Message-ID: <ZdbWRFyq42XFdp9E@surfacebook.localdomain>
Date: Thu, 22 Feb 2024 07:06:12 +0200
From: andy.shevchenko@...il.com
To: Théo Lebrun <theo.lebrun@...tlin.com>
Cc: 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>,
	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 v7 07/14] clk: eyeq5: add platform driver, and init
 routine at of_clk_init()

Wed, Feb 21, 2024 at 07:22:15PM +0100, Théo Lebrun kirjoitti:
> Add the Mobileye EyeQ5 clock controller driver. It might grow to add
> support for other platforms from Mobileye.
> 
> It handles 10 read-only PLLs derived from the main crystal on board. It
> exposes a table-based divider clock used for OSPI. Other platform
> clocks are not configurable and therefore kept as fixed-factor
> devicetree nodes.
> 
> Two PLLs are required early on and are therefore registered at
> of_clk_init(). Those are pll-cpu for the GIC timer and pll-per for the
> UARTs.

..

> +config COMMON_CLK_EYEQ5
> +	bool "Clock driver for the Mobileye EyeQ5 platform"

> +	depends on OF

Is this functional dependency? For compilation it seems you don't need it, also see below.

> +	depends on MACH_EYEQ5 || COMPILE_TEST
> +	default MACH_EYEQ5
> +	help
> +		This driver provides the clocks found on the Mobileye EyeQ5 SoC. Its
> +		registers live in a shared register region called OLB. It provides 10
> +		read-only PLLs derived from the main crystal clock which must be constant
> +		and one divider clock based on one PLL.

Wrong indentation, have you run checkpatch?

..

> +#include <linux/bitfield.h>
> +#include <linux/bits.h>
> +#include <linux/clk-provider.h>
> +#include <linux/mod_devicetable.h>

> +#include <linux/of_address.h>

Misused header. Also see below.

> +#include <linux/platform_device.h>

You have semi-random list of inclusions. Please, follow the IWUY principle.

Here I see _at least_ missing
array_size.h
err.h
io.h
slab.h
types.h

 
..

> +static int eq5c_pll_parse_registers(u32 r0, u32 r1, unsigned long *mult,
> +				    unsigned long *div, unsigned long *acc)
> +{
> +	if (r0 & PCSR0_BYPASS) {
> +		*mult = 1;
> +		*div = 1;
> +		*acc = 0;
> +		return 0;
> +	}
> +
> +	if (!(r0 & PCSR0_PLL_LOCKED))
> +		return -EINVAL;
> +
> +	*mult = FIELD_GET(PCSR0_INTIN, r0);
> +	*div = FIELD_GET(PCSR0_REF_DIV, r0);
> +	if (r0 & PCSR0_FOUTPOSTDIV_EN)

> +		*div *= FIELD_GET(PCSR0_POST_DIV1, r0) *
> +			FIELD_GET(PCSR0_POST_DIV2, r0);

One line?

> +	/* Fractional mode, in 2^20 (0x100000) parts. */
> +	if (r0 & PCSR0_DSM_EN) {
> +		*div *= 0x100000;
> +		*mult = *mult * 0x100000 + FIELD_GET(PCSR1_FRAC_IN, r1);
> +	}
> +
> +	if (!*mult || !*div)
> +		return -EINVAL;
> +
> +	/* Spread spectrum. */
> +	if (!(r1 & (PCSR1_RESET | PCSR1_DIS_SSCG))) {
> +		/*
> +		 * Spread is 1/1000 parts of frequency, accuracy is half of
> +		 * that. To get accuracy, convert to ppb (parts per billion).
> +		 */
> +		u32 spread = FIELD_GET(PCSR1_SPREAD, r1);

Missing blank line.

