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

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Date:	Mon, 23 Mar 2015 11:00:53 +0000
From:	Peter Rosin <peda@...ntia.se>
To:	Howard Mitchell <hm@...edded.co.uk>,
	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.

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

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