linux-kernel - Re: [PATCH v3 09/17] reset: eyeq5: add platform driver

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Date: Wed, 24 Jan 2024 17:52:13 +0100
From: Théo Lebrun <theo.lebrun@...tlin.com>
To: "Krzysztof Kozlowski" <krzysztof.kozlowski@...aro.org>, "Gregory
 CLEMENT" <gregory.clement@...tlin.com>, "Michael Turquette"
 <mturquette@...libre.com>, "Stephen Boyd" <sboyd@...nel.org>, "Rob Herring"
 <robh+dt@...nel.org>, "Krzysztof Kozlowski"
 <krzysztof.kozlowski+dt@...aro.org>, "Conor Dooley" <conor+dt@...nel.org>,
 "Thomas Bogendoerfer" <tsbogend@...ha.franken.de>, "Linus Walleij"
 <linus.walleij@...aro.org>, Rafał Miłecki
 <rafal@...ecki.pl>, "Philipp Zabel" <p.zabel@...gutronix.de>
Cc: "Vladimir Kondratiev" <vladimir.kondratiev@...ileye.com>,
 <linux-mips@...r.kernel.org>, <linux-clk@...r.kernel.org>,
 <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>, "Thomas
 Petazzoni" <thomas.petazzoni@...tlin.com>, "Tawfik Bayouk"
 <tawfik.bayouk@...ileye.com>, <linux-gpio@...r.kernel.org>
Subject: Re: [PATCH v3 09/17] reset: eyeq5: add platform driver

Hello,

On Wed Jan 24, 2024 at 8:00 AM CET, Krzysztof Kozlowski wrote:
> On 23/01/2024 19:46, Théo Lebrun wrote:
> > Add the Mobileye EyeQ5 reset controller driver. It belongs to a syscon
> > region called OLB. It might grow to add later support of other
> > platforms from Mobileye.

[...]

> > +static int _eq5r_busy_wait(struct eq5r_private *priv, struct device *dev,
> > +			   u32 domain, u32 offset, bool assert)
> > +{
> > +	unsigned int val, mask;
> > +	int i;
> > +
> > +	lockdep_assert_held(&priv->mutexes[domain]);
> > +
> > +	switch (domain) {
> > +	case 0:
> > +		for (i = 0; i < D0_TIMEOUT_POLL; i++) {
> > +			regmap_read(priv->olb, EQ5R_OLB_SARCR1, &val);
> > +			val = !(val & BIT(offset));
> > +			if (val == assert)
> > +				return 0;
> > +			__udelay(1);
>
> What is even "__udelay"? It is the first use in drivers. Please use
> common methods, like fsleep or udelay... but actually you should rather
> use regmap_read_poll_timeout() or some variants instead of open-coding it.

udelay is an alias to __udelay on MIPS, which is why this didn't look
odd to me. Fixed.

[...]

> > +static void _eq5r_assert(struct eq5r_private *priv, u32 domain, u32 offset)
>
> Drop leading _ and name the function in some informative way.

Fixed by turning `_eq5r_assert` into `eq5r_assert_withlock`, and co.

[...]

> > +
> > +static int eq5r_probe(struct platform_device *pdev)
> > +{
> > +	struct device *dev = &pdev->dev;
> > +	struct device_node *np = dev->of_node;
> > +	struct device_node *parent_np = of_get_parent(np);
> > +	struct eq5r_private *priv;
> > +	int ret, i;
> > +
> > +	priv = kzalloc(sizeof(*priv), GFP_KERNEL);
> > +	if (!priv)
> > +		return -ENOMEM;
>
> You leak parent.

Fixed in all three clk+reset+pinctrl drivers. They all had this issue.

>
> > +
> > +	dev_set_drvdata(dev, priv);
> > +
> > +	priv->olb = ERR_PTR(-ENODEV);
> > +	if (parent_np) {
> > +		priv->olb = syscon_node_to_regmap(parent_np);
> > +		of_node_put(parent_np);
> > +	}
> > +	if (IS_ERR(priv->olb))
>
> Also here
>
> > +		return PTR_ERR(priv->olb);
>
> This looks over-complicated. First, you cannot just
> dev_get_regmap(pdev->dev.parent)?

No dev_get_regmap() cannot be used as it doesn't pick up syscon regmaps.
I've just tried it.

However I've simplified the logic, it looks better now.

	static int eq5r_probe(struct platform_device *pdev)
	{
		struct device_node *parent_np;

		/* ... */

		parent_np = of_get_parent(np);
		if (!parent_np)
			return -ENODEV;

		priv->olb = syscon_node_to_regmap(parent_np);
		of_node_put(parent_np);
		if (IS_ERR(priv->olb))
			return PTR_ERR(priv->olb);

		/* ... */
	}

[...]

> > +static struct platform_driver eq5r_driver = {
> > +	.probe = eq5r_probe,
> > +	.driver = {
> > +		.name = "eyeq5-reset",
> > +		.of_match_table = eq5r_match_table,
> > +	},
> > +};
> > +
> > +static int __init eq5r_init(void)
> > +{
> > +	return platform_driver_register(&eq5r_driver);
> > +}
> > +
> > +arch_initcall(eq5r_init);
>
> This is does not look like arch code, but driver or subsys. Use regular
> module_driver. I see there is such pattern in reset but I doubt this is
> something good.

Indeed I've moved things to using the builtin_platform_driver() macro.

Thanks,

--
Théo Lebrun, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com