Re: [PATCH 3/6] clk: mvebu: add CPU clock driver for Armada 7K/8K

From: Stephen Boyd
Date: Wed Oct 17 2018 - 14:28:17 EST

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Quoting Gregory CLEMENT (2018-09-22 11:17:06)
> diff --git a/drivers/clk/mvebu/ap-cpu-clk.c b/drivers/clk/mvebu/ap-cpu-clk.c
> new file mode 100644
> index 000000000000..1b498cfe9191
> --- /dev/null
> +++ b/drivers/clk/mvebu/ap-cpu-clk.c
> @@ -0,0 +1,265 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +/*
> + * Marvell Armada AP CPU Clock Controller
> + *
> + * Copyright (C) 2018 Marvell
> + *
> + * Omri Itach <omrii@xxxxxxxxxxx>
> + * Gregory Clement <gregory.clement@xxxxxxxxxxx>
> + */
> +
> +#define pr_fmt(fmt) "ap-cpu-clk: " fmt
> +
> +#include "armada_ap_cp_helper.h"

Does this include need to come first? Preferably local includes come
after any <linux> ones.

> +#include <linux/clk-provider.h>
> +#include <linux/clk.h>
> +#include <linux/init.h>

Is this used?

> +#include <linux/mfd/syscon.h>
> +#include <linux/of.h>
> +#include <linux/of_address.h>
> +#include <linux/platform_device.h>
> +#include <linux/regmap.h>
> +
> +#define AP806_CPU_CLUSTER0 0
> +#define AP806_CPU_CLUSTER1 1
> +#define AP806_CPUS_PER_CLUSTER 2
> +#define APN806_CPU1_MASK 0x1
> +
> +#define APN806_CLUSTER_NUM_OFFSET 8
> +#define APN806_CLUSTER_NUM_MASK (1 << APN806_CLUSTER_NUM_OFFSET)
> +
> +#define APN806_MAX_DIVIDER 32
> +
> +/* AP806 CPU DFS register mapping*/
> +#define AP806_CA72MP2_0_PLL_CR_0_REG_OFFSET 0x278
> +#define AP806_CA72MP2_0_PLL_CR_1_REG_OFFSET 0x280
> +#define AP806_CA72MP2_0_PLL_CR_2_REG_OFFSET 0x284
> +#define AP806_CA72MP2_0_PLL_SR_REG_OFFSET 0xC94
> +
> +#define AP806_CA72MP2_0_PLL_CR_CLUSTER_OFFSET 0x14
> +#define AP806_PLL_CR_0_CPU_CLK_DIV_RATIO_OFFSET 0
> +#define AP806_PLL_CR_0_CPU_CLK_DIV_RATIO_MASK \
> + (0x3f << AP806_PLL_CR_0_CPU_CLK_DIV_RATIO_OFFSET)
> +#define AP806_PLL_CR_0_CPU_CLK_RELOAD_FORCE_OFFSET 24
> +#define AP806_PLL_CR_0_CPU_CLK_RELOAD_FORCE_MASK \
> + (0x1 << AP806_PLL_CR_0_CPU_CLK_RELOAD_FORCE_OFFSET)
> +#define AP806_PLL_CR_0_CPU_CLK_RELOAD_RATIO_OFFSET 16
> +#define AP806_CA72MP2_0_PLL_RATIO_STATE 11
> +
> +#define to_clk(hw) container_of(hw, struct ap_cpu_clk, hw)
> +
> +/*
> + * struct ap806_clk: CPU cluster clock controller instance
> + * @cluster: Cluster clock controller index
> + * @clk_name: Cluster clock controller name
> + * @dev : Cluster clock device
> + * @hw: HW specific structure of Cluster clock controller
> + * @pll_cr_base: CA72MP2 Register base (Device Sample at Reset register)
> + */
> +struct ap_cpu_clk {
> + int cluster;

unsigned?

> + const char *clk_name;
> + struct device *dev;
> + struct clk_hw hw;
> + struct regmap *pll_cr_base;
> +};
> +
> +static struct clk **cluster_clks;
> +static struct clk_onecell_data clk_data;

Can you give these some better names that are ap_cpu specific? Grepping
for clk_data will make lots of hits otherwise because they're so
generic.

> +
> +static unsigned long ap_cpu_clk_recalc_rate(struct clk_hw *hw,
> + unsigned long parent_rate)
> +{
> + struct ap_cpu_clk *clk = to_clk(hw);
> + unsigned int cpu_clkdiv_reg = AP806_CA72MP2_0_PLL_CR_0_REG_OFFSET +
> + (clk->cluster * AP806_CA72MP2_0_PLL_CR_CLUSTER_OFFSET);

Nitpick: This is pretty unreadable. Can you just declare the variables
up here and then do the assignment later on in the function and avoid
splitting across many lines?

