From 270b9f421e66ee5d135c99ba1c2b883c7750ab6c Mon Sep 17 00:00:00 2001 From: Viresh Kumar Date: Wed, 11 Apr 2012 18:04:23 +0530 Subject: SPEAr: clk: Add Fractional Synthesizer clock All SPEAr SoC's contain Fractional Synthesizers. Their Fout is derived from following equations: Fout = Fin / (2 * div) (division factor) div is 17 bits:- 0-13 (fractional part) 14-16 (integer part) div is (16-14 bits).(13-0 bits) (in binary) Fout = Fin/(2 * div) Fout = ((Fin / 10000)/(2 * div)) * 10000 Fout = (2^14 * (Fin / 10000)/(2^14 * (2 * div))) * 10000 Fout = (((Fin / 10000) << 14)/(2 * (div << 14))) * 10000 div << 14 is simply 17 bit value written at register. This patch adds in support for this type of clock. Signed-off-by: Viresh Kumar Reviewed-by: Mike Turquette --- drivers/clk/spear/clk-frac-synth.c | 165 +++++++++++++++++++++++++++++++++++++ 1 file changed, 165 insertions(+) create mode 100644 drivers/clk/spear/clk-frac-synth.c (limited to 'drivers/clk/spear/clk-frac-synth.c') diff --git a/drivers/clk/spear/clk-frac-synth.c b/drivers/clk/spear/clk-frac-synth.c new file mode 100644 index 000000000000..4dbdb3fe18e0 --- /dev/null +++ b/drivers/clk/spear/clk-frac-synth.c @@ -0,0 +1,165 @@ +/* + * Copyright (C) 2012 ST Microelectronics + * Viresh Kumar + * + * This file is licensed under the terms of the GNU General Public + * License version 2. This program is licensed "as is" without any + * warranty of any kind, whether express or implied. + * + * Fractional Synthesizer clock implementation + */ + +#define pr_fmt(fmt) "clk-frac-synth: " fmt + +#include +#include +#include +#include +#include "clk.h" + +#define DIV_FACTOR_MASK 0x1FFFF + +/* + * DOC: Fractional Synthesizer clock + * + * Fout from synthesizer can be given from below equation: + * + * Fout= Fin/2*div (division factor) + * div is 17 bits:- + * 0-13 (fractional part) + * 14-16 (integer part) + * div is (16-14 bits).(13-0 bits) (in binary) + * + * Fout = Fin/(2 * div) + * Fout = ((Fin / 10000)/(2 * div)) * 10000 + * Fout = (2^14 * (Fin / 10000)/(2^14 * (2 * div))) * 10000 + * Fout = (((Fin / 10000) << 14)/(2 * (div << 14))) * 10000 + * + * div << 14 simply 17 bit value written at register. + * Max error due to scaling down by 10000 is 10 KHz + */ + +#define to_clk_frac(_hw) container_of(_hw, struct clk_frac, hw) + +static unsigned long frac_calc_rate(struct clk_hw *hw, unsigned long prate, + int index) +{ + struct clk_frac *frac = to_clk_frac(hw); + struct frac_rate_tbl *rtbl = frac->rtbl; + + prate /= 10000; + prate <<= 14; + prate /= (2 * rtbl[index].div); + prate *= 10000; + + return prate; +} + +static long clk_frac_round_rate(struct clk_hw *hw, unsigned long drate, + unsigned long *prate) +{ + struct clk_frac *frac = to_clk_frac(hw); + int unused; + + return clk_round_rate_index(hw, drate, *prate, frac_calc_rate, + frac->rtbl_cnt, &unused); +} + +static unsigned long clk_frac_recalc_rate(struct clk_hw *hw, + unsigned long parent_rate) +{ + struct clk_frac *frac = to_clk_frac(hw); + unsigned long flags = 0; + unsigned int div = 1, val; + + if (frac->lock) + spin_lock_irqsave(frac->lock, flags); + + val = readl_relaxed(frac->reg); + + if (frac->lock) + spin_unlock_irqrestore(frac->lock, flags); + + div = val & DIV_FACTOR_MASK; + + if (!div) + return 0; + + parent_rate = parent_rate / 10000; + + parent_rate = (parent_rate << 14) / (2 * div); + return parent_rate * 10000; +} + +/* Configures new clock rate of frac */ +static int clk_frac_set_rate(struct clk_hw *hw, unsigned long drate, + unsigned long prate) +{ + struct clk_frac *frac = to_clk_frac(hw); + struct frac_rate_tbl *rtbl = frac->rtbl; + unsigned long flags = 0, val; + int i; + + clk_round_rate_index(hw, drate, prate, frac_calc_rate, frac->rtbl_cnt, + &i); + + if (frac->lock) + spin_lock_irqsave(frac->lock, flags); + + val = readl_relaxed(frac->reg) & ~DIV_FACTOR_MASK; + val |= rtbl[i].div & DIV_FACTOR_MASK; + writel_relaxed(val, frac->reg); + + if (frac->lock) + spin_unlock_irqrestore(frac->lock, flags); + + return 0; +} + +struct clk_ops clk_frac_ops = { + .recalc_rate = clk_frac_recalc_rate, + .round_rate = clk_frac_round_rate, + .set_rate = clk_frac_set_rate, +}; + +struct clk *clk_register_frac(const char *name, const char *parent_name, + unsigned long flags, void __iomem *reg, + struct frac_rate_tbl *rtbl, u8 rtbl_cnt, spinlock_t *lock) +{ + struct clk_init_data init; + struct clk_frac *frac; + struct clk *clk; + + if (!name || !parent_name || !reg || !rtbl || !rtbl_cnt) { + pr_err("Invalid arguments passed"); + return ERR_PTR(-EINVAL); + } + + frac = kzalloc(sizeof(*frac), GFP_KERNEL); + if (!frac) { + pr_err("could not allocate frac clk\n"); + return ERR_PTR(-ENOMEM); + } + + /* struct clk_frac assignments */ + frac->reg = reg; + frac->rtbl = rtbl; + frac->rtbl_cnt = rtbl_cnt; + frac->lock = lock; + frac->hw.init = &init; + + init.name = name; + init.ops = &clk_frac_ops; + init.flags = flags; + init.parent_names = &parent_name; + init.num_parents = 1; + + clk = clk_register(NULL, &frac->hw); + if (!IS_ERR_OR_NULL(clk)) + return clk; + + pr_err("clk register failed\n"); + kfree(frac); + + return NULL; +} -- cgit v1.2.3