Re: [PATCH V2 0/2] remoteproc: imx: add start up delay

[Mathieu Poirier <mathieu.poirier@linaro.org>]

On Thu, Nov 03, 2022 at 05:08:15AM +0000, Peng Fan wrote:
> > Subject: Re: [PATCH V2 0/2] remoteproc: imx: add start up delay
> > 
> > On Wed, 2 Nov 2022 at 05:23, Peng Fan (OSS) <peng.fan@oss.nxp.com>
> > wrote:
> > >
> > > From: Peng Fan <peng.fan@nxp.com>
> > >
> > > V2:
> > >  Rebased on linux-next
> > >
> > > V1:
> > >
> > >
> > https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Flore
> > > .kernel.org%2Flkml%2F20220609123500.3492475-1-
> > peng.fan%40oss.nxp.com%2
> > >
> > F&amp;data=05%7C01%7Cpeng.fan%40nxp.com%7Cf14584bdef9349e744ca
> > 08dabcf7
> > >
> > e1be%7C686ea1d3bc2b4c6fa92cd99c5c301635%7C0%7C0%7C63803007007
> > 2451509%7
> > >
> > CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJ
> > BTiI6Ik1
> > >
> > haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&amp;sdata=Ck73gkOPpNVT
> > kcZL8olCZP8B
> > > %2BrIpZHV48uZBl2R8HdM%3D&amp;reserved=0
> > >
> > > There is case that after remoteproc start remote processor[M4], the M4
> > > runs slow and before M4 finish its own rpmsg framework initialization,
> > > linux sends out vring kick message, then M4 firmware drops the kick
> > > message. Some NXP released Cortex-M[x] images has such limitation that
> > > it requires linux sends out vring kick message after M4 firmware
> > > finish its rpmsg framework initialization.
> > >
> > > The best case is to use a method to let M4 notify Linux that M4 has
> > > finished initialization, but we could not patch released firmware,
> > > then update driver to detect notification.
> > >
> > > So add delay before linux send out vring kick message. It is not good
> > > to use a fixed time delay in driver, so I choose to get that from
> > > device tree.
> > >
> > 
> > From where I stand this is a hack to hide the lack of motivation to enact the
> > real solution that is outlined above.  I also wonder how these problems
> > were not caught during the testing phase.  Either find a way to upgrade your
> > firmware or keep this in your internal tree.
> In the beginning, i.mx not migrated to use remoteproc, i.MX release only support
> uboot kick Cortex-M core and use downstream imx_rpmsg driver to
> communicate with remote core. There is no runtime stop/start.
> 
> After migrated to remoteproc, we do see some issue, but old firmware was
> there.

You could also attach() to that remote processor, if the HW supports it.  But my
position remains the same - either find a way to work with this situation that
is not a hack or keep this patch in your internal tree.

> 
> Thanks,
> Peng.
> 
> > 
> > > Peng Fan (2):
> > >   dt-bindings: remoteproc: imx_rproc: add fsl,startup-delay-ms
> > >   remoteproc: imx_rproc: delay after kick remote processor
> > >
> > >  .../devicetree/bindings/remoteproc/fsl,imx-rproc.yaml    | 4 ++++
> > >  drivers/remoteproc/imx_rproc.c                           | 9 +++++++++
> > >  2 files changed, 13 insertions(+)
> > >
> > > --
> > > 2.37.1
> > >