linux-kernel - Re: [PATCH] ASoC:pcm512x: Make PLL lock output selectable via device tree.

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Date:	Mon, 23 Mar 2015 11:14:09 +0000
From:	Howard Mitchell <hm@...edded.co.uk>
To:	Peter Rosin <peda@...ntia.se>, Mark Brown <broonie@...nel.org>
CC:	"tiwai@...e.de" <tiwai@...e.de>,
	"lgirdwood@...il.com" <lgirdwood@...il.com>,
	"perex@...ex.cz" <perex@...ex.cz>,
	"robh+dt@...nel.org" <robh+dt@...nel.org>,
	"pawel.moll@....com" <pawel.moll@....com>,
	"mark.rutland@....com" <mark.rutland@....com>,
	"ijc+devicetree@...lion.org.uk" <ijc+devicetree@...lion.org.uk>,
	"galak@...eaurora.org" <galak@...eaurora.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"alsa-devel@...a-project.org" <alsa-devel@...a-project.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ASoC:pcm512x: Make PLL lock output selectable via device
 tree.



On 23/03/15 11:00, Peter Rosin wrote:
> Howard Mitchell wrote:
>> On 22/03/15 16:24, Mark Brown wrote:
>>> On Fri, Mar 20, 2015 at 09:22:43PM +0000, Howard Mitchell wrote:
>>>
>>>> +	if (pcm512x->pll_lock) {
>>>> +                if (of_property_read_u32(np, "pll-lock", &val) >= 0) {
>>>> +                        if (val > 6) {
>>>> +                                dev_err(dev, "Invalid pll-lock\n");
>>>> +                                ret = -EINVAL;
>>>> +                                goto err_clk;
>>>> +                        }
>>>> +                        pcm512x->pll_lock = val;
>>>> +                }
>>> This breaks existing boards which rely on GPIO 4 being set as the lock
>>> output.  This is very unfortunate since it's a silly thing for the
>>> driver to default to but nontheless we should really continue to support
>>> them - at a guess Peter's board is relying on this, and even if it isn't
>>> someone else's might.
>> I take your point, but the reason I pushed this patch was that I wanted
>> to use GPIO4 for pll-out and unfortunately because the pll-lock
>> configuration is after the pll-out configuration it stomps on it. If I
>> modify the patch to provide a default for pll-lock I will then be
>> obliged to specify pll-lock on another GPIO. The pcm5122 has limited IO
>> so being forced to have a GPIO for pll-lock seems wrong to me. A future
>> user of the device may well decide to use the GPIOs for other purposes
>> and therefore not want a pll-lock signal at all. Surely we should allow
>> for that possibility?
>>
>> Given that Peter has indicated that he'd be happy with this solution and
>> that this code hasn't reached a published kernel would it be reasonable
>> to go ahead with my current patch (happy to clean up the indent issues
>> that Peter pointed out of course)?
> Strongly agreed that we should fix this before it is published (I assumed
> that is was included in 3.19, it felt so long ago that Mark merged it...). My
> preference would be to remove the pll-lock things entirely though. Assuming
> you don't need it for your board of course, but I doubt it from your description.
> I used it to make sure I had understood the chip correctly, that's all.
>
> Cheers,
> Peter
>
I'd be happy to remove it entirely. I only used it as you did as a debug 
tool. Let's see what Mark thinks.....

- Howard
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