Re: [PATCH 8/9] mfd: wm97xx-core: core support for wm97xx Codec

Lee Jones
2016-11-21T10:09:22Z

Mark, please see below:

On Sat, 19 Nov 2016, Robert Jarzmik wrote:
> Lee Jones <lee.jones@linaro.org> writes:
>
> >> +#define WM9705_VENDOR_ID 0x574d4c05
> >> +#define WM9712_VENDOR_ID 0x574d4c12
> >> +#define WM9713_VENDOR_ID 0x574d4c13
> >> +#define WM97xx_VENDOR_ID_MASK 0xffffffff
> >
> > These are probably better represented as enums.
> These are ids, just as devicetree ids, or PCI ids, I don't think an enum will
> fit.

That's fine. We can use enums to simply group items of a similar
type. Representing these as enums would only serve to benefit code
cleanliness. What makes you think they won't fit?

> >> +struct wm97xx_priv {
> >> + struct regmap *regmap;
> >> + struct snd_ac97 *ac97;
> >> + struct device *dev;
> >> +};
> >
> > Replace _priv with _ddata.
> Ok, will do, would you care to explain if this is something specific to your mfd
> tree, or is it a kernel overall recommendation ?

It's personal preference. But these aren't necessarily private, so
priv doesn't really make a great deal of sense. These types of saved
pointers are better described as device data (ddata).

[...]

> >> +static const struct reg_default wm97xx_reg_defaults[] = {
> >> +};
> >
> > What's the point in this?
> Ah, that's a reminder I have still more work on this patch ... Either I remove
> support for wm9705 and wm9712 in the first version, or I complete it and add the
> tables :
> - wm9705_reg_defaults
> - wm9712_reg_defaults

Please don't add redundant code. I suggest you remove it for this
submission.

> >> +static int wm9705_register(struct wm97xx_priv *wm97xx)
> >> +{
> >> + return 0;
> >> +}
> >> +
> >> +static int wm9712_register(struct wm97xx_priv *wm97xx)
> >> +{
> >> + return 0;
> >> +}
> >
> > I don't get it?
> >
> > Either populate or don't provide.
> Same story as above, either I complete wm9705 and wm9712 support or I remove it.

Remove it please.

> >> +static int wm9713_register(struct wm97xx_priv *wm97xx,
> >> + struct wm97xx_pdata *pdata)
> >> +{
> >
> > What are you lining this up with?
> Emacs ... I don't see your point though, seeing it not aligned in the diff chunk
> doesn't mean it's not properly aligned.

That is true. So the two "scruct"s are line up in the source file,
right?

[...]

> >> + codec_pdata.ac97 = wm97xx->ac97;
> >> + codec_pdata.regmap = devm_regmap_init_ac97(wm97xx->ac97,
> >> + &wm9713_regmap_config);
> >> + codec_pdata.batt_pdata = pdata->batt_pdata;
> >> + if (IS_ERR(codec_pdata.regmap))
> >> + return PTR_ERR(codec_pdata.regmap);
> >
> > This doesn't look like pdata. You can get rid of all of this hoop
> > jumping if you add it to ddata and set it as such.
> You mean I should pass ddata to mfd sub-cells, right ?

Correct.

[...]

> >> +static int wm97xx_ac97_probe(struct ac97_codec_device *adev)
> >
> > This looks sound specific.
> >
> > Why isn't this a plane platform driver?
> That's the whole purpose of the patch serie.
>
> This serie transforms the wm97xx drivers from a platform driver model to an ac97
> model, where the ac97 devices are automatically discovered. The long explanation
> is in patch 0/9, on how it started and what is the global purpose.
>
> The short story is : switch to the new AC97 bus driver model.
>
> As for the "sound specific part", it's because AC97 bus is mainly used in sound
> oriented drivers, but still the codec IPs provide more than just sound, as the
> Wolfson codecs for instance.

I'd like to get Mark Brown's opinion on this.

> >> +{
> >> + struct wm97xx_priv *wm97xx;
> >> + int ret;
> >> + void *pdata = snd_ac97_codec_get_platdata(adev);
> >> +
> >> + wm97xx = devm_kzalloc(ac97_codec_dev2dev(adev),
> >> + sizeof(*wm97xx), GFP_KERNEL);
> >> + if (!wm97xx)
> >> + return -ENOMEM;
> >> +
> >> + wm97xx->dev = ac97_codec_dev2dev(adev);
> >> + wm97xx->ac97 = snd_ac97_compat_alloc(adev);
> >> + if (IS_ERR(wm97xx->ac97))
> >> + return PTR_ERR(wm97xx->ac97);
> >> +
> >> +
> >> + ac97_set_drvdata(adev, wm97xx);
> >> + dev_info(wm97xx->dev, "wm97xx core found, id=0x%x\n",
> >> + adev->vendor_id);
> >
> > All of this ac97/sound stuff should be done in the ac97/sound driver.
>
> Nope, it's not sound adherence you're seeing here, it's ac97 bus and driver
> model adherence you're seeing. Would the bus be in drivers/ac97 instead of
> sound/ac97, the code would remain the same, would be bus be i2c you would see
> the same kind of calls but with i2c_xxx and not ac97_xxx.
>
> The wm97xx needs an ac97 bus to interact with the hardware, to provide sound,
> gpio, adc, etc ... functions. That's what is expressed here, and the fact that
> this ac97 access has to shared amongst the mfd sub-cells, and that these cells
> require :
> - wm97xx->ac97 : this one is for drivers/input/touchscreen/wm97xx-core.c
>
> So the requirement in this case is not for ac97/sound but input/touchscreen.
>
> >> diff --git a/include/linux/mfd/wm97xx.h b/include/linux/mfd/wm97xx.h
> >> new file mode 100644
> >> index 000000000000..627322f14d48
> >> --- /dev/null
> >> +++ b/include/linux/mfd/wm97xx.h
> >> @@ -0,0 +1,31 @@
> >> +/*
> >> + * wm97xx client interface
> >> + *
> >> + * Copyright (C) 2016 Robert Jarzmik
> >> + *
> >> + * This program is free software; you can redistribute it and/or modify
> >> + * it under the terms of the GNU General Public License as published by
> >> + * the Free Software Foundation; either version 2 of the License, or
> >> + * (at your option) any later version.
> >> + *
> >> + * This program is distributed in the hope that it will be useful,
> >> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> >> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
> >> + * GNU General Public License for more details.
> >> + */
> >> +
> >> +#ifndef __LINUX_MFD_WM97XX_H
> >> +#define __LINUX_MFD_WM97XX_H
> >> +
> >> +struct regmap;
> >> +struct wm97xx_batt_pdata;
> >> +struct snd_ac97;
> >
> > Why can't you just add the include files?
> I could, but I don't need to, do I ?
> Moreover, if a mfd sub-cell doesn't use regmap for example, I won't include a
> useless define.
>
> Thanks for the review, Lee. This will iterate, I'll split out mfd patch(es) to
> follow up the review with you and Mark to lessen the burden on your mailbox.
>
> Cheers.
>

--
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
Follow Linaro: Facebook | Twitter | Blog