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

[Ulf Hansson <ulf.hansson@linaro.org>]

On Fri, 9 May 2025 at 21:13, Hiago De Franco <hiagofranco@gmail.com> wrote:
>
> On Fri, May 09, 2025 at 12:37:02PM +0200, Ulf Hansson wrote:
> > On Thu, 8 May 2025 at 22:28, Hiago De Franco <hiagofranco@gmail.com> wrote:
> > >
> > > 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.
> >
> > Okay, I see.
> >
> > To me, it sounds like we should introduce a new genpd helper function
> > instead. Something along the lines of this (drivers/pmdomain/core.c)
> >
> > bool dev_pm_genpd_is_on(struct device *dev)
> > {
> >         struct generic_pm_domain *genpd;
> >         bool is_on;
> >
> >         genpd = dev_to_genpd_safe(dev);
> >         if (!genpd)
> >                 return false;
> >
> >         genpd_lock(genpd);
> >         is_on = genpd_status_on(genpd);
> >         genpd_unlock(genpd);
> >
> >         return is_on;
> > }
> >
> > After imx_rproc_attach_pd() has run, we have the devices that
> > correspond to the genpd(s). Those can then be passed as in-parameters
> > to the above function to get the power-state of their PM domains
> > (genpds). Based on that, we can decide if priv->rproc->state should be
> > to RPROC_DETACHED or not. Right?
>
> Got your idea, I think it should work yes, I am not so sure how. From
> what I can see these power domains are managed by
> drivers/pmdomain/imx/scu-pd.c and by enabling the debug messages I can
> see the power mode is correct when the remote core is powered on:
>
> [    0.317369] imx-scu-pd system-controller:power-controller: cm40-pid0 : IMX_SC_PM_PW_MODE_ON
>
> and powered off:
>
> [    0.314953] imx-scu-pd system-controller:power-controller: cm40-pid0 : IMX_SC_PM_PW_MODE_OFF
>
> But I cannot see how to integrate this into the dev_pm_genpd_is_on() you
> proposed. For a quick check, I added this function and it always return
> NULL at dev_to_genpd_safe(). Can you help me to understand this part?

As your device has multiple PM domains and those gets attached with
dev_pm_domain_attach_list(), the device(s) that you should use with
dev_pm_genpd_is_on() are in imx_rproc->pd_list->pd_devs[n].

>
> >
> > In this way we don't need to export unnecessary firmware functions
> > from firmware/imx/misc.c, as patch1/3 does.
> >
> > If you think it can work, I can help to cook a formal patch for the
> > above helper that you can fold into your series. Let me know.
> >
> > >
> > > 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().
> >
> > I see, thanks for clarifying!
> >
> > Kind regards
> > Uffe
>
> Thank you!
> Hiago.

Kind regards
Uffe