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* Copyright (c) 2014 MundoReader S.L.
* Author: Heiko Stuebner <>
* based on clk/samsung/clk-cpu.c
* Copyright (c) 2014 Samsung Electronics Co., Ltd.
* Author: Thomas Abraham <>
* 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.
* A CPU clock is defined as a clock supplied to a CPU or a group of CPUs.
* The CPU clock is typically derived from a hierarchy of clock
* blocks which includes mux and divider blocks. There are a number of other
* auxiliary clocks supplied to the CPU domain such as the debug blocks and AXI
* clock for CPU domain. The rates of these auxiliary clocks are related to the
* CPU clock rate and this relation is usually specified in the hardware manual
* of the SoC or supplied after the SoC characterization.
* The below implementation of the CPU clock allows the rate changes of the CPU
* clock and the corresponding rate changes of the auxillary clocks of the CPU
* domain. The platform clock driver provides a clock register configuration
* for each configurable rate which is then used to program the clock hardware
* registers to acheive a fast co-oridinated rate change for all the CPU domain
* clocks.
* On a rate change request for the CPU clock, the rate change is propagated
* upto the PLL supplying the clock to the CPU domain clock blocks. While the
* CPU domain PLL is reconfigured, the CPU domain clocks are driven using an
* alternate clock source. If required, the alternate clock source is divided
* down in order to keep the output clock rate within the previous OPP limits.
#include <linux/of.h>
#include <linux/slab.h>
#include <linux/io.h>
#include <linux/clk-provider.h>
#include "clk.h"
* struct rockchip_cpuclk: information about clock supplied to a CPU core.
* @hw: handle between ccf and cpu clock.
* @alt_parent: alternate parent clock to use when switching the speed
* of the primary parent clock.
* @reg_base: base register for cpu-clock values.
* @clk_nb: clock notifier registered for changes in clock speed of the
* primary parent clock.
* @rate_count: number of rates in the rate_table
* @rate_table: pll-rates and their associated dividers
* @reg_data: cpu-specific register settings
* @lock: clock lock
struct rockchip_cpuclk {
struct clk_hw hw;
struct clk_mux cpu_mux;
const struct clk_ops *cpu_mux_ops;
struct clk *alt_parent;
void __iomem *reg_base;
struct notifier_block clk_nb;
unsigned int rate_count;
struct rockchip_cpuclk_rate_table *rate_table;
const struct rockchip_cpuclk_reg_data *reg_data;
spinlock_t *lock;
#define to_rockchip_cpuclk_hw(hw) container_of(hw, struct rockchip_cpuclk, hw)
#define to_rockchip_cpuclk_nb(nb) \
container_of(nb, struct rockchip_cpuclk, clk_nb)
static const struct rockchip_cpuclk_rate_table *rockchip_get_cpuclk_settings(
struct rockchip_cpuclk *cpuclk, unsigned long rate)
const struct rockchip_cpuclk_rate_table *rate_table =
int i;
for (i = 0; i < cpuclk->rate_count; i++) {
if (rate == rate_table[i].prate)
return &rate_table[i];
return NULL;
static unsigned long rockchip_cpuclk_recalc_rate(struct clk_hw *hw,
unsigned long parent_rate)
struct rockchip_cpuclk *cpuclk = to_rockchip_cpuclk_hw(hw);
const struct rockchip_cpuclk_reg_data *reg_data = cpuclk->reg_data;
u32 clksel0 = readl_relaxed(cpuclk->reg_base + reg_data->core_reg);
clksel0 >>= reg_data->div_core_shift;
clksel0 &= reg_data->div_core_mask;
return parent_rate / (clksel0 + 1);
static const struct clk_ops rockchip_cpuclk_ops = {
.recalc_rate = rockchip_cpuclk_recalc_rate,
static void rockchip_cpuclk_set_dividers(struct rockchip_cpuclk *cpuclk,
const struct rockchip_cpuclk_rate_table *rate)
int i;
/* alternate parent is active now. set the dividers */
for (i = 0; i < ARRAY_SIZE(rate->divs); i++) {
const struct rockchip_cpuclk_clksel *clksel = &rate->divs[i];
if (!clksel->reg)
pr_debug("%s: setting reg 0x%x to 0x%x\n",
__func__, clksel->reg, clksel->val);
writel(clksel->val , cpuclk->reg_base + clksel->reg);
static int rockchip_cpuclk_pre_rate_change(struct rockchip_cpuclk *cpuclk,
struct clk_notifier_data *ndata)
const struct rockchip_cpuclk_reg_data *reg_data = cpuclk->reg_data;
unsigned long alt_prate, alt_div;
unsigned long flags;
alt_prate = clk_get_rate(cpuclk->alt_parent);
spin_lock_irqsave(cpuclk->lock, flags);
* If the old parent clock speed is less than the clock speed
* of the alternate parent, then it should be ensured that at no point
* the armclk speed is more than the old_rate until the dividers are
* set.
if (alt_prate > ndata->old_rate) {
/* calculate dividers */
alt_div = DIV_ROUND_UP(alt_prate, ndata->old_rate) - 1;
if (alt_div > reg_data->div_core_mask) {
pr_warn("%s: limiting alt-divider %lu to %d\n",
__func__, alt_div, reg_data->div_core_mask);
alt_div = reg_data->div_core_mask;
* Change parents and add dividers in a single transaction.
