linux-kernel - Re: [PATCH v3 20/24] pmdomain: core: Default to use of_genpd_sync

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Message-ID: <CAPDyKFqSyP3e=JRFYEuFefWVN5SYJWULU8SKzXmrThvyiVGXgg@mail.gmail.com>
Date: Mon, 11 Aug 2025 14:11:02 +0200
From: Ulf Hansson <ulf.hansson@...aro.org>
To: Jon Hunter <jonathanh@...dia.com>
Cc: Saravana Kannan <saravanak@...gle.com>, Stephen Boyd <sboyd@...nel.org>, linux-pm@...r.kernel.org, 
	"Rafael J . Wysocki" <rafael@...nel.org>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
	Michael Grzeschik <m.grzeschik@...gutronix.de>, Bjorn Andersson <andersson@...nel.org>, 
	Abel Vesa <abel.vesa@...aro.org>, Peng Fan <peng.fan@....nxp.com>, 
	Tomi Valkeinen <tomi.valkeinen@...asonboard.com>, Johan Hovold <johan@...nel.org>, 
	Maulik Shah <maulik.shah@....qualcomm.com>, Michal Simek <michal.simek@....com>, 
	Konrad Dybcio <konradybcio@...nel.org>, Thierry Reding <thierry.reding@...il.com>, 
	Hiago De Franco <hiago.franco@...adex.com>, Geert Uytterhoeven <geert@...ux-m68k.org>, 
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org, 
	"linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>
Subject: Re: [PATCH v3 20/24] pmdomain: core: Default to use
 of_genpd_sync_state() for genpd providers

On Thu, 31 Jul 2025 at 17:07, Jon Hunter <jonathanh@...dia.com> wrote:
>
> Hi Ulf,
>
> On 01/07/2025 12:47, Ulf Hansson wrote:
> > Unless the typical platform driver that act as genpd provider, has its own
> > ->sync_state() callback implemented let's default to use
> > of_genpd_sync_state().
> >
> > More precisely, while adding a genpd OF provider let's assign the
> > ->sync_state() callback, in case the fwnode has a device and its driver
> > doesn't have the ->sync_state() set already. In this way the typical
> > platform driver doesn't need to assign ->sync_state(), unless it has some
> > additional things to manage beyond genpds.
> >
> > Suggested-by: Saravana Kannan <saravanak@...gle.com>
> > Tested-by: Hiago De Franco <hiago.franco@...adex.com> # Colibri iMX8X
> > Tested-by: Tomi Valkeinen <tomi.valkeinen@...asonboard.com> # TI AM62A,Xilinx ZynqMP ZCU106
> > Signed-off-by: Ulf Hansson <ulf.hansson@...aro.org>
> > ---
> >   drivers/pmdomain/core.c | 9 +++++++++
> >   1 file changed, 9 insertions(+)
> >
> > diff --git a/drivers/pmdomain/core.c b/drivers/pmdomain/core.c
> > index ca47f91b9e91..5cef6de60c72 100644
> > --- a/drivers/pmdomain/core.c
> > +++ b/drivers/pmdomain/core.c
> > @@ -2600,6 +2600,11 @@ static bool genpd_present(const struct generic_pm_domain *genpd)
> >       return ret;
> >   }
> >
> > +static void genpd_sync_state(struct device *dev)
> > +{
> > +     return of_genpd_sync_state(dev->of_node);
> > +}
> > +
> >   /**
> >    * of_genpd_add_provider_simple() - Register a simple PM domain provider
> >    * @np: Device node pointer associated with the PM domain provider.
> > @@ -2628,6 +2633,8 @@ int of_genpd_add_provider_simple(struct device_node *np,
> >       if (!dev && !genpd_is_no_sync_state(genpd)) {
> >               genpd->sync_state = GENPD_SYNC_STATE_SIMPLE;
> >               device_set_node(&genpd->dev, fwnode);
> > +     } else {
> > +             dev_set_drv_sync_state(dev, genpd_sync_state);
> >       }
> >
> >       put_device(dev);
> > @@ -2700,6 +2707,8 @@ int of_genpd_add_provider_onecell(struct device_node *np,
> >       dev = get_dev_from_fwnode(fwnode);
> >       if (!dev)
> >               sync_state = true;
> > +     else
> > +             dev_set_drv_sync_state(dev, genpd_sync_state);
> >
> >       put_device(dev);
> >
>
> Following this change I am seeing the following warning on our Tegra194
> devices ...
>
>   WARNING KERN tegra-bpmp bpmp: sync_state() pending due to 17000000.gpu
>   WARNING KERN tegra-bpmp bpmp: sync_state() pending due to 3960000.cec
>   WARNING KERN tegra-bpmp bpmp: sync_state() pending due to 15380000.nvjpg
>   WARNING KERN tegra-bpmp bpmp: sync_state() pending due to 154c0000.nvenc
>   WARNING KERN tegra-bpmp bpmp: sync_state() pending due to 15a80000.nvenc
>
> Per your change [0], the 'GENPD_FLAG_NO_SYNC_STATE' is set for Tegra
> and so should Tegra be using of_genpd_sync_state() by default?

This is a different power-domain provider (bpmp) in
drivers/firmware/tegra/bpmp.c and
drivers/pmdomain/tegra/powergate-bpmp.c.

For the bpmp we don't need GENPD_FLAG_NO_SYNC_STATE, as the
power-domain provider is described along with the
"nvidia,tegra186-bpmp" compatible string. In the other case
(drivers/soc/tegra/pmc.c) the "core-domain" and "powergates" are
described through child-nodes, while ->sync_state() is managed by the
parent-device-node.

In the bpmp case there is no ->sync_state() callback assigned, which
means genpd decides to assign a default one.

The reason for the warnings above is because we are still waiting for
those devices to be probed, hence the ->sync_state() callback is still
waiting to be invoked. Enforcing ->sync_state() callback to be invoked
can be done via user-space if that is needed.

Did that make sense?

>
> Thanks
> Jon
>
> [0] https://lore.kernel.org/all/20250701114733.636510-10-ulf.hansson@linaro.org/
> --
> nvpublic
>

Kind regards
Uffe