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Date:   Thu, 2 Nov 2017 18:11:05 +0000
From:   Julien Thierry <julien.thierry@....com>
To:     Chunyan Zhang <chunyan.zhang@...eadtrum.com>,
        Stephen Boyd <sboyd@...eaurora.org>,
        Michael Turquette <mturquette@...libre.com>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>
Cc:     Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>, linux-clk@...r.kernel.org,
        devicetree@...r.kernel.org, Arnd Bergmann <arnd@...db.de>,
        Mark Brown <broonie@...nel.org>,
        Xiaolong Zhang <xiaolong.zhang@...eadtrum.com>,
        Ben Li <ben.li@...eadtrum.com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Orson Zhai <orson.zhai@...eadtrum.com>,
        Chunyan Zhang <zhang.lyra@...il.com>
Subject: Re: [PATCH V3 05/11] clk: sprd: add mux clock support

Hi,

On 02/11/17 06:56, Chunyan Zhang wrote:
> This patch adds clock multiplexor support for Spreadtrum platforms,
> the mux clocks also can be found in sprd composite clocks, so
> provides two helpers that can be reused later on.
> 
> Signed-off-by: Chunyan Zhang <chunyan.zhang@...eadtrum.com>
> ---
>   drivers/clk/sprd/Makefile |  1 +
>   drivers/clk/sprd/mux.c    | 89 +++++++++++++++++++++++++++++++++++++++++++++++
>   drivers/clk/sprd/mux.h    | 65 ++++++++++++++++++++++++++++++++++
>   3 files changed, 155 insertions(+)
>   create mode 100644 drivers/clk/sprd/mux.c
>   create mode 100644 drivers/clk/sprd/mux.h
> 
> diff --git a/drivers/clk/sprd/Makefile b/drivers/clk/sprd/Makefile
> index 8cd5592..cee36b5 100644
> --- a/drivers/clk/sprd/Makefile
> +++ b/drivers/clk/sprd/Makefile
> @@ -2,3 +2,4 @@ obj-$(CONFIG_SPRD_COMMON_CLK)	+= clk-sprd.o
>   
>   clk-sprd-y	+= common.o
>   clk-sprd-y	+= gate.o
> +clk-sprd-y	+= mux.o
> diff --git a/drivers/clk/sprd/mux.c b/drivers/clk/sprd/mux.c
> new file mode 100644
> index 0000000..5a344e0
> --- /dev/null
> +++ b/drivers/clk/sprd/mux.c
> @@ -0,0 +1,89 @@
> +/*
> + * Spreadtrum multiplexer clock driver
> + *
> + * Copyright (C) 2017 Spreadtrum, Inc.
> + * Author: Chunyan Zhang <chunyan.zhang@...eadtrum.com>
> + *
> + * SPDX-License-Identifier: GPL-2.0
> + */
> +
> +#include <linux/clk.h>
> +#include <linux/clk-provider.h>
> +#include <linux/regmap.h>
> +
> +#include "mux.h"
> +
> +DEFINE_SPINLOCK(sprd_mux_lock);
> +EXPORT_SYMBOL_GPL(sprd_mux_lock);
> +
> +u8 sprd_mux_helper_get_parent(const struct sprd_clk_common *common,
> +			      const struct sprd_mux_internal *mux)
> +{
> +	unsigned int reg;
> +	u8 parent;
> +	int num_parents;
> +	int i;
> +
> +	sprd_regmap_read(common->regmap, common->reg, &reg);
> +	parent = reg >> mux->shift;
> +	parent &= (1 << mux->width) - 1;
> +
> +	if (mux->table) {
> +		num_parents = clk_hw_get_num_parents(&common->hw);
> +
> +		for (i = 0; i < num_parents; i++)
> +			if (parent == mux->table[i] ||
> +			    (i < (num_parents - 1) && parent > mux->table[i] &&
> +			     parent < mux->table[i + 1]))
> +				return i;
> +		if (i == num_parents)
> +			return i - 1;

The if branch is not necessary since you only get there when the loop 
has finished, so the condition is always true. And the loop can be 
simplified to:

for (i = 0; i < num_parents - 1; i++)
	if (parent >= mux->table[i] &&  parent < mux->table[i + 1])
		return i;

return num_parents;


