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Date:	Wed, 08 Jan 2014 18:11:40 -0800
From:	Stephen Boyd <sboyd@...eaurora.org>
To:	Mike Turquette <mturquette@...aro.org>
CC:	linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	Saravana Kannan <skannan@...eaurora.org>,
	Mark Brown <broonie@...nel.org>
Subject: Re: [PATCH v4 02/15] clk: Allow drivers to pass in a regmap

On 01/08/14 17:51, Mike Turquette wrote:
> Quoting Stephen Boyd (2013-12-23 17:12:26)
>> Add support to the clock core so that drivers can pass in a
>> regmap. If no regmap is specified try to query the device that's
>> registering the clock for its regmap. This should allow drivers
>> to use the core regmap helpers. This is based on a similar design
>> in the regulator framework.
>>
>> Cc: Mark Brown <broonie@...nel.org>
>> Signed-off-by: Stephen Boyd <sboyd@...eaurora.org>
>> ---
>>  drivers/clk/clk.c            | 8 ++++++++
>>  include/linux/clk-provider.h | 7 +++++++
>>  2 files changed, 15 insertions(+)
>>
>> diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
>> index 9ad7b71..5e71f5c 100644
>> --- a/drivers/clk/clk.c
>> +++ b/drivers/clk/clk.c
>> @@ -20,6 +20,7 @@
>>  #include <linux/device.h>
>>  #include <linux/init.h>
>>  #include <linux/sched.h>
>> +#include <linux/regmap.h>
>>  
>>  static DEFINE_SPINLOCK(enable_lock);
>>  static DEFINE_MUTEX(prepare_lock);
>> @@ -1834,6 +1835,13 @@ static int _clk_register(struct device *dev, struct clk_hw *hw, struct clk *clk)
>>         clk->num_parents = hw->init->num_parents;
>>         hw->clk = clk;
>>  
>> +       if (hw->init->regmap)
>> +               hw->regmap = hw->init->regmap;
> Hi Stephen,
>
> The whole series looks good to me except for the placement of the regmap
> details inside struct clk_hw. That structure exists only to hide struct
> clk from the hardware-specific clock structure and I'd not like to set
> the precedent of shoving per-clock data into it.
>
> As an alternative, how about finding a way to put these per-clock regmap
> details into the hardware-specific clock structure? I understand that
> you want to make these ops available to others, which is why they are in
> the public struct clk_hw. I'm just wondering if that is the right way to
> do it...

The regulator framework has gone this way. It seemed like a similar
approach in the clock framework would be the right way to go too.

>
> Patch #3 illustrates the sort of struct-member-creep that worries me.
> What is to stop someone from putting "unsigned int divider_reg" or
> "unsigned int mux_reg", and then the thing just keeps growing.
>

I see two ways forward if you don't want these members in struct clk_hw.

1) Inheritance: struct clk_regmap wrapper struct and
clk_register_regmap() and devm_clk_register_regmap() and then another
wrapper struct around that.

 example:

struct clk_regmap {
        struct clk_hw hw;
        struct regmap *regmap;
        unsigned int enable_reg;
        unsigned int enable_mask;
        bool enable_is_inverted;
};

struct clk_branch {
        u32     hwcg_reg;
        u32     halt_reg;
        u8      hwcg_bit;
        u8      halt_bit;
        u8      halt_check;

        struct clk_regmap       clkr;
};

static struct clk_branch gsbi1_uart_clk = {
        .halt_reg = 0x2fcc,
        .halt_bit = 10,
        .clkr = {
                .enable_reg = 0x29d4,
                .enable_mask = BIT(9),
                .hw.init = &(struct clk_init_data){
                        .name = "gsbi1_uart_clk",
                        .parent_names = (const char *[]){
                                "gsbi1_uart_src",
                        },
                        .num_parents = 1,
                        .ops = &clk_branch_ops,
                        .flags = CLK_SET_RATE_PARENT,
                },
        },
};


2) Interfaces: Add a void *data in struct clk_hw that can point to
whatever I want and still have the same clk_regmap_register() and
devm_clk_regmap_register()

Example:

struct clk_hw {
        struct clk *clk;
        const struct clk_init_data *init;
        void *data;
};

struct clk_regmap {
        struct regmap *regmap;
        unsigned int enable_reg;
        unsigned int enable_mask;
        bool enable_is_inverted;
};

struct clk_branch {
        u32     hwcg_reg;
        u32     halt_reg;
        u8      hwcg_bit;
        u8      halt_bit;
        u8      halt_check;

        struct clk_hw;
};

static struct clk_branch gsbi1_uart_clk = {
        .halt_reg = 0x2fcc,
        .halt_bit = 10,
        .hw = {
                .data = &(struct clk_regmap){
                        .enable_reg = 0x29d4,
                        .enable_mask = BIT(9),
                 };
                .init = &(struct clk_init_data){
                        .name = "gsbi1_uart_clk",
                        .parent_names = (const char *[]){
                                "gsbi1_uart_src",
                        },
                        .num_parents = 1,
                        .ops = &clk_branch_ops,
                        .flags = CLK_SET_RATE_PARENT,
                },
        },
};

I guess option 2 is less likely given your comment about clk_hw being
nothing more than a traversal mechanism.

-- 
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hosted by The Linux Foundation

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