> +		*acc = spread * 500000;
> +		if (r1 & PCSR1_DOWN_SPREAD) {
> +			/*
> +			 * Downspreading: the central frequency is half a
> +			 * spread lower.
> +			 */
> +			*mult *= 2000 - spread;
> +			*div *= 2000;
> +		}
> +	} else {
> +		*acc = 0;
> +	}
> +
> +	return 0;
> +}

Looking at this function what I would do is to replace mul/div pair by
respective struct uXX_fract, add something like

#define mult_fract(fract, ...)		\
	...

and replace those

	*mult/*div *= ...

with

	mult_fract(fract, 2000);

etc.

..

> +static int eq5c_probe(struct platform_device *pdev)
> +{
> +	struct device *dev = &pdev->dev;
> +	struct device_node *np = dev->of_node;
> +	void __iomem *base_plls, *base_ospi;
> +	struct clk_hw *hw;
> +	int i;

> +	if (IS_ERR(eq5c_clk_data))
> +		return PTR_ERR(eq5c_clk_data);
> +	else if (!eq5c_clk_data)
> +		return -EINVAL;

Besides unneeded 'else', why so complicated? Can't you choose one: either NULL
or error pointer for the invalid state?

> +	base_plls = devm_platform_ioremap_resource_byname(pdev, "plls");
> +	base_ospi = devm_platform_ioremap_resource_byname(pdev, "ospi");

> +	if (!base_plls || !base_ospi)
> +		return -ENODEV;

Huh?! Are they not an error pointers and never be NULL?

> +	for (i = 0; i < ARRAY_SIZE(eq5c_plls); i++) {
> +		const struct eq5c_pll *pll = &eq5c_plls[i];
> +		unsigned long mult, div, acc;
> +		u32 r0, r1;
> +		int ret;
> +
> +		r0 = readl(base_plls + pll->reg);
> +		r1 = readl(base_plls + pll->reg + sizeof(r0));
> +
> +		ret = eq5c_pll_parse_registers(r0, r1, &mult, &div, &acc);
> +		if (ret) {
> +			dev_warn(dev, "failed parsing state of %s\n", pll->name);
> +			continue;
> +		}
> +
> +		hw = clk_hw_register_fixed_factor_with_accuracy_fwname(dev, np,
> +				pll->name, "ref", 0, mult, div, acc);
> +		eq5c_clk_data->hws[pll->index] = hw;

Why do you feel the data with errorneous one (in some cases)? It's quite
unusual pattern.

> +		if (IS_ERR(hw)) {
> +			dev_err(dev, "failed registering %s: %ld\n",
> +				pll->name, PTR_ERR(hw));
> +		}

Besides unnecessity of {} can't you unify the output format by using
dev_err_probe() in all error messages in ->probe()?

> +	}
> +
> +	hw = clk_hw_register_divider_table_parent_hw(dev, EQ5C_OSPI_DIV_CLK_NAME,
> +			eq5c_clk_data->hws[EQ5C_PLL_PER], 0,
> +			base_ospi, 0, EQ5C_OSPI_DIV_WIDTH, 0,
> +			eq5c_ospi_div_table, NULL);

> +	eq5c_clk_data->hws[EQ5C_DIV_OSPI] = hw;

Same as above.

> +	if (IS_ERR(hw)) {
> +		dev_err(dev, "failed registering %s: %ld\n",
> +			EQ5C_OSPI_DIV_CLK_NAME, PTR_ERR(hw));
> +	}

Same as above.

> +	return 0;
> +}

..

> +static struct platform_driver eq5c_driver = {
> +	.probe = eq5c_probe,
> +	.driver = {
> +		.name = "clk-eyeq5",
> +		.of_match_table = eq5c_match_table,
> +	},
> +};

> +

Redundant blank line.

> +builtin_platform_driver(eq5c_driver);

..

> +	index_plls = of_property_match_string(np, "reg-names", "plls");
> +	index_ospi = of_property_match_string(np, "reg-names", "ospi");
> +	if (index_plls < 0 || index_ospi < 0) {
> +		ret = -ENODEV;

Why error codes are shadowed?

> +		goto err;
> +	}

-- 
With Best Regards,
Andy Shevchenko

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