Re: [PATCH 1/4] media: qcom: camss: Add PM clock support and integrate with runtime PM

Hi Bryan,

On Thu, Jul 30, 2026 at 10:39 AM Bryan O'Donoghue
<[email protected]> wrote:
>
> On 17/07/2026 15:20, Loic Poulain wrote:
> > Add optional PM clock support to the CAMSS driver using the PM clock
> > framework. This allows CAMSS clocks to be registered once and
> > automatically managed during runtime suspend and resume.
> >
> > This is especially useful for global CAMSS clocks that are shared across
> > multiple CAMSS subblocks.
> >
> > This avoids the need for each subblock to reference and manage the
> > shared clocks individually. A typical example is the set of clocks in
> > the top_group, which may be used by CSID, PHY, CCI, and other CAMSS
> > blocks.
> >
> > Introduce a small PM clock descriptor table in the CAMSS resources
> > structure to describe clocks and their optional rates. Initialize
> > these clocks at probe time and delegate clock ownership to the PM
> > core.
> >
> > Hook PM clock handling into the runtime PM callbacks to ensure clocks
> > are properly suspended and resumed alongside power domains and ICC
> > paths.
> >
> > Signed-off-by: Loic Poulain <[email protected]>
> > ---
> >   drivers/media/platform/qcom/camss/camss.c | 40 ++++++++++++++++++++++++++++++-
> >   drivers/media/platform/qcom/camss/camss.h |  1 +
> >   2 files changed, 40 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/media/platform/qcom/camss/camss.c b/drivers/media/platform/qcom/camss/camss.c
> > index 2123f6388e3d7eafe669efd6b033e22d8eb5cf79..6a2bf3373e8755805c8cd0f8fe5037b788d68fa2 100644
> > --- a/drivers/media/platform/qcom/camss/camss.c
> > +++ b/drivers/media/platform/qcom/camss/camss.c
> > @@ -18,6 +18,7 @@
> >   #include <linux/of_graph.h>
> >   #include <linux/pm_runtime.h>
> >   #include <linux/pm_domain.h>
> > +#include <linux/pm_clock.h>
> >   #include <linux/slab.h>
> >   #include <linux/videodev2.h>
> >
> > @@ -5346,6 +5347,35 @@ static void camss_genpd_cleanup(struct camss *camss)
> >       dev_pm_domain_detach(camss->genpd, true);
> >   }
> >
> > +/*
> > + * camss_init_pm_clks - register shared CAMSS clocks with the PM clock framework
> > + *
> > + * Clocks listed in res->pm_clks are shared across all CAMSS sub-devices (e.g.
> > + * top_ahb, axi). They are managed automatically by the PM framework.
> > + */
> > +static int camss_init_pm_clks(struct camss *camss)
> > +{
> > +     struct device *dev = camss->dev;
> > +     unsigned int i;
> > +     int ret;
> > +
> > +     if (!camss->res->pm_clks[0])
> > +             return 0;
> > +
> > +     ret = devm_pm_clk_create(dev);
> > +     if (ret)
> > +             return ret;
> > +
> > +     for (i = 0; i < CAMSS_RES_MAX && camss->res->pm_clks[i]; i++) {
> > +             ret = pm_clk_add(dev, camss->res->pm_clks[i]);
> > +             if (ret)
> > +                     dev_warn(dev, "failed to add pm_clk %s: %d\n",
> > +                              camss->res->pm_clks[i], ret);
> > +     }
> > +
> > +     return 0;
> > +}
> > +
> >   /*
> >    * camss_probe - Probe CAMSS platform device
> >    * @pdev: Pointer to CAMSS platform device
> > @@ -5434,6 +5464,10 @@ static int camss_probe(struct platform_device *pdev)
> >
> >       pm_runtime_enable(dev);
> >
> > +     ret = camss_init_pm_clks(camss);
> > +     if (ret)
> > +             goto err_v4l2_device_unregister;
> > +
> >       ret = camss_parse_ports(camss);
> >       if (ret < 0)
> >               goto err_v4l2_device_unregister;
> > @@ -5775,7 +5809,7 @@ static int __maybe_unused camss_runtime_suspend(struct device *dev)
> >                       return ret;
> >       }
> >
> > -     return 0;
> > +     return pm_clk_suspend(dev);
>    CC      drivers/media/platform/mediatek/vcodec/common/mtk_vcodec_dbgfs.o
>    CC      drivers/media/platform/mediatek/mdp3/mtk-mdp3-vpu.o
>    AR      drivers/staging/media/ipu7/built-in.a
> In file included from ./include/uapi/linux/posix_types.h:5,
>                   from ./include/uapi/linux/types.h:14,
>                   from ./include/linux/types.h:5,
>                   from ./include/linux/kasan-checks.h:5,
>                   from ./include/asm-generic/rwonce.h:26,
>                   from ./arch/x86/include/generated/asm/rwonce.h:1,
>                   from ./include/linux/compiler.h:369,
>                   from ./include/linux/err.h:5,
>                   from ./include/linux/clk.h:12,
>                   from drivers/media/platform/qcom/camss/camss.c:10:
> drivers/media/platform/qcom/camss/camss.c: In function
> ‘camss_runtime_suspend’:
> ./include/linux/stddef.h:8:14: error: called object is not a function or
> function pointer
>      8 | #define NULL ((void *)0)
>        |              ^
> ./include/linux/pm_clock.h:77:25: note: in expansion of macro ‘NULL’
>     77 | #define pm_clk_suspend  NULL
>        |                         ^~~~
> drivers/media/platform/qcom/camss/camss.c:5841:16: note: in expansion of
> macro ‘pm_clk_suspend’
>   5841 |         return pm_clk_suspend(dev);
>        |                ^~~~~~~~~~~~~~
> drivers/media/platform/qcom/camss/camss.c: In function
> ‘camss_runtime_resume’:
> ./include/linux/stddef.h:8:14: error: called object is not a function or
> function pointer
>      8 | #define NULL ((void *)0)
>        |              ^
> ./include/linux/pm_clock.h:78:25: note: in expansion of macro ‘NULL’
>     78 | #define pm_clk_resume   NULL
>        |                         ^~~~
> drivers/media/platform/qcom/camss/camss.c:5851:15: note: in expansion of
> macro ‘pm_clk_resume’
>   5851 |         ret = pm_clk_resume(dev);
>        |               ^~~~~~~~~~~~~
> make[7]: *** [scripts/Makefile.build:289:
> drivers/media/platform/qcom/camss/camss.o] Error 1
> make[7]: *** Waiting for unfinished jobs....
>    CC      drivers/media/usb/pwc/pwc-misc.o
>
> Please fix.

Thanks, I submitted a v3 with this fixed.

Regards,
Loic