Re: [PATCH V5] clk: bcm: Add driver for BCM53573 ILP clock

[Stephen Boyd <sboyd@codeaurora.org>]

On 08/23, Rafał Miłecki wrote:
> diff --git a/drivers/clk/bcm/clk-bcm53573-ilp.c b/drivers/clk/bcm/clk-bcm53573-ilp.c
> new file mode 100644
> index 0000000..b7ac0eb
> --- /dev/null
> +++ b/drivers/clk/bcm/clk-bcm53573-ilp.c
> @@ -0,0 +1,146 @@
> +/*
> + * Copyright (C) 2016 Rafał Miłecki <rafal@milecki.pl>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + */
> +
> +#include <linux/clk.h>

Is this include used?

> +#include <linux/clk-provider.h>
> +#include <linux/err.h>
> +#include <linux/io.h>
> +#include <linux/of.h>
> +#include <linux/of_address.h>
> +#include <linux/slab.h>
> +
> +#define PMU_XTAL_FREQ_RATIO			0x66c
> +#define  XTAL_ALP_PER_4ILP			0x00001fff
> +#define  XTAL_CTL_EN				0x80000000
> +#define PMU_SLOW_CLK_PERIOD			0x6dc
> +
> +struct bcm53573_ilp {
> +	struct clk *clk;
> +	struct clk_hw hw;
> +	void __iomem *pmu;
> +};
> +
> +static int bcm53573_ilp_enable(struct clk_hw *hw)
> +{
> +	struct bcm53573_ilp *ilp = container_of(hw, struct bcm53573_ilp, hw);
> +
> +	writel(0x10199, ilp->pmu + PMU_SLOW_CLK_PERIOD);
> +	writel(0x10000, ilp->pmu + 0x674);

Is there a name for 0x674?
> +
> +	return 0;
> +}
> +
> +static unsigned long bcm53573_ilp_recalc_rate(struct clk_hw *hw,
> +					      unsigned long parent_rate)
> +{
> +	struct bcm53573_ilp *ilp = container_of(hw, struct bcm53573_ilp, hw);
> +	void __iomem *pmu = ilp->pmu;
> +	u32 last_val, cur_val;
> +	u32 sum = 0, num = 0, loop_num = 0;

Should these just be plain ints? Do we care about sizes for these
variables?

> +	u32 avg;

This one too.

> +
> +	/* Enable measurement */
> +	writel(XTAL_CTL_EN, pmu + PMU_XTAL_FREQ_RATIO);
> +
> +	/* Read initial value */
> +	last_val = readl(pmu + PMU_XTAL_FREQ_RATIO) & XTAL_ALP_PER_4ILP;
> +
> +	/*
> +	 * At minimum we should loop for a bit to let hardware do the
> +	 * measurement. This isn't very accurate however, so for a better
> +	 * precision lets try getting 20 different values for and use average.
> +	 */
> +	while (num < 20) {
> +		cur_val = readl(pmu + PMU_XTAL_FREQ_RATIO) & XTAL_ALP_PER_4ILP;
> +
> +		if (cur_val != last_val) {
> +			/* Got different value, use it */
> +			sum += cur_val;
> +			num++;
> +			loop_num = 0;
> +			last_val = cur_val;
> +		} else if (++loop_num > 5000) {
> +			/* Same value over and over, give up */
> +			sum += cur_val;
> +			num++;
> +			break;
> +		}

Should there be a udelay() here? Or we're expected to tight loop
read the hardware? If so we should throw in a cpu_relax() here to
indicate tight loop.

> +	}
> +
> +	/* Disable measurement to save power */
> +	writel(0x0, pmu + PMU_XTAL_FREQ_RATIO);
> +
> +	avg = sum / num;
> +
> +	return parent_rate * 4 / avg;
> +}
> +
> +static const struct clk_ops bcm53573_ilp_clk_ops = {
> +	.enable = bcm53573_ilp_enable,

No disable? Or .is_enabled?

> +	.recalc_rate = bcm53573_ilp_recalc_rate,
> +};
> +
> +static void bcm53573_ilp_init(struct device_node *np)
> +{
> +	struct bcm53573_ilp *ilp;
> +	struct resource res;
> +	struct clk_init_data init = { 0 };
> +	const char *parent_name;
> +	int index;
> +	int err;
> +
> +	ilp = kzalloc(sizeof(*ilp), GFP_KERNEL);
> +	if (!ilp)
> +		return;
> +
> +	parent_name = of_clk_get_parent_name(np, 0);
> +	if (!parent_name) {
> +		err = -ENOENT;
> +		goto err_free_ilp;
> +	}
> +
> +	/* TODO: This looks generic, try making it OF helper. */
> +	index = of_property_match_string(np, "reg-names", "pmu");
> +	if (index < 0) {
> +		err = index;
> +		goto err_free_ilp;
> +	}
> +	err = of_address_to_resource(np, index, &res);
> +	if (err)
> +		goto err_free_ilp;
> +	ilp->pmu = ioremap(res.start, resource_size(&res));
> +	if (IS_ERR(ilp->pmu)) {
> +		err = PTR_ERR(ilp->pmu);
> +		goto err_free_ilp;
> +	}
> +
> +	init.name = np->name;
> +	init.ops = &bcm53573_ilp_clk_ops;
> +	init.parent_names = &parent_name;
> +	init.num_parents = 1;
> +
> +	ilp->hw.init = &init;
> +	ilp->clk = clk_register(NULL, &ilp->hw);

please use clk_hw_register() and of_clk_add_hw_provider().

> +	if (WARN_ON(IS_ERR(ilp->clk)))
> +		goto err_unmap_pmu;
> +
> +	err = of_clk_add_provider(np, of_clk_src_simple_get, ilp->clk);
> +	if (err)
> +		goto err_clk_unregister;
> +
> +	return;
> +
> +err_clk_unregister:
> +	clk_unregister(ilp->clk);
> +err_unmap_pmu:
> +	iounmap(ilp->pmu);
> +err_free_ilp:
> +	kfree(ilp);
> +	pr_err("Failed to init ILP clock: %d\n", err);
> +}
> +CLK_OF_DECLARE(bcm53573_ilp_clk, "brcm,bcm53573-ilp", bcm53573_ilp_init);

Can this be a platform driver instead?

-- 
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
a Linux Foundation Collaborative Project