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

[Ajay Kumar Nandam <ajay.nandam@oss.qualcomm.com>]

On 9/22/2026 6:00 PM, Mark Brown 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

Thanks Mark, fixed both in v6.

I added a mutex to serialize scm_regions[] / num_scm_regions updates in
q6apm_dai_scm_assign() and q6apm_dai_scm_unassign(), and changed the 
reserved-memory size diagnostic to use %pa

Thanks
Ajay Kumar Nandam