[alsa-devel] [PATCH] ASoC: DAPM: Add support for multi register mux

[Lars-Peter Clausen]

On 04/02/2014 08:56 AM, Songhee Baek wrote:
>
>
>> -----Original Message-----
>> From: Lars-Peter Clausen [mailto:lars at metafoo.de]
>> Sent: Tuesday, April 01, 2014 11:47 PM
>> To: Songhee Baek
>> Cc: Arun Shamanna Lakshmi; lgirdwood at gmail.com; broonie at kernel.org;
>> swarren at wwwdotorg.org; perex at perex.cz; tiwai at suse.de; alsa-
>> devel at alsa-project.org; linux-kernel at vger.kernel.org
>> Subject: Re: [PATCH] ASoC: DAPM: Add support for multi register mux
>>
>> On 04/02/2014 08:17 AM, Songhee Baek wrote:
>>>> -----Original Message-----
>>>> From: Lars-Peter Clausen [mailto:lars at metafoo.de]
>>>> Sent: Tuesday, April 01, 2014 11:00 PM
>>>> To: Arun Shamanna Lakshmi
>>>> Cc: lgirdwood at gmail.com; broonie at kernel.org;
>> swarren at wwwdotorg.org;
>>>> perex at perex.cz; tiwai at suse.de; alsa-devel at alsa-project.org; linux-
>>>> kernel at vger.kernel.org; Songhee Baek
>>>> Subject: Re: [PATCH] ASoC: DAPM: Add support for multi register mux
>>>>
>>>> On 04/01/2014 08:26 PM, Arun Shamanna Lakshmi wrote:
>>>> [...]
>>>>>>> diff --git a/sound/soc/soc-dapm.c b/sound/soc/soc-dapm.c index
>>>>>>> c8a780d..4d2b35c 100644
>>>>>>> --- a/sound/soc/soc-dapm.c
>>>>>>> +++ b/sound/soc/soc-dapm.c
>>>>>>> @@ -514,9 +514,9 @@ static int dapm_connect_mux(struct
>>>>>> snd_soc_dapm_context *dapm,
>>>>>>>      	unsigned int val, item;
>>>>>>>      	int i;
>>>>>>>
>>>>>>> -	if (e->reg != SND_SOC_NOPM) {
>>>>>>> -		soc_widget_read(dest, e->reg, &val);
>>>>>>> -		val = (val >> e->shift_l) & e->mask;
>>>>>>> +	if (e->reg[0] != SND_SOC_NOPM) {
>>>>>>> +		soc_widget_read(dest, e->reg[0], &val);
>>>>>>> +		val = (val >> e->shift_l) & e->mask[0];
>>>>>>>      		item = snd_soc_enum_val_to_item(e, val);
>>>>>>
>>>>>> This probably should handle the new enum type as well. You'll
>>>>>> probably need some kind of flag in the struct to distinguish
>>>>>> between the two enum types.
>>>>>
>>>>> Any suggestion on the flag name ?
>>>>>
>>>>
>>>> How about 'onehot'?
>>>>
>>>> [...]
>>>>>>> +		reg_val = BIT(bit_pos);
>>>>>>> +	}
>>>>>>> +
>>>>>>> +	for (i = 0; i < e->num_regs; i++) {
>>>>>>> +		if (i == reg_idx) {
>>>>>>> +			change = snd_soc_test_bits(codec, e->reg[i],
>>>>>>> +							e->mask[i],
>>>>>> reg_val);
>>>>>>> +
>>>>>>> +		} else {
>>>>>>> +			/* accumulate the change to update the
>> DAPM
>>>>>> path
>>>>>>> +			    when none is selected */
>>>>>>> +			change += snd_soc_test_bits(codec, e-
>>> reg[i],
>>>>>>> +							e->mask[i], 0);
>>>>>>
>>>>>> change |=
>>>>>>
>>>>>>> +
>>>>>>> +			/* clear the register when not selected */
>>>>>>> +			snd_soc_write(codec, e->reg[i], 0);
>>>>>>
>>>>>> I think this should happen as part of the DAPM update sequence like
>>>>>> you had earlier. Some special care should probably be take to make
>>>>>> sure that you de-select the previous mux input before selecting the
>>>>>> new one if the new one is in a different register than the previous one.
>>>>>
>>>>> I am not sure I follow this part. We are clearing the 'not selected'
>>>>> registers before we set the one we want. Do you want us to loop the
>>>>> logic of soc_dapm_mux_update_power for each register ? or do you
>>>>> want to change the dapm_update structure so that it takes all the
>>>>> regs, masks, and values together ?
>>>>
>>>> The idea with the dapm_update struct is that the register updates are
>>>> done in the middle of the power-down and power-up sequence. So yes,
>>>> change the dapm_update struct to be able to hold all register updates
>>>> and do all register updates in dapm_widget_update. I think an earlier
>>>> version of your patch already had this.
>>>
>>> Is the change similar to as shown below?
>>>
>>> for (reg_idx = 0; reg_idx < e->num_regs; reg_idx++) {
>>> 	val = e->values[item * e->num_regs + reg_idx];
>>> 	ret = snd_soc_update_bits_locked(codec, e->reg[reg_idx],
>>> 				e->mask[reg_idx], val);
>>> 	if (ret)
>>> 	return ret;
>>> }
>>>
>>> During updating of the register's value, the above change can create
>>> non-zero value in two different registers (very short transition) as
>>> Mark mentioned for that change so we need to clear register first
>>> before writing the desired value in the register.
>>>
>>> Should we add the clearing all registers and write the mux value in
>>> desired register in the update function?
>>>
>>
>> In dapm_update_widget() you have this line:
>>
>>    ret = soc_widget_update_bits(w, update->reg, update->mask, update-
>>> val);
>>
>> That needs to be done for every register update. When you setup the
>> update struct you need to make sure that the register clears come before
>> the register set.
>>
>> E.g. if you have register 0x3, 0x4, 0x5 and you select a bit in register 0x4 it
>> should look like this.
>>
>> update->reg[0] = 0x3;
>> update->val[0] = 0x0;
>> update->reg[1] = 0x5;
>> update->val[1] = 0x0;
>> update->reg[2] = 0x4;
>> update->val[2] = 0x8;
>>
>> When you set a bit in register 0x3 it should look like this:
>>
>> update->reg[0] = 0x4;
>> update->val[0] = 0x0;
>> update->reg[1] = 0x5;
>> update->val[1] = 0x0;
>> update->reg[2] = 0x3;
>> update->val[2] = 0x1;
>>
>> So basically the write operation goes into update->reg[e->num_regs-1] the
>> clear operations go into the other slots before that.
>
> Does update reg/val array have the writing sequence, is it correct?
> And can I assume that update struct has reg/val/mask arrays not pointers?

Right now the update struct does not have support for multiple register 
writes. That's up to you to implement this. I guess making it an array for 
now should be fine. But you need to add some safety checks to make sure that 
num_regs is not larger or equal to the array size.