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Date:   Tue, 4 Apr 2023 10:07:59 +0200
From:   Herve Codina <herve.codina@bootlin.com>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Cc:     Lee Jones <lee@kernel.org>, Rob Herring <robh+dt@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        Liam Girdwood <lgirdwood@gmail.com>,
        Mark Brown <broonie@kernel.org>,
        Jaroslav Kysela <perex@perex.cz>,
        Takashi Iwai <tiwai@suse.com>, linux-kernel@vger.kernel.org,
        devicetree@vger.kernel.org, alsa-devel@alsa-project.org,
        Christophe Leroy <christophe.leroy@csgroup.eu>,
        Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Subject: Re: [PATCH v5 2/5] mfd: Add support for the Lantiq PEF2256 framer
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On Tue, 4 Apr 2023 09:23:36 +0200
Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org> wrote:

> On 04/04/2023 09:20, Herve Codina wrote:
> >> I suggest that none of this (besides the child registration, which is
> >> achieved by a simple OF API call in this case) has anything to do with
> >> MFD.  We are not requesting and initialising shared resources and we are
> >> not using the MFD API to register children.  The pin control
> >> functionality clearly needs moving to Pinctrl and the rest, if you
> >> cannot find a suitable home for it *may be* suitable for Misc.
> >>  
> > 
> > I am confused and I am not really sure to understand where to put my driver.
> > 
> > The core pef2256.c needs to:
> > 1) setup the pef2256
> > 2) add the children
> > 
> > To add the children it calls  devm_of_platform_populate() to add the audio
> > parts as several audio children can be available with the same compatible
> > string.
> > 
> > I plan to move the pinctrl part to the pinctrl subsystem. With this done,
> > the core pef2256.c will probably add the children using:
> > - a mfd_cell for the pinctrl part
> > - devm_of_platform_populate() for the audio children
> > 
> > The setup (E1 lines and TDM configuration) still needs to be done by the
> > core pef2256.c. Moving this part only to Misc will break the hierarchy.
> > The audio children depends on the core pef2256.c as this one do the setup.
> > Having in the audio children and the part that do the setup in same hierarchy
> > level is not correct. Audio children should be children of the part that do
> > the setup.
> > 
> > So, the structure I have in mind:
> > - pef2256.c (MFD)
> >   implement and do the setup at probe()
> >   Add the children at probe():
> >     - pef2256-pinctrl (pinctrl) added using mfd_add_devices()
> >     - pef2256-codec (ASoC codec) added using devm_of_platform_populate()
> > 
> > Lee, with this in mind, can the core pef2256.c be a MFD driver ?  
> 
> You do not use MFD here, so why do you want to keep it in MFD? If you
> disagree, please tell me where is the MFD code in your patch?

I don't want to absolutely use MFD.
I just want to put my driver somewhere and I don't know the right location
between MFD and Misc.

Basically, the driver needs to do (little simplified and error path removed):

  static const struct mfd_cell pef2256_devs[] = {
  	{ .name = "lantiq-pef2256-pinctrl", },
  };

  static int pef2256_probe(struct platform_device *pdev)
  {
	struct pef2256 *pef2256;
	void __iomem *iomem;
	int ret;
	int irq;

	pef2256 = devm_kzalloc(&pdev->dev, sizeof(*pef2256), GFP_KERNEL);
	if (!pef2256)
		return -ENOMEM;

	pef2256->dev = &pdev->dev;

	iomem = devm_platform_ioremap_resource(pdev, 0);

	pef2256->regmap = devm_regmap_init_mmio(&pdev->dev, iomem,
						&pef2256_regmap_config);

	pef2256->mclk = devm_clk_get_enabled(&pdev->dev, "mclk");
	pef2256->sclkr = devm_clk_get_enabled(&pdev->dev, "sclkr");
	pef2256->sclkx = devm_clk_get_enabled(&pdev->dev, "sclkx");

	pef2256->reset_gpio = devm_gpiod_get_optional(&pdev->dev, "reset", GPIOD_OUT_LOW);
	if (pef2256->reset_gpio) {
		gpiod_set_value_cansleep(pef2256->reset_gpio, 1);
		udelay(10);
		gpiod_set_value_cansleep(pef2256->reset_gpio, 0);
		udelay(10);
	}

	pef2556_of_parse(pef2256, np);

	irq = platform_get_irq(pdev, 0);
	ret = devm_request_irq(pef2256->dev, irq, pef2256_irq_handler, 0, "pef2256", pef2256);

	platform_set_drvdata(pdev, pef2256);

	mfd_add_devices(pef2256->dev, PLATFORM_DEVID_NONE, pef2256_devs,
	      		ARRAY_SIZE(pef2256_devs), NULL, 0, NULL);

	pef2256_setup(pef2256);

	devm_of_platform_populate(pef2256->dev);
	
	return 0;
  }

> 
> Best regards,
> Krzysztof
> 


-- 
Hervé Codina, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com