> + int cpu_clkdiv_ratio;
> +
> + regmap_read(clk->pll_cr_base, cpu_clkdiv_reg, &cpu_clkdiv_ratio);
> + cpu_clkdiv_ratio &= AP806_PLL_CR_0_CPU_CLK_DIV_RATIO_MASK;
> + cpu_clkdiv_ratio >>= AP806_PLL_CR_0_CPU_CLK_DIV_RATIO_OFFSET;
> +
> + return parent_rate / cpu_clkdiv_ratio;
> +}
> +
> +static int ap_cpu_clk_set_rate(struct clk_hw *hw, unsigned long rate,
> + unsigned long parent_rate)
> +{
> + struct ap_cpu_clk *clk = to_clk(hw);
> + int reg, divider = parent_rate / rate;
> + unsigned int cpu_clkdiv_reg, cpu_force_reg, cpu_ratio_reg;
> +
> + cpu_clkdiv_reg = AP806_CA72MP2_0_PLL_CR_0_REG_OFFSET +
> + (clk->cluster * AP806_CA72MP2_0_PLL_CR_CLUSTER_OFFSET);
> + cpu_force_reg = AP806_CA72MP2_0_PLL_CR_1_REG_OFFSET +
> + (clk->cluster * AP806_CA72MP2_0_PLL_CR_CLUSTER_OFFSET);
> + cpu_ratio_reg = AP806_CA72MP2_0_PLL_CR_2_REG_OFFSET +
> + (clk->cluster * AP806_CA72MP2_0_PLL_CR_CLUSTER_OFFSET);
> +
> + /* 1. Set CPU divider */
> + regmap_update_bits(clk->pll_cr_base, cpu_clkdiv_reg,
> + AP806_PLL_CR_0_CPU_CLK_DIV_RATIO_MASK, divider);
> +
> + /* 2. Set Reload force */
> + regmap_update_bits(clk->pll_cr_base, cpu_force_reg,
> + AP806_PLL_CR_0_CPU_CLK_RELOAD_FORCE_MASK,
> + AP806_PLL_CR_0_CPU_CLK_RELOAD_FORCE_MASK);
> +
> + /* 3. Set Reload ratio */
> + regmap_update_bits(clk->pll_cr_base, cpu_ratio_reg,
> + BIT(AP806_PLL_CR_0_CPU_CLK_RELOAD_RATIO_OFFSET),
> + BIT(AP806_PLL_CR_0_CPU_CLK_RELOAD_RATIO_OFFSET));
> +
> +
> + /* 4. Wait for stabilizing CPU Clock */
> + do {
> + regmap_read(clk->pll_cr_base,
> + AP806_CA72MP2_0_PLL_SR_REG_OFFSET,
> + &reg);
> + } while (!(reg & BIT(clk->cluster * AP806_CA72MP2_0_PLL_RATIO_STATE)));

Use regmap_read_poll_timeout() API here and give some large timeout
value so that we don't get stuck waiting here forever?

> +
> + /* 5. Clear Reload ratio */

I'm not sure we really need these comments. They're just saying what the
code is doing, so they don't add much value.

> + regmap_update_bits(clk->pll_cr_base, cpu_ratio_reg,
> + BIT(AP806_PLL_CR_0_CPU_CLK_RELOAD_RATIO_OFFSET), 0);
> +
> + return 0;
> +}
> +
> +
> +static long ap_cpu_clk_round_rate(struct clk_hw *hw, unsigned long rate,
> + unsigned long *parent_rate)
> +{
> + int divider = *parent_rate / rate;
> +
> + if (divider > APN806_MAX_DIVIDER)
> + divider = APN806_MAX_DIVIDER;

divider = min(divider, APN806_MAX_DIVIDER);

> +
> + return *parent_rate / divider;
> +}
> +
> +static const struct clk_ops ap_cpu_clk_ops = {
> + .recalc_rate = ap_cpu_clk_recalc_rate,
> + .round_rate = ap_cpu_clk_round_rate,
> + .set_rate = ap_cpu_clk_set_rate,
> +};
> +
> +static int ap_cpu_clock_probe(struct platform_device *pdev)
> +{
> + int ret, nclusters = 0, cluster_index = 0;
> + struct device *dev = &pdev->dev;
> + struct device_node *dn, *np = dev->of_node;
> + struct ap_cpu_clk *ap_cpu_clk;
> + struct regmap *regmap;
> +
> + regmap = syscon_node_to_regmap(np->parent);

Can we just call dev_get_remap() on pdev->dev.parent?

