Re: [PATCH v7 07/14] clk: eyeq5: add platform driver, and init routine at of_clk_init()

andy.shevchenko
2024-02-22T05:06:16Z

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