linux-kernel - Re: [PATCH v2 01/11] firmware: qcom_scm: Introduce PAS context initialization helper

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Message-ID: <3b74157a-3f2a-4533-acf6-7cab8154709c@quicinc.com>
Date: Tue, 19 Aug 2025 22:47:45 +0530
From: Pavan Kondeti <pavan.kondeti@....qualcomm.com>
To: Mukesh Ojha <mukesh.ojha@....qualcomm.com>
Cc: Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konradybcio@...nel.org>,
        Vikash Garodia <quic_vgarodia@...cinc.com>,
        Dikshita Agarwal <quic_dikshita@...cinc.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Abhinav Kumar <abhinav.kumar@...ux.dev>,
        Bryan O'Donoghue <bryan.odonoghue@...aro.org>,
        linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-media@...r.kernel.org, linux-remoteproc@...r.kernel.org
Subject: Re: [PATCH v2 01/11] firmware: qcom_scm: Introduce PAS context
 initialization helper

On Tue, Aug 19, 2025 at 10:24:36PM +0530, Mukesh Ojha wrote:
> Currently, remoteproc and non-remoteproc subsystems use different
> variants of the MDT loader helper API, primarily due to the handling of
> the metadata context. Remoteproc subsystems retain this context until
> authentication and reset, while non-remoteproc subsystems (e.g., video,
> graphics) do not require it.
> 
> Unify the metadata loading process for both remoteproc and
> non-remoteproc subsystems by introducing a dedicated PAS context
> initialization function.
> 
> By introducing qcom_scm_pas_ctx_init(), we can standardize the API usage
> across subsystems and reduce the number of parameters passed to MDT
> loader functions, improving code clarity and maintainability.
> 
> Signed-off-by: Mukesh Ojha <mukesh.ojha@....qualcomm.com>
> ---
>  drivers/firmware/qcom/qcom_scm.c       | 26 ++++++++++++++++++++++++++
>  include/linux/firmware/qcom/qcom_scm.h | 11 +++++++++++
>  2 files changed, 37 insertions(+)
> 
> diff --git a/drivers/firmware/qcom/qcom_scm.c b/drivers/firmware/qcom/qcom_scm.c
> index 96d5cf40a74c..33187d4f4aef 100644
> --- a/drivers/firmware/qcom/qcom_scm.c
> +++ b/drivers/firmware/qcom/qcom_scm.c
> @@ -558,6 +558,32 @@ static void qcom_scm_set_download_mode(u32 dload_mode)
>  		dev_err(__scm->dev, "failed to set download mode: %d\n", ret);
>  }
>  
> +void *qcom_scm_pas_ctx_init(struct device *dev, u32 peripheral, phys_addr_t mem_phys,
> +			    size_t mem_size, bool save_mdt_ctx)

Since we export this for other drivers/module, consider adding kerneldoc
comments.

> +{
> +	struct qcom_scm_pas_ctx *ctx;
> +
> +	ctx = devm_kzalloc(dev, sizeof(*ctx), GFP_KERNEL);
> +	if (!ctx)
> +		return NULL;
> +
> +	ctx->dev = dev;
> +	ctx->peripheral = peripheral;
> +	ctx->mem_phys = mem_phys;
> +	ctx->mem_size = mem_size;
> +	ctx->save_mdt_ctx = save_mdt_ctx;
> +	ctx->metadata = NULL;

This seems unnecessary.

> +
> +	if (save_mdt_ctx) {
> +		ctx->metadata = devm_kzalloc(dev, sizeof(*ctx->metadata), GFP_KERNEL);
> +		if (!ctx->metadata)
> +			return NULL;

Do we really need to pass this burden to the caller to pass save_mdt_ctx
as true/false? What happens if we always keep metadata in qcom_scm_pas_ctx struct
and let clients use it if needed.

> +	}
> +
> +	return ctx;
> +}
> +EXPORT_SYMBOL_GPL(qcom_scm_pas_ctx_init);

Is there an equivalant ctx_destroy() function? It would be confusing for
drivers to call this in their probe and not doing anything upon error or
in their bus::remove callbacks. I don't know if we really want to
convert the whole function under devres or just provide a destroy
callback.

> +
>  /**
>   * qcom_scm_pas_init_image() - Initialize peripheral authentication service
>   *			       state machine for a given peripheral, using the
> diff --git a/include/linux/firmware/qcom/qcom_scm.h b/include/linux/firmware/qcom/qcom_scm.h
> index a55ca771286b..b7eb206561a9 100644
> --- a/include/linux/firmware/qcom/qcom_scm.h
> +++ b/include/linux/firmware/qcom/qcom_scm.h
> @@ -72,6 +72,17 @@ struct qcom_scm_pas_metadata {
>  	ssize_t size;
>  };
>  
> +struct qcom_scm_pas_ctx {
> +	struct device *dev;
> +	u32 peripheral;
> +	phys_addr_t mem_phys;
> +	size_t mem_size;
> +	struct qcom_scm_pas_metadata *metadata;
> +	bool save_mdt_ctx;

As mentioned above, can we just include qcom_scm_pas_metadata struct all
the time?

Thanks,
Pavan