linux-kernel - Re: [PATCH 1/4] clk: propagate parent change up one level

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Message-ID: <536176DD.5020507@gmail.com>
Date:	Thu, 01 May 2014 00:19:09 +0200
From:	Tomasz Figa <tomasz.figa@...il.com>
To:	Tomasz Figa <t.figa@...sung.com>,
	Tomasz Stanislawski <t.stanislaws@...sung.com>,
	linux-kernel@...r.kernel.org, linux-samsung-soc@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org,
	dri-devel@...ts.freedesktop.org, mturquette@...aro.org
CC:	kgene.kim@...sung.com, sw0312.kim@...sung.com,
	rob.herring@...xeda.com, kishon@...com, a.hajda@...sung.com,
	kyungmin.park@...sung.com, sylvester.nawrocki@...il.com
Subject: Re: [PATCH 1/4] clk: propagate parent change up one level

Mike,

On 08.04.2014 17:45, Tomasz Figa wrote:
> Hi,
>
> On 04.04.2014 16:53, Tomasz Stanislawski wrote:
>> This patch adds support for propagation of setup of clock's parent one
>> level
>> up.
>>
>> This feature is helpful when a driver changes topology of its clocks
>> using
>> clk_set_parent().  The problem occurs when on one platform/SoC
>> driver's clock
>> is located at MUX output but on the other platform/SoC there is a
>> gated proxy
>> clock between the MUX and driver's clock.  In such a case, driver's
>> code has to
>> be modified to use one clock for enabling and the other clock for
>> setup of a
>> parent.
>>
>> The code updates are avoided by propagating setup of a parent up one
>> level.
>>
>> Additionally, this patch adds CLK_SET_PARENT_PARENT (sorry for naming)
>> flag to
>> inform clk-core that clk_set_parent() should be propagated.
>>
>> Signed-off-by: Tomasz Stanislawski <t.stanislaws@...sung.com>
>> ---
>>   drivers/clk/clk.c            |    6 ++++++
>>   include/linux/clk-provider.h |    1 +
>>   2 files changed, 7 insertions(+)
>>
>> diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
>> index dff0373..53bbfda 100644
>> --- a/drivers/clk/clk.c
>> +++ b/drivers/clk/clk.c
>> @@ -1737,6 +1737,12 @@ int clk_set_parent(struct clk *clk, struct clk
>> *parent)
>>
>>       /* try finding the new parent index */
>>       if (parent) {
>> +        if ((clk->flags & CLK_SET_PARENT_PARENT)
>> +            && clk->num_parents == 1) {
>> +            ret = clk_set_parent(clk->parent, parent);
>> +            goto out;
>> +        }
>> +
>>           p_index = clk_fetch_parent_index(clk, parent);
>>           p_rate = parent->rate;
>>           if (p_index < 0) {
>> diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h
>> index 5119174..daa0b03 100644
>> --- a/include/linux/clk-provider.h
>> +++ b/include/linux/clk-provider.h
>> @@ -30,6 +30,7 @@
>>   #define CLK_GET_RATE_NOCACHE    BIT(6) /* do not use the cached clk
>> rate */
>>   #define CLK_SET_RATE_NO_REPARENT BIT(7) /* don't re-parent on rate
>> change */
>>   #define CLK_GET_ACCURACY_NOCACHE BIT(8) /* do not use the cached clk
>> accuracy */
>> +#define CLK_SET_PARENT_PARENT    BIT(9) /* propagate parent change up
>> one level */
>>
>>   struct clk_hw;
>>   struct dentry;
>>
>
> This would be very useful, at least on Exynos platforms, with
> mux-div-gate clock paths. PARENT_PARENT sounds a bit funny, though.
>
> Reviewed-by: Tomasz Figa <t.figa@...sung.com>

Your opinion on this would be greatly appreciated.

Best regards,
Tomasz

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