Re: [PATCH v5 4/4] ASoC: qcom: q6apm-dai: add SCM buffer assignment for mDSP platforms

[Mark Brown <broonie@kernel.org>]

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On Tue, Sep 22, 2026 at 12:38:12AM +0530, Ajay Kumar Nandam wrote:
> On platforms such as Qualcomm Shikra, audio is served by the modem DSP
> (mDSP) which runs in a stage-2 protected context. Unlike ADSP targets
> where SMMU-mapped system RAM is directly accessible, the mDSP cannot
> reach the PCM buffers unless they are explicitly SCM-assigned to the
> appropriate Virtual Machine IDs (VMIDs). Without this assignment, audio
> does not function on these platforms.

> +static int q6apm_dai_scm_assign(struct q6apm_dai_data *pdata,
> +				phys_addr_t addr, size_t size)
> +{

> +	r = &pdata->scm_regions[pdata->num_scm_regions++];

This needs a lock.

> @@ -1021,6 +1168,7 @@ static int q6apm_dai_probe(struct platform_device *pdev)
>  {

> +			if (per_stream <= POS_BUFFER_BYTES + PAGE_SIZE) {
> +				dev_err(dev,
> +					"reserved-memory pool too small: %llu bytes\n",
> +					(u64)rmem->size);

%pa

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