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

[Songhee Baek]

> -----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?

> 
> - Lars