[alsa-devel] [PATCH 10/19] ASoC: Intel: add mrfld DSP registers

[Lars-Peter Clausen]

On 06/23/2014 06:27 AM, Vinod Koul wrote:
> On Sat, Jun 21, 2014 at 08:56:42AM +0200, Lars-Peter Clausen wrote:
>> On 06/21/2014 08:22 AM, Vinod Koul wrote:
>>> On Fri, Jun 20, 2014 at 02:33:19PM +0200, Lars-Peter Clausen wrote:
>>>> On 06/20/2014 01:32 PM, Vinod Koul wrote:
>>>>> On Fri, Jun 20, 2014 at 10:22:30AM +0200, Lars-Peter Clausen wrote:
>>>>>> On 06/13/2014 02:33 PM, Vinod Koul wrote:
>>>>>>> +unsigned int sst_soc_read(struct snd_soc_platform *platform,
>>>>>>> +			unsigned int reg)
>>>>>>> +{
>>>>>>> +	struct sst_data *drv = snd_soc_platform_get_drvdata(platform);
>>>>>>> +
>>>>>>> +	pr_debug("%s: reg[%d] = %#x\n", __func__, reg, drv->widget[reg]);
>>>>>>> +	BUG_ON(reg > (SST_NUM_WIDGETS - 1));
>>>>>>> +	return drv->widget[reg];
>>>>>>> +}
>>>>>>> +
>>>>>>> +int sst_soc_write(struct snd_soc_platform *platform,
>>>>>>> +		  unsigned int reg, unsigned int val)
>>>>>>> +{
>>>>>>> +	struct sst_data *drv = snd_soc_platform_get_drvdata(platform);
>>>>>>> +
>>>>>>> +	pr_debug("%s: reg[%d] = %#x\n", __func__, reg, val);
>>>>>>> +	BUG_ON(reg > (SST_NUM_WIDGETS - 1));
>>>>>>> +	drv->widget[reg] = val;
>>>>>>> +	return 0;
>>>>>>> +}
>>>>>>
>>>>>> These seem to be purely virtual registers, what is this about? The
>>>>>> DAPM core is able to handle widgets and controls without any
>>>>>> register backing just fine. There is no need to emulate virtual
>>>>>> registers.
>>>>> But we need to store the mixer configuration for sending IPCs to DSP. So virtual
>>>>> register file is very much required
>>>>
>>>> Hm, ok. But how does this work, when is the IPC triggered and why
>>>> can't the IPC be done from within the write function?
>>> Write can come at any time, even when DSP is inactive. Also we want to tell DSP
>>> about the paths which are active
>>>
>>> So most of IPCs are sent from DAPM widget handlers with exception of controls
>>> which are active. For those we send IPC during get/put handlers.
>>
>> This sounds very similar to the auto-mute controls that are
>> supported by the ASoC core. Auto-mute controls will update the value
>> in the put handler, but only if the widget it is attached to is
>> powered up. If the widget is not powered up the value is stored and
>> will be written once the widget powers up. Try to see if you can
>> adopt the auto-mute controls for your usecase. I think this should
>> allow to remove some of the parts from the driver that peek into
>> core internal data structures.
>
> Do you mean autodisable bit? Btw this seems to be used only in kcontrol creation
> and not in runtime. Actually I wont find using this feature if we have it :)
>

Auto-disable is also used at runtime. If the auto-disable bit in a control 
is set to 1, the control will have the behavior as described above.

- Lars