linux-kernel - Re: [PATCH] remoteproc: imx_rproc: replace devm_clk_get() with devm_clk_get

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Message-ID: <CANLsYky2OyrVLqm5JWOQaFhR3Fxt0d_p_HG4-F1o-Tnh=OP3dA@mail.gmail.com>
Date: Fri, 25 Apr 2025 09:45:32 -0600
From: Mathieu Poirier <mathieu.poirier@...aro.org>
To: Hiago De Franco <hiagofranco@...il.com>, Peng Fan <peng.fan@....com>, 
	"Peng Fan (OSS)" <peng.fan@....nxp.com>
Cc: daniel.baluta@....com, iuliana.prodan@....nxp.com, 
	linux-remoteproc@...r.kernel.org, Bjorn Andersson <andersson@...nel.org>, 
	Shawn Guo <shawnguo@...nel.org>, Sascha Hauer <s.hauer@...gutronix.de>, 
	Pengutronix Kernel Team <kernel@...gutronix.de>, Fabio Estevam <festevam@...il.com>, imx@...ts.linux.dev, 
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org, 
	Hiago De Franco <hiago.franco@...adex.com>
Subject: Re: [PATCH] remoteproc: imx_rproc: replace devm_clk_get() with devm_clk_get_optional()

On Wed, 23 Apr 2025 at 13:22, Hiago De Franco <hiagofranco@...il.com> wrote:
>
> Hi Mathieu,
>
> On Wed, Apr 23, 2025 at 11:14:17AM -0600, Mathieu Poirier wrote:
> > Good morning,
> >
> > On Wed, Apr 23, 2025 at 12:51:31PM -0300, Hiago De Franco wrote:
> > > From: Hiago De Franco <hiago.franco@...adex.com>
> > >
> > > The "clocks" device tree property is not mandatory, and if not provided
> > > Linux will shut down the remote processor power domain during boot if it
> > > is not present, even if it is running (e.g. it was started by U-Boot's
> > > bootaux command).
> >
> > If a clock is not present imx_rproc_probe() will fail, the clock will remain
> > unused and Linux will switch it off.  I think that is description of what is
> > happening.
> >
> > >
> > > Use the optional devm_clk_get instead.
> > >
> > > Signed-off-by: Hiago De Franco <hiago.franco@...adex.com>
> > > ---
> > >  drivers/remoteproc/imx_rproc.c | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/remoteproc/imx_rproc.c b/drivers/remoteproc/imx_rproc.c
> > > index 74299af1d7f1..45b5b23980ec 100644
> > > --- a/drivers/remoteproc/imx_rproc.c
> > > +++ b/drivers/remoteproc/imx_rproc.c
> > > @@ -1033,7 +1033,7 @@ static int imx_rproc_clk_enable(struct imx_rproc *priv)
> > >     if (dcfg->method == IMX_RPROC_NONE)
> > >             return 0;
> > >
> > > -   priv->clk = devm_clk_get(dev, NULL);
> > > +   priv->clk = devm_clk_get_optional(dev, NULL);
> >
> > If my understanding of the problem is correct (see above), I think the real fix
> > for this is to make the "clocks" property mandatory in the bindings.
>
> Thanks for the information, from my understanding this was coming from
> the power domain, I had a small discussion about this with Peng [1],
> where I was able to bisect the issue into a scu-pd commit. But I see
> your point for this commit, I can update the commit description.
>

If commit 4f6c9832613b breaks on your platform then it should be reverted.

> About the change itself, I was not able to find a defined clock to use
> into the device tree node for the i.MX8QXP/DX, maybe I am missing
> something? I saw some downstream device trees from NXP using a dummy
> clock, which I tested and it works, however this would not be the
> correct solution.
>

If we make the clock optional, what guarantees do we have that the
clock the M4 is sharing with other devices won't be switched off?  To
me a clock needs to be defined in the device tree and referenced in
the remote processor bindings.

Thanks,
Mathieu

> [1] https://lore.kernel.org/lkml/20250404141713.ac2ntcsjsf7epdfa@hiago-nb/
>
> Cheers,
> Hiago.
>
> >
> > Daniel and Iuliana, I'd like to have your opinions on this.
> >
> > Thanks,
> > Mathieu
> >
> > >     if (IS_ERR(priv->clk)) {
> > >             dev_err(dev, "Failed to get clock\n");
> > >             return PTR_ERR(priv->clk);
> > > --
> > > 2.39.5
> > >