linux-kernel - Re: [RESEND 2/2] clk: Add driver for Palmas clk32kg and clk32kgaudio clocks

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Date:	Mon, 30 Jun 2014 08:56:55 +0300
From:	Peter Ujfalusi <peter.ujfalusi@...com>
To:	Javier Martinez Canillas <javier@...hile0.org>
CC:	Mike Turquette <mturquette@...aro.org>,
	Grant Likely <grant.likely@...aro.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	"linux-omap@...r.kernel.org" <linux-omap@...r.kernel.org>,
	<ldewangan@...dia.com>, <linux-doc@...r.kernel.org>,
	Nishanth Menon <nm@...com>, Rob Herring <robh+dt@...nel.org>
Subject: Re: [RESEND 2/2] clk: Add driver for Palmas clk32kg and clk32kgaudio
 clocks

Hi Javier,

On 06/27/2014 09:23 PM, Javier Martinez Canillas wrote:
> Hello Peter,
> 
> On Fri, Jun 27, 2014 at 8:01 AM, Peter Ujfalusi <peter.ujfalusi@...com> wrote:
>> Palmas class of devices can provide 32K clock(s) to be used by other devices
>> on the board. Depending on the actual device the provided clocks can be:
>> CLK32K_KG and CLK32K_KGAUDIO
>> or only one:
>> CLK32K_KG (TPS659039 for example)
>>
>> Use separate compatible flags for the two 32K clock.
>> A system which needs or have only one of the 32k clock from
>> Palmas will need to add node(s) for each clock as separate section
>> in the dts file.
>> The two compatible property is:
>> "ti,palmas-clk32kg" for clk32kg clock
>> "ti,palmas-clk32kgaudio" for clk32kgaudio clock
>>
>> Apart from the register control of the clocks - which is done via
>> the clock API there is a posibility to enable the external sleep
>> control. In this way the clock can be enabled/disabled on demand by the
>> user of the clock.
>>
>> See the documentation for more details.
>>
>> Signed-off-by: Peter Ujfalusi <peter.ujfalusi@...com>
>> Reviewed-by: Nishanth Menon <nm@...com>

>> +static unsigned long palmas_clks_recalc_rate(struct clk_hw *hw,
>> +                                            unsigned long parent_rate)
>> +{
>> +       return 32768;
>> +}
> 
> I see that other clock drivers using a constant rate return 0 if the
> clock has not been enabled.

and there are examples when similar fixed clock drivers returns only the clock
value, like clk-max77686. I can not find clear guidelines neither in the
documentation or around the header/c files for this.
Mike, what is the appropriate way of handling the recalc_rate?

> So maybe is more correct to have something
> like the following?
> 
> if (__clk_is_enabled(hw->clk))
>         return 32768;
> else
>         return 0;
> 
> Best regards,
> Javier
> 


-- 
Péter
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