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

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Message-ID: <550FE05F.6070204@hmbedded.co.uk>
Date:	Mon, 23 Mar 2015 09:43:59 +0000
From:	Howard Mitchell <hm@...edded.co.uk>
To:	Mark Brown <broonie@...nel.org>
CC:	peda@...ntia.se, tiwai@...e.de, lgirdwood@...il.com,
	perex@...ex.cz, robh+dt@...nel.org, pawel.moll@....com,
	mark.rutland@....com, ijc+devicetree@...lion.org.uk,
	galak@...eaurora.org, devicetree@...r.kernel.org,
	alsa-devel@...a-project.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ASoC:pcm512x: Make PLL lock output selectable via device
 tree.

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)?
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