linux-kernel - Re: [PATCH v3 2/2] ASoC: msm8916: Add msm8916-wcd codec driver

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Message-ID: <20160615093136.GW2282@sirena.org.uk>
Date:	Wed, 15 Jun 2016 10:31:36 +0100
From:	Mark Brown <broonie@...nel.org>
To:	Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
Cc:	alsa-devel@...a-project.org, Rob Herring <robh+dt@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	Liam Girdwood <lgirdwood@...il.com>,
	Jaroslav Kysela <perex@...ex.cz>,
	Takashi Iwai <tiwai@...e.com>, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, kwestfie@...eaurora.org,
	plai@...eaurora.org, linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH v3 2/2] ASoC: msm8916: Add msm8916-wcd codec driver

On Wed, Jun 15, 2016 at 10:16:27AM +0100, Srinivas Kandagatla wrote:
> On 14/06/16 16:59, Mark Brown wrote:
> > On Fri, Jun 10, 2016 at 07:18:45PM +0100, Srinivas Kandagatla wrote:

> > > +config SND_SOC_MSM8916_WCD
> > > +	tristate "Qualcomm MSM8916 WCD"
> > > +	depends on SPMI && MFD_SYSCON

> > Normally users select MFD_SYSCON.

> This driver is child of spmi bus so, we need SPMI dependency here along with
> SYSCON.

That does not seem relevant to the problem with depending on MFD_SYSCON.

> > > +#include "msm8916-wcd-registers.h"
> > > +#include "msm8916-wcd.h"
> > > +#include "dt-bindings/sound/msm8916-wcd.h"

> > What's in here?  There weren't any constants in the bindings.

> Yes, there are DAI id's which are used in device trees.

That doesn't make them present in the binding document...

> > Why is this one device and not two devices?  The description indicated
> > that this was two separate bits of silicon.

> In theory there are 3 devices,
> one is the pmic-spmi driver, which provides regmap access to analog part of
> codec registers.
> second is syscon driver which provides regmap access to digital parts of
> codec to codec driver.
> third is the codec driver which uses both the above.

> Codec registers range is just split into two, range 0x0- 0x200 sits in pmic
> address space and range 0x201 - 0x4ff in the SOC address space,

> Are there any other better ways to model this kinda driver?

Why not just have separate devices for each of the register maps?

> > > +static const struct of_device_id msm8916_wcd_match_table[] = {
> > > +	{.compatible = "qcom,msm8916-pmic-wcd-codec"},
> > > +	{}
> > > +};

> > We were peering inside the parent for the register map, why does this

> I think that's the only way/interface to access PMIC spmi registers I guess.

Don't guess, understand what the code is doing.

> > appear in the device tree as a separate device?  Both the patch

> This node is child of spmi bus, like the other spmi devices.

If this is a SPMI device it needs to register a SPMI device not a
platform device.

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