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

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Message-ID: <a904d953-acb2-44f6-81bd-118f7abd22da@nvidia.com>
Date: Wed, 3 Sep 2025 13:33:44 +0100
From: Jon Hunter <jonathanh@...dia.com>
To: Ulf Hansson <ulf.hansson@...aro.org>
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

Hi Ulf,

On 11/08/2025 13:11, Ulf Hansson wrote:
> 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?

Sorry for the delay, I was on vacation. Yes makes sense and drivers for 
some of the above drivers are not yet upstreamed to mainline and so this 
would be expected for now.

Thanks
Jon

-- 
nvpublic