Re: [PATCH v2 3/3] remoteproc: imx_rproc: add power mode check for remote core attachment

[Hiago De Franco <hiagofranco@gmail.com>]

Hello,

On Thu, May 08, 2025 at 12:03:33PM +0200, Ulf Hansson wrote:
> On Wed, 7 May 2025 at 18:02, Hiago De Franco <hiagofranco@gmail.com> wrote:
> >
> > From: Hiago De Franco <hiago.franco@toradex.com>
> >
> > When the remote core is started before Linux boots (e.g., by the
> > bootloader), the driver currently is not able to attach because it only
> > checks for cores running in different partitions. If the core was kicked
> > by the bootloader, it is in the same partition as Linux and it is
> > already up and running.
> >
> > This adds power mode verification through the SCU interface, enabling
> > the driver to detect when the remote core is already running and
> > properly attach to it.
> >
> > Signed-off-by: Hiago De Franco <hiago.franco@toradex.com>
> > Suggested-by: Peng Fan <peng.fan@nxp.com>
> > ---
> > v2: Dropped unecessary include. Removed the imx_rproc_is_on function, as
> > suggested.
> > ---
> >  drivers/remoteproc/imx_rproc.c | 13 +++++++++++++
> >  1 file changed, 13 insertions(+)
> >
> > diff --git a/drivers/remoteproc/imx_rproc.c b/drivers/remoteproc/imx_rproc.c
> > index 627e57a88db2..9b6e9e41b7fc 100644
> > --- a/drivers/remoteproc/imx_rproc.c
> > +++ b/drivers/remoteproc/imx_rproc.c
> > @@ -949,6 +949,19 @@ static int imx_rproc_detect_mode(struct imx_rproc *priv)
> >                         if (of_property_read_u32(dev->of_node, "fsl,entry-address", &priv->entry))
> >                                 return -EINVAL;
> >
> > +                       /*
> > +                        * If remote core is already running (e.g. kicked by
> > +                        * the bootloader), attach to it.
> > +                        */
> > +                       ret = imx_sc_pm_get_resource_power_mode(priv->ipc_handle,
> > +                                                               priv->rsrc_id);
> > +                       if (ret < 0)
> > +                               dev_err(dev, "failed to get power resource %d mode, ret %d\n",
> > +                                       priv->rsrc_id, ret);
> > +
> > +                       if (ret == IMX_SC_PM_PW_MODE_ON)
> > +                               priv->rproc->state = RPROC_DETACHED;
> > +
> >                         return imx_rproc_attach_pd(priv);
> 
> Why is it important to potentially set "priv->rproc->state =
> RPROC_DETACHED" before calling imx_rproc_attach_pd()?
> 
> Would it be possible to do it the other way around? First calling
> imx_rproc_attach_pd() then get the power-mode to know if
> RPROC_DETACHED should be set or not?
> 
> The main reason why I ask, is because of how we handle the single PM
> domain case. In that case, the PM domain has already been attached
> (and powered-on) before we reach this point.

I am not sure if I understood correcly, let me know if I missed
something. From my understanding in this case it does not matter, since
the RPROC_DETACHED will only be a flag to trigger the attach callback
from rproc_validate(), when rproc_add() is called inside
remoteproc_core.c.

With that we can correcly attach to the remote core running, which was
not possible before, where the function returns at "return
imx_rproc_attach_pd(priv);" with the RPROC_OFFLINE state to
rproc_validate().

> 
> >                 }
> >
> > --
> > 2.39.5
> >
> 
> Kind regards
> Uffe

Best Regards,
Hiago.