> + if (IS_ERR(regmap)) {
> + pr_err("cannot get pll_cr_base regmap\n");
> + return PTR_ERR(regmap);
> + }
> +
> + /*
> + * AP806 has 4 cpus and DFS for AP806 is controlled per
> + * cluster (2 CPUs per cluster), cpu0 and cpu1 are fixed to
> + * cluster0 while cpu2 and cpu3 are fixed to cluster1 whether
> + * they are enabled or not. Since cpu0 is the boot cpu, then
> + * cluster0 must exist. If cpu2 or cpu3 is enabled, cluster1
> + * will exist and the cluster number is 2; otherwise the
> + * cluster number is 1.
> + */
> + nclusters = 1;
> + for_each_node_by_type(dn, "cpu") {

Isn't there some sort of for_each_cpu_node() API that can be used here?

> + int cpu, err;
> +
> + err = of_property_read_u32(dn, "reg", &cpu);
> + if (WARN_ON(err))
> + return err;
> +
> + /* If cpu2 or cpu3 is enabled */
> + if ((cpu & APN806_CLUSTER_NUM_MASK)) {
> + nclusters = 2;
> + break;
> + }
> + }
> + /*
> + * DFS for AP806 is controlled per cluster (2 CPUs per cluster),
> + * so allocate structs per cluster
> + */
> + ap_cpu_clk = devm_kcalloc(dev, nclusters, sizeof(*ap_cpu_clk),
> + GFP_KERNEL);
> + if (WARN_ON(!ap_cpu_clk))
> + return -ENOMEM;
> +
> + cluster_clks = devm_kcalloc(dev, nclusters, sizeof(*cluster_clks),
> + GFP_KERNEL);
> + if (WARN_ON(!cluster_clks))

Drop the WARN_ON please. If allocation fails we'll already get a large
stack trace and messages.

> + return -ENOMEM;
> +
> + for_each_node_by_type(dn, "cpu") {
> + char *clk_name = "cpu-cluster-0";
> + struct clk_init_data init;
> + const char *parent_name;
> + struct clk *clk, *parent;
> + int cpu, err;
> +
> + err = of_property_read_u32(dn, "reg", &cpu);
> + if (WARN_ON(err))
> + return err;
> +
> + cluster_index = (cpu & APN806_CLUSTER_NUM_MASK);

Nitpick: Drop useless parenthesis please.

> + cluster_index >>= APN806_CLUSTER_NUM_OFFSET;
> +
> + /* Initialize once for one cluster */
> + if (cluster_clks[cluster_index])
> + continue;
> +
> + parent = of_clk_get(np, cluster_index);
> + if (IS_ERR(parent)) {
> + dev_err(dev, "Could not get the clock parent\n");
> + return -EINVAL;
> + }
> + parent_name = __clk_get_name(parent);
> + clk_name[12] += cluster_index;
> + ap_cpu_clk[cluster_index].clk_name =
> + ap_cp_unique_name(dev, np->parent, clk_name);
> + ap_cpu_clk[cluster_index].cluster = cluster_index;
> + ap_cpu_clk[cluster_index].pll_cr_base = regmap;
> + ap_cpu_clk[cluster_index].hw.init = &init;
> + ap_cpu_clk[cluster_index].dev = dev;
> +
> + init.name = ap_cpu_clk[cluster_index].clk_name;
> + init.ops = &ap_cpu_clk_ops;
> + init.num_parents = 1;
> + init.parent_names = &parent_name;
> + init.flags = CLK_GET_RATE_NOCACHE;

Can you add a comment why we need NOCACHE here? It isn't clear why this
is important.

> +
> + clk = devm_clk_register(dev, &ap_cpu_clk[cluster_index].hw);

Please use the clk_hw based registration APIs.

> + if (IS_ERR(clk))
> + return PTR_ERR(clk);
> +
> + cluster_clks[cluster_index] = clk;
> + }
> +
> + clk_data.clk_num = cluster_index + 1;
> + clk_data.clks = cluster_clks;
> +
> + ret = of_clk_add_provider(np, of_clk_src_onecell_get, &clk_data);

And the clk_hw based provider APIs.

> + if (ret)
> + dev_err(dev, "failed to register OF clock provider\n");
> +
> + return ret;
> +}
> +

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