Re: [PATCH v3 02/13] mfd: wcd9335: add support to wcd9335 core

[Lee Jones <lee.jones@linaro.org>]

On Wed, 12 Sep 2018, Srinivas Kandagatla wrote:

> 
> 
> On 12/09/18 09:58, Lee Jones wrote:
> > > > > +static const struct mfd_cell wcd9335_devices[] = {
> > > > > +	{ .name = "wcd9335-codec", },
> > > > > +};
> > > > Are there more devices to come?
> > > > 
> > > Yes, that is the plan, we are kind of limited in hardware setup to test few
> > > things like soundwire controller. We are exploring other ways to test these.
> > I normally don't accept MFDs with just one device enabled.  Since it's
> > not really an MFD (M == Multi) until it has more than one function.
> > 
> 
> WCD9335 Codec hw itself has multiple hw blocks.
> 
> If the issue is about adding more entries to mfd cells then we should be
> able to add below entry:
> 
> 	{ .name = "wcd9335-soundwire-controller", },
> 
> Actual driver for soundwire controller is not something We can test with
> regular dragon boards, it needs special hw for smart speakers. Once we have
> that we can test and post the drivers for that.
> 
> Otherwise
> 
> Are you suggesting that I move everything to  sound/soc/codecs and then back
> to mfd once soundwire controller driver is added?

My preference would be for you to add at least one other (tested)
device.  However, in your case I know where you live, so I can throw
tomatoes at your house if you don't upstream more device support
promptly! ;)

When will you be enabling more devices?  If the answer is 'never',
then creating an MFD is a waste of time.

> > [...]
> > 
> > > > > +	struct device_node *ifc_dev_np;
> > > > ifc isn't very forthcoming.  Any way you can improve the name?
> > > ifc was suggested in dt bindings by Rob,  I can proably rename to
> > > interface_node.
> > ifc is a horrible variable name - just sayin'.
> > 
> > [...]
> > 
> > > > > +	ret = wcd9335_bring_up(wcd);
> > > > So the device_status call-back brings up the hardware?
> > > > 
> > > device status reports the device status at runtime. We can not communicate
> > > with the device until it is up, enumerated by slimbus and a logical address
> > > is assigned to it. So the best place to initialize it is in status callback
> > > where all the above are expected to be done.
> > Right, I understand what's happening.  I just think the semantics are
> > wrong.  The Subsystem (I'm assuming it's a Subsystem) requests for
> > status and it ends up initiating a start-up sequence.  Just from a
> > purist's point of view (I understand that it "works"), it's not good
> > practice.
> > 
> > > Probe is expected to setup the external configurations like regulators/pins
> > > and so on which gets the device out of reset and ready to be enumerated by
> > > the slimbus controller.
> > I suggest fully starting the device in probe() is a better approach.
> > 
> Its catch-22 situation, without device being powered up and reset correctly
> there is no way to enumerate it.

Isn't power-up and reset also done in probe()?

What am I missing?

> > [...]
> > 
> > > > > +struct wcd9335 {
> > > > > +	int version;
> > > > > +	int intr1;
> > > > What's this?  If I have to ask, it's probably not a good name.
> > > > 
> > > This is a hardware pin name for interrupt line 1.
> > I don't see how this is used, so it's difficult for me to advise
> > fully, but I find this confusing.  Pin name/number?  Shouldn't this be
> > handed by Pinctrl?
> > 
> This is represented as proper irq line in dt via  pintrl irq controller.

So why can't it just be 'irq' like most of the time?

What is the 1 in reference to?  Will there be a 2?

> > intr1 could be quite ambiguous.  Especually as the '1' could easily be
> > read as an 'l'.  Suggest that 'irq1' or 'irq_1' or 'irq_one'.
> 
> I can change this to something more readable in next version or may be I can
> even remove it may be just use a local variable.

If it's possible for it to be a local variable, then it should not be
placed in device data.

-- 
Lee Jones [李琼斯]
Linaro Services Technical Lead
Linaro.org │ Open source software for ARM SoCs
Follow Linaro: Facebook | Twitter | Blog