linux-kernel - Re: [PATCH V3 05/11] clk: sprd: add mux clock support

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Date:   Thu, 2 Nov 2017 18:22:22 +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



On 02/11/17 18:11, Julien Thierry wrote:
> 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;

Oops, meant to say "return num_parents - 1;" on that last line.

-- 
Julien Thierry