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

[Bryan O'Donoghue]

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 <loic.poulain@xxxxxxxxxxxxxxxx>
> ---
>   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 ret;

---
bod