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

Stephen Boyd
2016-08-24T08:58:11Z

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?

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