Re: [PATCH 03/16] clk: sunxi-ng: Add fixed factor clock support

Chen-Yu Tsai
2016-05-09T10:05:20Z

Hi,

On Mon, May 9, 2016 at 4:01 AM, Maxime Ripard
<maxime.ripard@free-electrons.com> wrote:
> Some clocks in the Allwinner SoCs clock units are direct, fixed,
> multipliers or dividers from their parent.
>
> Add support for such clocks.
>
> Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
> ---
> drivers/clk/sunxi-ng/Makefile | 2 ++
> drivers/clk/sunxi-ng/ccu_fixed_factor.c | 42 +++++++++++++++++++++++++++
> drivers/clk/sunxi-ng/ccu_fixed_factor.h | 50 +++++++++++++++++++++++++++++++++
> 3 files changed, 94 insertions(+)
> create mode 100644 drivers/clk/sunxi-ng/ccu_fixed_factor.c
> create mode 100644 drivers/clk/sunxi-ng/ccu_fixed_factor.h
>
> diff --git a/drivers/clk/sunxi-ng/Makefile b/drivers/clk/sunxi-ng/Makefile
> index bd3461b0f38c..d76276736765 100644
> --- a/drivers/clk/sunxi-ng/Makefile
> +++ b/drivers/clk/sunxi-ng/Makefile
> @@ -1,2 +1,4 @@
> obj-y += ccu_common.o
> obj-y += ccu_reset.o
> +
> +obj-y += ccu_fixed_factor.o
> diff --git a/drivers/clk/sunxi-ng/ccu_fixed_factor.c b/drivers/clk/sunxi-ng/ccu_fixed_factor.c
> new file mode 100644
> index 000000000000..75df8a854db5
> --- /dev/null
> +++ b/drivers/clk/sunxi-ng/ccu_fixed_factor.c
> @@ -0,0 +1,42 @@
> +/*
> + * Copyright (C) 2016 Maxime Ripard
> + * Maxime Ripard <maxime.ripard@free-electrons.com>
> + *
> + * This program is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU General Public License as
> + * published by the Free Software Foundation; either version 2 of
> + * the License, or (at your option) any later version.
> + */
> +
> +#include <linux/clk-provider.h>
> +
> +#include "ccu_fixed_factor.h"
> +
> +static unsigned long ccu_fixed_factor_recalc_rate(struct clk_hw *hw,
> + unsigned long parent_rate)
> +{
> + struct ccu_fixed_factor *fix = hw_to_ccu_fixed_factor(hw);
> +
> + return parent_rate * fix->mult / fix->div;

do_div (from include/asm-generic/div64.h) is better, since this is an
64 bit value.

> +}
> +
> +static long ccu_fixed_factor_round_rate(struct clk_hw *hw,
> + unsigned long rate,
> + unsigned long *parent_rate)
> +{
> + struct ccu_fixed_factor *fix = hw_to_ccu_fixed_factor(hw);
> +
> + return *parent_rate / fix->div * fix->mult;

Why is this the other way around? With integer math it shouldn't be
interchangeable. (Though it seems clk_fixed_factor does the same...)

Also, clk_fixed_factor handles CLK_SET_RATE_PARENT. Do we need to do the
same here?

> +}
> +
> +static int ccu_fixed_factor_set_rate(struct clk_hw *hw, unsigned long rate,
> + unsigned long parent_rate)
> +{
> + return 0;
> +}
> +
> +const struct clk_ops ccu_fixed_factor_ops = {
> + .recalc_rate = ccu_fixed_factor_recalc_rate,
> + .round_rate = ccu_fixed_factor_round_rate,
> + .set_rate = ccu_fixed_factor_set_rate,
> +};
> diff --git a/drivers/clk/sunxi-ng/ccu_fixed_factor.h b/drivers/clk/sunxi-ng/ccu_fixed_factor.h
> new file mode 100644
> index 000000000000..4e53dbc9d10b
> --- /dev/null
> +++ b/drivers/clk/sunxi-ng/ccu_fixed_factor.h
> @@ -0,0 +1,50 @@
> +/*
> + * Copyright (c) 2016 Maxime Ripard. All rights reserved.
> + *
> + * This software is licensed under the terms of the GNU General Public
> + * License version 2, as published by the Free Software Foundation, and
> + * may be copied, distributed, and modified under those terms.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
> + * GNU General Public License for more details.
> + */
> +
> +#ifndef _CCU_FIXED_FACTOR_H_
> +#define _CCU_FIXED_FACTOR_H_
> +
> +#include <linux/clk-provider.h>
> +
> +#include "ccu_common.h"
> +
> +struct ccu_fixed_factor {
> + u16 div;
> + u16 mult;
> +
> + struct ccu_common common;
> +};
> +
> +#define SUNXI_CCU_FIXED_FACTOR(_struct, _name, _parent, \
> + _div, _mult, _flags) \
> + struct ccu_fixed_factor _struct = { \
> + .div = _div, \
> + .mult = _mult, \
> + .common = { \
> + .hw.init = SUNXI_HW_INIT(_name, \
> + _parent, \
> + &ccu_fixed_factor_ops, \
> + _flags), \
> + }, \
> + }
> +
> +static inline struct ccu_fixed_factor *hw_to_ccu_fixed_factor(struct clk_hw *hw)
> +{
> + struct ccu_common *common = hw_to_ccu_common(hw);
> +
> + return container_of(common, struct ccu_fixed_factor, common);
> +}
> +
> +extern const struct clk_ops ccu_fixed_factor_ops;
> +
> +#endif /* _CCU_FIXED_FACTOR_H_ */
> --
> 2.8.2
>

Regards
ChenYu