Re: [PATCH v4 6/6] firmware: qcom: scm: introduce keep_mdt_buf flag in PAS context

[Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>]

On 4/30/26 9:12 PM, Mukesh Ojha wrote:
> The PAS image initialization path always retains the metadata buffer
> when a valid qcom_scm_pas_context is provided, even if the caller does
> not require it. This implicit behavior leads to unclear buffer ownership
> and forces new users of qcom_mdt_pas_load() to manually release
> metadata, which is error‑ prone and incorrect.
> 
> Add a keep_mdt_buf flag to struct qcom_scm_pas_context to make metadata
> retention explicit.  Metadata buffers are now freed by default and are
> only preserved when this flag is set. qcom_q6v5_pas enables this during
> probe for contexts that require retained metadata for subsequent PAS
> operations, while existing callers continue to work unchanged.
> 
> Signed-off-by: Mukesh Ojha <mukesh.ojha@oss.qualcomm.com>
> ---

[...]

>  	ret = __qcom_scm_pas_init_image(pas_id, mdata_phys, &res);
> -	if (ret < 0 || !ctx) {
> +
> +	/*
> +	 * Some clients still pass the PAS context as NULL. Until all clients
> +	 * switch to qcom_mdt_pas_load() and provide a valid PAS context, check
> +	 * for NULL before dereferencing it.
> +	 *
> +	 * When a valid context is provided, metadata handling differs across
> +	 * clients. For example, modem clients pass metadata to TrustZone that
> +	 * must not be freed until the authentication and reset SMCs are
> +	 * invoked, as the buffers remain locked until then.
> +	 *
> +	 * Other clients free their metadata immediately after the PAS_INIT
> +	 * SMC call. Therefore, keep_mdt_buf should be set to true for modem
> +	 * clients and false for others.

You say this...

[...]

> --- a/drivers/remoteproc/qcom_q6v5_pas.c
> +++ b/drivers/remoteproc/qcom_q6v5_pas.c
> @@ -669,6 +669,7 @@ static int qcom_pas_alloc_memory_region(struct qcom_pas *pas)
>  		return PTR_ERR(pas->pas_ctx);
>  
>  	pas->pas_ctx->use_tzmem = rproc->has_iommu;
> +	pas->pas_ctx->keep_mdt_buf = true;
>  	if (!pas->dtb_pas_id)
>  		return 0;
>  
> @@ -688,6 +689,7 @@ static int qcom_pas_alloc_memory_region(struct qcom_pas *pas)
>  		return PTR_ERR(pas->dtb_pas_ctx);
>  
>  	pas->dtb_pas_ctx->use_tzmem = rproc->has_iommu;
> +	pas->dtb_pas_ctx->keep_mdt_buf = true;

And you set it globally for all PAS rprocs

Konrad