linux-kernel - Re: [REGRESSION] Kernel reboots unexpectdely on i.MX8X when Cortex-M4 is running and it was started by U-Boot bootaux

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Message-ID: <20250415184009.2fvtn7tbe6uzwiyg@hiago-nb>
Date: Tue, 15 Apr 2025 15:40:09 -0300
From: Hiago De Franco <hiagofranco@...il.com>
To: Peng Fan <peng.fan@....com>
Cc: "linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	Ulf Hansson <ulf.hansson@...aro.org>,
	Shawn Guo <shawnguo@...nel.org>,
	Sascha Hauer <s.hauer@...gutronix.de>,
	"linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"regressions@...ts.linux.dev" <regressions@...ts.linux.dev>,
	Hiago De Franco <hiago.franco@...adex.com>
Subject: Re: [REGRESSION] Kernel reboots unexpectdely on i.MX8X when
 Cortex-M4 is running and it was started by U-Boot bootaux

On Tue, Apr 15, 2025 at 12:11:33AM +0000, Peng Fan wrote:
> > Subject: Re: [REGRESSION] Kernel reboots unexpectdely on i.MX8X
> > when Cortex-M4 is running and it was started by U-Boot bootaux
> > 
> > Hi Peng,
> > 
> > On Mon, Apr 14, 2025 at 06:09:49AM +0000, Peng Fan wrote:
> > >
> > > In your case, m4 is in same scu partition as a53, so m4 power domain
> > > is manageable(owned) by Linux.
> > >
> > > However to m4 earlyboot(kicked by bootloader), if you not wanna
> > linux
> > > to handle m4, use scu_rm to create a separate partition in u-boot.
> > > If you wanna linux to handle m4, but not wanna linux to shutdown
> > the
> > > pd in kernel boot, imx_rproc.c needs to be built in, and need to add a
> > > clock entry or use clock optional api in imx_rproc.c .
> > >
> > > Current imx_rproc.c needs a clock entry to probe pass.
> > >
> > > I think in your case, this driver not probe pass, so the
> > > M4 pd still get powered off.
> > 
> > This was correct, indeed. I was not able to find exactly where the
> > cortex-m4 clock is defined, so I added a clk_dummy to the imx8x-cm4
> > remoteproc node and now it works, the code continues to run and I
> > can control the m4 with Linux. Thanks!
> > 
> > One thing that I noticed is I cannot make the RPMsg work with this
> > devicetree node, even tought I assigned the correct memory-regions
> > (vdev0buffer, vdev0ring0...). Also tested with the rpmsg-lite from the
> > linux-imx. Is this supposed to work with RPMsg as well?
> 
> To make rpmsg work, you need a m4 demo that could publish
> resource table, such as i.MX tty echo or pingpong demo.
> 
> There is downstream rpmsg driver under drivers/rpmsg/imx_*.c
> that could be used to talk with m4.
> 
> helloworld demo does not have any virtio devices, so no rpmsg.

Got it, I was able to make it work with the downstream pingpong driver
and the MCUXpresso demo. I can launch the firmware using the remoteproc
and exchange data between the two cores.

There is something I noticed, when I start the pingpong demo with
U-Boot, it does not work. I run the pingpong modprobe on Linux but the
name service is never annouced. It only works if I start with the
remoteproc on Linux, not U-Boot. Is this because of Linux not being able
to control the M4?

If I start the binary using U-Boot, the "state" always report as
"offline" by the remoteproc driver.

> 
> Regards,
> Peng.
> 
> > 
> > >
> > >
> > > Regards,
> > > Peng.
> > >
> > 
> > Hiago

Thanks,
Hiago.