linux-kernel - Re: [PATCH v3 3/3] arm: omap_hwmod disable ick autoidling when a hwmod requires that

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Date:   Mon, 21 Jan 2019 09:12:41 +0200
From:   Tero Kristo <t-kristo@...com>
To:     Tony Lindgren <tony@...mide.com>,
        Andreas Kemnade <andreas@...nade.info>
CC:     <mturquette@...libre.com>, <sboyd@...nel.org>,
        <linux-omap@...r.kernel.org>, <linux-clk@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <bcousson@...libre.com>,
        <paul@...an.com>, <letux-kernel@...nphoenux.org>
Subject: Re: [PATCH v3 3/3] arm: omap_hwmod disable ick autoidling when a
 hwmod requires that

On 18/01/2019 21:45, Tony Lindgren wrote:
> * Andreas Kemnade <andreas@...nade.info> [190118 19:39]:
>> Hi,
>>
>> On Fri, 18 Jan 2019 10:36:30 -0800
>> Tony Lindgren <tony@...mide.com> wrote:
>>
>> [...]
>>> til the next workaround.
>>>
>>>> That flags also causes the iclk being enabled/disabled
>>>> manually.
>>>
>>> Yes but SWSUP_IDLE for the interface clock to me currently
>>> just means:
>>>
>>> "manually enable and disable ocp interface clock"
>>>
>> well, if we want to manually disable it and not automatically,
>> we have to disable autoidle or it will be automatically disabled.
>>
>> Disabling it manually when it is already auto-disabled (by autoidle) is
>> just practically a no-op towards the clock.
> 
> OK I buy that :) It should be probably added to the patch
> description to make it clear what it changes.
> 
> Tero, any comments on this change?

Well, seeing the flag is pretty much only used for a handful of hwmods 
nowadays, it should be fine. OMAP3 PM should be tested with this change 
though, as there are couple of hwmods impacted on that platform. I 
wonder what happens to cpuidle when display is active...

-Tero

> 
>>> and with your changes it becomes:
>>>
>>> "manually enable and disable ocp interface clock and block
>>>   autoidle while in use".
>>>
>>> So aren't we now changing the way things behave in general
>>> for SWSUP_IDLE?
>>>
>> Yes, we are, so proper testing is needed. But If I read those comments
>> it was always intended this way but not fully implemented because it
>> appeared to be more work like needing a usecounter (which my patchset
>> also adds) for that autoidle flag.
> 
> OK yeah the use count seems necessary. I'll test here
> with my PM use cases.
> 
> Regards,
> 
> Tony
> 

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