyRPMSG*
/dev/ttyRPMSG0  /dev/ttyRPMSG1
root@stm32mp1:~# [  154.832523] remoteproc remoteproc0: crash detected in m4: type watchdog
[  154.837725] remoteproc remoteproc0: handling crash #2 in m4
[  154.843319] remoteproc remoteproc0: recovering m4
[  154.849185] rpmsg_tty virtio0.rpmsg-tty-channel.-1.0: rpmsg tty device 0 is removed
[  154.857572] rpmsg_tty virtio0.rpmsg-tty-channel.-1.1: rpmsg tty device 1 is removed
[  155.382327] remoteproc remoteproc0: warning: remote FW shutdown without ack
[  155.387857] remoteproc remoteproc0: stopped remote processor m4
[  155.398988]  m4@0#vdev0buffer: assigned reserved memory node vdev0buffer@10044000
[  155.405910] virtio_rpmsg_bus virtio0: creating channel rpmsg-tty-channel addr 0x0
[  155.413422] rpmsg_tty virtio0.rpmsg-tty-channel.-1.0: new channel: 0x400 -> 0x0 : ttyRPMSG0
[  155.421038] virtio_rpmsg_bus virtio0: creating channel rpmsg-tty-channel addr 0x1
[  155.429088] rpmsg_tty virtio0.rpmsg-tty-channel.-1.1: new channel: 0x401 -> 0x1 : ttyRPMSG1
[  155.437338] virtio_rpmsg_bus virtio0: rpmsg host is online
[  155.442401]  m4@0#vdev0buffer: registered virtio0 (type 7)
[  155.461154] remoteproc remoteproc0: remote processor m4 is now up
ls /dev/ttyRPMSG*
/dev/ttyRPMSG0  /dev/ttyRPMSG1
root@stm32mp1:~#

As vdev is including in a larger struct allocated by rproc, it is safe to set it to 0 before initializing virtio device while rproc subdevice sequence is respected.

> 2.and then rpmsg child devices aren't destroyed too
> Then, when the remote start and create rpmsg channel again, the
> duplicated channel will appear in kernel.
> To fix this problem, we need go through rpproc_shutdown/rproc_boot to
> destroy all devices(virtio and rpmsg) and create them again.
Rproc_shutdown/rproc_boot is solving the issue too, except if rproc_boot() was called several times and so rproc->power atomic not equal to 1.
Using only rproc_stop() and rproc_start() allows to preserve rproc->power and so to be silent from rproc user pov.

Regards,
Loic
> 
> Thanks
> Xiang
> 
> On Wed, Jan 9, 2019 at 6:56 PM Loic Pallardy <loic.pallardy@st.com> wrote:
> >
> > Commit 7e83cab824a87e83cab824a8 ("remoteproc: Modify recovery path
> > to use rproc_{start,stop}()") replaces rproc_{shutdown,boot}() with
> > rproc_{stop,start}(), which skips destroy the virtio device at stop
> > but re-initializes it again at start.
> >
> > Issue is that struct virtio_dev is not correctly reinitialized like done
> > at initial allocation thanks to kzalloc() and kobject is considered as
> > already initialized by kernel. That is due to the fact struct virtio_dev
> > is allocated and released at vdev resource handling level managed and
> > virtio device is registered and unregistered at rproc subdevices level.
> >
> > This patch initializes struct virtio_dev to 0 before using it and
> > registering it.
> >
> > Fixes: 7e83cab824a8 ("remoteproc: Modify recovery path to use
> rproc_{start,stop}()")
> >
> > Reported-by: Xiang Xiao <xiaoxiang781216@gmail.com>
> > Signed-off-by: Loic Pallardy <loic.pallardy@st.com>
> > ---
> >  drivers/remoteproc/remoteproc_virtio.c | 2 ++
> >  1 file changed, 2 insertions(+)
> >
> > diff --git a/drivers/remoteproc/remoteproc_virtio.c
> b/drivers/remoteproc/remoteproc_virtio.c
> > index 183fc42a510a..88eade99395c 100644
> > --- a/drivers/remoteproc/remoteproc_virtio.c
> > +++ b/drivers/remoteproc/remoteproc_virtio.c
> > @@ -332,6 +332,8 @@ int rproc_add_virtio_dev(struct rproc_vdev *rvdev,
> int id)
> >         struct virtio_device *vdev = &rvdev->vdev;
> >         int ret;
> >
> > +       /* Reset vdev struct as you don't know how it has been previously
> used */
> > +       memset(vdev, 0, sizeof(struct virtio_device));
> >         vdev->id.device = id,
> >         vdev->config = &rproc_virtio_config_ops,
> >         vdev->dev.parent = dev;
> > --
> > 2.7.4
> >