linux-kernel - Re: [PATCH] clk: prevent erronous parsing of children during rate change

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Message-ID: <5424C2FA.4000508@codeaurora.org>
Date:	Thu, 25 Sep 2014 18:35:54 -0700
From:	Stephen Boyd <sboyd@...eaurora.org>
To:	Tero Kristo <t-kristo@...com>
CC:	linux-kernel@...r.kernel.org, linux-omap@...r.kernel.org,
	tony@...mide.com, nm@...com, mturquette@...aro.org,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] clk: prevent erronous parsing of children during rate
 change

On 09/23/14 06:38, Tero Kristo wrote:
> On 09/22/2014 10:18 PM, Stephen Boyd wrote:
>> On 08/21, Tero Kristo wrote:
>>>           /* Skip children who will be reparented to another clock */
>>>           if (child->new_parent && child->new_parent != clk)
>>>               continue;
>>
>> Are we not hitting the new_parent check here? I don't understand
>> how we can be changing parents here unless the check is being
>> avoided, in which case I wonder why determine_rate isn't being
>> used.
>>
>
> It depends how the clock underneath handles the situation. The error I
> am seeing actually happens with a SoC specific compound clock (DPLL)
> which integrates set_rate + mux functionality into a single clock
> node. A call to the clk_set_rate changes the parent of this clock
> (from bypass clock to reference clock), in addition to changing the
> rate (tune the mul+div.) I looked at using the determine rate call
> with this type but it breaks everything up... the parent gets changed
> but not the clock rate, in addition to some other issues.

Ok. Is this omap3_noncore_dpll_set_rate()? Can we use determine_rate +
clk_set_parent_and_rate()? At least clk_set_parent_and_rate() would
allow us to do the mult+div and the parent in the same op call, although
I don't understand why setting the parent and then setting the rate is
not going to work. I'm interested in the other issues that you mentioned
too.

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