> +	}
> +
> +	return parent;
> +}
> +EXPORT_SYMBOL_GPL(sprd_mux_helper_get_parent);
> +
> +static u8 sprd_mux_get_parent(struct clk_hw *hw)
> +{
> +	struct sprd_mux *cm = hw_to_sprd_mux(hw);
> +
> +	return sprd_mux_helper_get_parent(&cm->common, &cm->mux);
> +}
> +
> +int sprd_mux_helper_set_parent(const struct sprd_clk_common *common,
> +			       const struct sprd_mux_internal *mux,
> +			       u8 index)
> +{
> +	unsigned long flags = 0;
> +	unsigned int reg;
> +
> +	if (mux->table)
> +		index = mux->table[index];
> +
> +	spin_lock_irqsave(common->lock, flags);
> +
> +	sprd_regmap_read(common->regmap, common->reg, &reg);
> +	reg &= ~GENMASK(mux->width + mux->shift - 1, mux->shift);
> +	sprd_regmap_write(common->regmap, common->reg,
> +			  reg | (index << mux->shift));
> +
> +	spin_unlock_irqrestore(common->lock, flags);
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(sprd_mux_helper_set_parent);
> +
> +static int sprd_mux_set_parent(struct clk_hw *hw, u8 index)
> +{
> +	struct sprd_mux *cm = hw_to_sprd_mux(hw);
> +
> +	return sprd_mux_helper_set_parent(&cm->common, &cm->mux, index);
> +}
> +
> +const struct clk_ops sprd_mux_ops = {
> +	.get_parent = sprd_mux_get_parent,
> +	.set_parent = sprd_mux_set_parent,
> +	.determine_rate = __clk_mux_determine_rate,
> +};
> +EXPORT_SYMBOL_GPL(sprd_mux_ops);

Same as with the other patch, I'd recommend have one set of ops for 
direct mux and another one for a mux using a table to map the parents. 
Keeping functions for both modes separate.

Cheers,

> diff --git a/drivers/clk/sprd/mux.h b/drivers/clk/sprd/mux.h
> new file mode 100644
> index 0000000..148ca8c
> --- /dev/null
> +++ b/drivers/clk/sprd/mux.h
> @@ -0,0 +1,65 @@
> +/*
> + * Spreadtrum multiplexer clock driver
> + *
> + * Copyright (C) 2017 Spreadtrum, Inc.
> + * Author: Chunyan Zhang <chunyan.zhang@...eadtrum.com>
> + *
> + * SPDX-License-Identifier: GPL-2.0
> + */
> +
> +#ifndef _SPRD_MUX_H_
> +#define _SPRD_MUX_H_
> +
> +#include "common.h"
> +
> +struct sprd_mux_internal {
> +	u8		shift;
> +	u8		width;
> +	const u8	*table;
> +};
> +
> +struct sprd_mux {
> +	struct sprd_mux_internal mux;
> +	struct sprd_clk_common	common;
> +};
> +
> +#define _SPRD_MUX_CLK(_shift, _width, _table)		\
> +	{						\
> +		.shift	= _shift,			\
> +		.width	= _width,			\
> +		.table	= _table,			\
> +	}
> +
> +#define SPRD_MUX_CLK(_struct, _name, _parents, _table,			\
> +				     _reg, _shift, _width,		\
> +				     _flags)				\
> +	struct sprd_mux _struct = {					\
> +		.mux	= _SPRD_MUX_CLK(_shift, _width, _table),	\
> +		.common	= {						\
> +			.regmap		= NULL,				\
> +			.reg		= _reg,				\
> +			.lock		= &sprd_mux_lock,		\
> +			.hw.init = CLK_HW_INIT_PARENTS(_name,		\
> +						       _parents,	\
> +						       &sprd_mux_ops,	\
> +						       _flags),		\
> +		}							\
> +	}
> +
> +static inline struct sprd_mux *hw_to_sprd_mux(const struct clk_hw *hw)
> +{
> +	struct sprd_clk_common *common = hw_to_sprd_clk_common(hw);
> +
> +	return container_of(common, struct sprd_mux, common);
> +}
> +
> +extern const struct clk_ops sprd_mux_ops;
> +extern spinlock_t sprd_mux_lock;
> +
> +u8 sprd_mux_helper_get_parent(const struct sprd_clk_common *common,
> +			      const struct sprd_mux_internal *mux);
> +int sprd_mux_helper_set_parent(const struct sprd_clk_common *common,
> +			       const struct sprd_mux_internal *mux,
> +			       u8 index);
> +
> +#endif /* _SPRD_MUX_H_ */
> 

-- 
Julien Thierry

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