Re: [PATCH] ASoC: tas2783-sdw: power the Function up before preparing the port

[Mukunda,Vijendar]

On 13/08/26 18:52, Mark Brown wrote:
> On Thu, Aug 13, 2026 at 12:28:10AM +0300, Andrey Golovko wrote:
>
>> A Data Port cannot complete channel preparation while the SDCA Function
>> is powered down: the peripheral raises the channel's bit in
>> DPn_PrepareStatus and never clears it.
> ...
>
>> Power the Function up in the PRE_PREP callback, immediately before the
>> PrepareCtrl write it already performs, so that preparation has what it
>> needs on every path that prepares a port.
>>  	case SDW_OPS_PORT_PRE_PREP:
>> +		/*
>> +		 * The Function has to be powered before the port can complete
>> +		 * channel preparation.  hw_params() does that when a stream is
>> +		 * set up, but a stream that is only re-prepared - as userspace
>> +		 * does after the peripheral lost power in S0i3 - does not go
>> +		 * through hw_params() again, and the peripheral is back at its
>> +		 * PS3 reset default.  Power it up here, where it is needed.
>> +		 */
>> +		scoped_guard(mutex, &tas_dev->pde_lock)
>> +			ret = regmap_write(tas_dev->regmap,
>> +					   SDW_SDCA_CTL(1, TAS2783_SDCA_ENT_PDE23,
>> +							TAS2783_SDCA_CTL_REQ_POW_STATE, 0),
>> +					   TAS2783_SDCA_POW_STATE_ON);
>> +		if (ret) {
>> +			dev_err(dev, "power up failed for port %d, err=%d\n",
>> +				prep_ch->num, ret);
>> +			return ret;
>> +		}
> Does this DTRT if userspace restartss the stream by directly calling
> SNDRV_PCM_IOCTL_RESUME (AMD adverise SNDR_PCM_INFO_RESUME...)?
> Similarly we can suspend while prepared.  Either something needs to
> force us to prepare again or this needs to be moved somewhere that's
> always called.
I agree with Mark's observation. For drivers advertising SNDRV_PCM_INFO_RESUME,
userspace may resume a stream via SNDRV_PCM_IOCTL_RESUME without going through
a new prepare cycle. Similarly, a stream may be suspended while already
prepared and later resumed without re-running PRE_PREP.
If those paths do not guarantee port preparation is executed again, we either
need to force a re-prepare after power loss or move the power-up sequence to a
callback that is always hit before data transfer resumes.

>
>> +
>>  		ret = sdw_write_no_pm(slave, addr, prep_ch->ch_mask);
>>  		if (ret)
>>  			dev_err(dev, "prep failed for port %d, err=%d\n",
>>
>> base-commit: 6f6fb37f9f9a8ae88faa1b5b1978e57381488502
>> -- 
>> 2.53.0
>>