164 lines
3.7 KiB
C
164 lines
3.7 KiB
C
/*
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* Copyright (C) 2012 ST Microelectronics
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* Viresh Kumar <vireshk@kernel.org>
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*
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* This file is licensed under the terms of the GNU General Public
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* License version 2. This program is licensed "as is" without any
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* warranty of any kind, whether express or implied.
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*
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* Fractional Synthesizer clock implementation
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*/
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#define pr_fmt(fmt) "clk-frac-synth: " fmt
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#include <linux/clk-provider.h>
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#include <linux/slab.h>
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#include <linux/io.h>
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#include <linux/err.h>
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#include "clk.h"
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#define DIV_FACTOR_MASK 0x1FFFF
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/*
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* DOC: Fractional Synthesizer clock
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*
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* Fout from synthesizer can be given from below equation:
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*
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* Fout= Fin/2*div (division factor)
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* div is 17 bits:-
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* 0-13 (fractional part)
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* 14-16 (integer part)
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* div is (16-14 bits).(13-0 bits) (in binary)
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*
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* Fout = Fin/(2 * div)
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* Fout = ((Fin / 10000)/(2 * div)) * 10000
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* Fout = (2^14 * (Fin / 10000)/(2^14 * (2 * div))) * 10000
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* Fout = (((Fin / 10000) << 14)/(2 * (div << 14))) * 10000
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*
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* div << 14 simply 17 bit value written at register.
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* Max error due to scaling down by 10000 is 10 KHz
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*/
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#define to_clk_frac(_hw) container_of(_hw, struct clk_frac, hw)
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static unsigned long frac_calc_rate(struct clk_hw *hw, unsigned long prate,
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int index)
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{
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struct clk_frac *frac = to_clk_frac(hw);
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struct frac_rate_tbl *rtbl = frac->rtbl;
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prate /= 10000;
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prate <<= 14;
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prate /= (2 * rtbl[index].div);
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prate *= 10000;
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return prate;
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}
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static long clk_frac_round_rate(struct clk_hw *hw, unsigned long drate,
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unsigned long *prate)
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{
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struct clk_frac *frac = to_clk_frac(hw);
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int unused;
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return clk_round_rate_index(hw, drate, *prate, frac_calc_rate,
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frac->rtbl_cnt, &unused);
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}
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static unsigned long clk_frac_recalc_rate(struct clk_hw *hw,
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unsigned long parent_rate)
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{
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struct clk_frac *frac = to_clk_frac(hw);
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unsigned long flags = 0;
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unsigned int div = 1, val;
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if (frac->lock)
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spin_lock_irqsave(frac->lock, flags);
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val = readl_relaxed(frac->reg);
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if (frac->lock)
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spin_unlock_irqrestore(frac->lock, flags);
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div = val & DIV_FACTOR_MASK;
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if (!div)
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return 0;
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parent_rate = parent_rate / 10000;
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parent_rate = (parent_rate << 14) / (2 * div);
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return parent_rate * 10000;
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}
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/* Configures new clock rate of frac */
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static int clk_frac_set_rate(struct clk_hw *hw, unsigned long drate,
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unsigned long prate)
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{
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struct clk_frac *frac = to_clk_frac(hw);
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struct frac_rate_tbl *rtbl = frac->rtbl;
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unsigned long flags = 0, val;
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int i;
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clk_round_rate_index(hw, drate, prate, frac_calc_rate, frac->rtbl_cnt,
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&i);
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if (frac->lock)
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spin_lock_irqsave(frac->lock, flags);
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val = readl_relaxed(frac->reg) & ~DIV_FACTOR_MASK;
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val |= rtbl[i].div & DIV_FACTOR_MASK;
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writel_relaxed(val, frac->reg);
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if (frac->lock)
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spin_unlock_irqrestore(frac->lock, flags);
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return 0;
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}
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static const struct clk_ops clk_frac_ops = {
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.recalc_rate = clk_frac_recalc_rate,
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.round_rate = clk_frac_round_rate,
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.set_rate = clk_frac_set_rate,
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};
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struct clk *clk_register_frac(const char *name, const char *parent_name,
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unsigned long flags, void __iomem *reg,
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struct frac_rate_tbl *rtbl, u8 rtbl_cnt, spinlock_t *lock)
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{
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struct clk_init_data init;
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struct clk_frac *frac;
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struct clk *clk;
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if (!name || !parent_name || !reg || !rtbl || !rtbl_cnt) {
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pr_err("Invalid arguments passed\n");
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return ERR_PTR(-EINVAL);
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}
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frac = kzalloc(sizeof(*frac), GFP_KERNEL);
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if (!frac)
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return ERR_PTR(-ENOMEM);
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/* struct clk_frac assignments */
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frac->reg = reg;
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frac->rtbl = rtbl;
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frac->rtbl_cnt = rtbl_cnt;
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frac->lock = lock;
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frac->hw.init = &init;
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init.name = name;
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init.ops = &clk_frac_ops;
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init.flags = flags;
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init.parent_names = &parent_name;
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init.num_parents = 1;
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clk = clk_register(NULL, &frac->hw);
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if (!IS_ERR_OR_NULL(clk))
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return clk;
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pr_err("clk register failed\n");
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kfree(frac);
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return NULL;
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}
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