* NOTE: we do this in a single transaction so we're never
* dividing the primary parent by the extra dividers that were
* needed for the alt.
pr_debug("%s: setting div %lu as alt-rate %lu > old-rate %lu\n",
__func__, alt_div, alt_prate, ndata->old_rate);
writel(HIWORD_UPDATE(alt_div, reg_data->div_core_mask,
reg_data->div_core_shift) |
HIWORD_UPDATE(1, 1, reg_data->mux_core_shift),
cpuclk->reg_base + reg_data->core_reg);
} else {
/* select alternate parent */
writel(HIWORD_UPDATE(1, 1, reg_data->mux_core_shift),
cpuclk->reg_base + reg_data->core_reg);
spin_unlock_irqrestore(cpuclk->lock, flags);
return 0;
static int rockchip_cpuclk_post_rate_change(struct rockchip_cpuclk *cpuclk,
struct clk_notifier_data *ndata)
const struct rockchip_cpuclk_reg_data *reg_data = cpuclk->reg_data;
const struct rockchip_cpuclk_rate_table *rate;
unsigned long flags;
rate = rockchip_get_cpuclk_settings(cpuclk, ndata->new_rate);
if (!rate) {
pr_err("%s: Invalid rate : %lu for cpuclk\n",
__func__, ndata->new_rate);
return -EINVAL;
spin_lock_irqsave(cpuclk->lock, flags);
if (ndata->old_rate < ndata->new_rate)
rockchip_cpuclk_set_dividers(cpuclk, rate);
* post-rate change event, re-mux to primary parent and remove dividers.
* NOTE: we do this in a single transaction so we're never dividing the
* primary parent by the extra dividers that were needed for the alt.
writel(HIWORD_UPDATE(0, reg_data->div_core_mask,
reg_data->div_core_shift) |
HIWORD_UPDATE(0, 1, reg_data->mux_core_shift),
cpuclk->reg_base + reg_data->core_reg);
if (ndata->old_rate > ndata->new_rate)
rockchip_cpuclk_set_dividers(cpuclk, rate);
spin_unlock_irqrestore(cpuclk->lock, flags);
return 0;
* This clock notifier is called when the frequency of the parent clock
* of cpuclk is to be changed. This notifier handles the setting up all
* the divider clocks, remux to temporary parent and handling the safe
* frequency levels when using temporary parent.
static int rockchip_cpuclk_notifier_cb(struct notifier_block *nb,
unsigned long event, void *data)
struct clk_notifier_data *ndata = data;
struct rockchip_cpuclk *cpuclk = to_rockchip_cpuclk_nb(nb);
int ret = 0;
pr_debug("%s: event %lu, old_rate %lu, new_rate: %lu\n",
__func__, event, ndata->old_rate, ndata->new_rate);
if (event == PRE_RATE_CHANGE)
ret = rockchip_cpuclk_pre_rate_change(cpuclk, ndata);
else if (event == POST_RATE_CHANGE)
ret = rockchip_cpuclk_post_rate_change(cpuclk, ndata);
return notifier_from_errno(ret);
struct clk *rockchip_clk_register_cpuclk(const char *name,
const char *const *parent_names, u8 num_parents,
const struct rockchip_cpuclk_reg_data *reg_data,
const struct rockchip_cpuclk_rate_table *rates,
int nrates, void __iomem *reg_base, spinlock_t *lock)
struct rockchip_cpuclk *cpuclk;
struct clk_init_data init;
struct clk *clk, *cclk;
int ret;
if (num_parents != 2) {
pr_err("%s: needs two parent clocks\n", __func__);
return ERR_PTR(-EINVAL);
cpuclk = kzalloc(sizeof(*cpuclk), GFP_KERNEL);
if (!cpuclk)
return ERR_PTR(-ENOMEM); = name;
init.parent_names = &parent_names[0];
init.num_parents = 1;
init.ops = &rockchip_cpuclk_ops;
/* only allow rate changes when we have a rate table */
init.flags = (nrates > 0) ? CLK_SET_RATE_PARENT : 0;
/* disallow automatic parent changes by ccf */
init.flags |= CLK_GET_RATE_NOCACHE;
cpuclk->reg_base = reg_base;
cpuclk->lock = lock;
cpuclk->reg_data = reg_data;
cpuclk->clk_nb.notifier_call = rockchip_cpuclk_notifier_cb;
cpuclk->hw.init = &init;
cpuclk->alt_parent = __clk_lookup(parent_names[1]);
if (!cpuclk->alt_parent) {
pr_err("%s: could not lookup alternate parent\n",
ret = -EINVAL;
goto free_cpuclk;
ret = clk_prepare_enable(cpuclk->alt_parent);
if (ret) {
pr_err("%s: could not enable alternate parent\n",
goto free_cpuclk;
clk = __clk_lookup(parent_names[0]);
if (!clk) {
pr_err("%s: could not lookup parent clock %s\n",
__func__, parent_names[0]);
ret = -EINVAL;
goto free_cpuclk;
ret = clk_notifier_register(clk, &cpuclk->clk_nb);
if (ret) {
pr_err("%s: failed to register clock notifier for %s\n",
__func__, name);
goto free_cpuclk;
if (nrates > 0) {
cpuclk->rate_count = nrates;
cpuclk->rate_table = kmemdup(rates,
sizeof(*rates) * nrates,
if (!cpuclk->rate_table) {
pr_err("%s: could not allocate memory for cpuclk rates\n",
ret = -ENOMEM;
goto unregister_notifier;
cclk = clk_register(NULL, &cpuclk->hw);
if (IS_ERR(clk)) {
pr_err("%s: could not register cpuclk %s\n", __func__, name);
ret = PTR_ERR(clk);
goto free_rate_table;
return cclk;
clk_notifier_unregister(clk, &cpuclk->clk_nb);
return ERR_PTR(ret);