linux-kernel - Re: [PATCH V2] clk: Add composite clock type

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Date:	Wed, 6 Feb 2013 15:22:54 +0530
From:	Prashant Gaikwad <pgaikwad@...dia.com>
To:	Hiroshi Doyu <hdoyu@...dia.com>
CC:	"mturquette@...aro.org" <mturquette@...aro.org>,
	"sboyd@...eaurora.org" <sboyd@...eaurora.org>,
	"swarren@...dotorg.org" <swarren@...dotorg.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
	"t.figa@...sung.com" <t.figa@...sung.com>
Subject: Re: [PATCH V2] clk: Add composite clock type

On Wednesday 06 February 2013 11:40 AM, Hiroshi Doyu wrote:
> Prashant Gaikwad <pgaikwad@...dia.com> wrote @ Wed, 6 Feb 2013 03:55:00 +0100:
>
>>>> No, clk_ops depends on the clocks you are using. There could be a clock
>>>> with mux and gate while another one with mux and div.
>>> You are right. What about the following? We don't have to have similar
>>> copy of clk_composite_ops for each instances.
>> Clock framework takes decision depending on the ops availability and it
>> does not know if the clock is mux or gate.
>>
>> For example,
>>
>>                   if (clk->ops->enable) {
>>                           ret = clk->ops->enable(clk->hw);
>>                           if (ret) {
>>                                   __clk_disable(clk->parent);
>>                                   return ret;
>>                           }
>>                   }
>>
>> in above case if clk_composite does not have gate clock then as per your
>> suggestion if it returns error value then it will fail and it is wrong.
> Ok, now I understand. Thank you for explanation.
>
> We always need to allocate clk_composite_ops for each clk_composite,
> right? If so what about having "struct clk_ops ops" in "struct
> clk_composite"?
>
> diff --git a/drivers/clk/clk-composite.c b/drivers/clk/clk-composite.c
> index f30fb4b..5240e24 100644
> --- a/drivers/clk/clk-composite.c
> +++ b/drivers/clk/clk-composite.c
> @@ -129,20 +129,13 @@ struct clk *clk_register_composite(struct device *dev, const char *name,
>                  pr_err("%s: could not allocate composite clk\n", __func__);
>                  return ERR_PTR(-ENOMEM);
>          }
> +       clk_composite_ops = &composite->ops;
>   
>          init.name = name;
>          init.flags = flags | CLK_IS_BASIC;
>          init.parent_names = parent_names;
>          init.num_parents = num_parents;
>   
> -       /* allocate the clock ops */
> -       clk_composite_ops = kzalloc(sizeof(*clk_composite_ops), GFP_KERNEL);
> -       if (!clk_composite_ops) {
> -               pr_err("%s: could not allocate clk ops\n", __func__);
> -               kfree(composite);
> -               return ERR_PTR(-ENOMEM);
> -       }
> -
>          if (mux_hw && mux_ops) {
>                  if (!mux_ops->get_parent || !mux_ops->set_parent) {
>                          clk = ERR_PTR(-EINVAL);
> @@ -202,7 +195,6 @@ struct clk *clk_register_composite(struct device *dev, const char *name,
>          return clk;
>   
>   err:
> -       kfree(clk_composite_ops);
>          kfree(composite);
>          return clk;
>   }
> diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h
> index f0ac818..bb5d36a 100644
> --- a/include/linux/clk-provider.h
> +++ b/include/linux/clk-provider.h
> @@ -346,6 +346,8 @@ struct clk_composite {
>          const struct clk_ops    *mux_ops;
>          const struct clk_ops    *div_ops;
>          const struct clk_ops    *gate_ops;
> +
> +       const struct clk_ops    ops;
>   };
>   
>   struct clk *clk_register_composite(struct device *dev, const char *name,

This will work, but there is no harm in allocating dynamically. What is 
preferred?

>
>>> diff --git a/drivers/clk/clk-composite.c b/drivers/clk/clk-composite.c
>>> index f30fb4b..8f88805 100644
>>> --- a/drivers/clk/clk-composite.c
>>> +++ b/drivers/clk/clk-composite.c
>>> @@ -27,6 +27,9 @@ static u8 clk_composite_get_parent(struct clk_hw *hw)
>>>           const struct clk_ops *mux_ops = composite->mux_ops;
>>>           struct clk_hw *mux_hw = composite->mux_hw;
>>>    
>>> +       if (!mux_hw->clk)
>>> +	       return -EINVAL;
>>> +
>>>           mux_hw->clk = hw->clk;
>> It is wrong.
> Will the above "mux_hw->clk = hw->clk" be removed from the original?

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