linux-kernel - Re: [PATCH 0/2] clk: renesas: rzg2l: Disable unused clocks after resume

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Message-ID: <785d826f-232c-482f-a54c-e6baad39f502@tuxon.dev>
Date: Sat, 30 Aug 2025 14:29:16 +0300
From: Claudiu Beznea <claudiu.beznea@...on.dev>
To: Brian Masney <bmasney@...hat.com>, Stephen Boyd <sboyd@...eaurora.org>
Cc: mturquette@...libre.com, sboyd@...nel.org, geert+renesas@...der.be,
 linux@...linux.org.uk, linux-renesas-soc@...r.kernel.org,
 linux-arm-kernel@...ts.infradead.org, linux-clk@...r.kernel.org,
 linux-kernel@...r.kernel.org,
 Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
Subject: Re: [PATCH 0/2] clk: renesas: rzg2l: Disable unused clocks after
 resume

Hi, Stephen,

On 26.08.2025 14:52, Brian Masney wrote:
> Hi Claudiu,
> 
> On Tue, Aug 26, 2025 at 02:01:56PM +0300, claudiu beznea wrote:
>> On 8/25/25 20:05, Brian Masney wrote:
>>> On Thu, Aug 21, 2025 at 11:03:30AM +0300, Claudiu wrote:
>>>> From: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
>>>> This series disables clocks that remain unused after resume.
>>>> This is necessary when the resume process is done with the help of the
>>>> bootloader, as the bootloader enables various clocks when returning from
>>>> resume.
>>>>
>>>> On the RZ/G3S SoC (where this series was tested), the bootloader enables
>>>> the SDHI clocks (for all SDHI modules, of which 2 are used by Linux and
>>>> 1 is unused) and the clocks for a serial IP (unused by Linux).
>>>>
>>>> Testing was done on the RZ/G3S SMARC Carrier II board.
>>>
>>> Do you think that other boards would also benefit from this change? If
>>> so, what do you think about putting the call to register_pm_notifier()
>>> inside an __init block in clk.c so that this same change doesn't have to
>>> be implemented across various clk drivers?
>>
>> Yes, that was my other approach I was thinking about. I wanted to see how
>> other people consider this version.
>>
>>>
>>> Alternatively, if this is board specific, could this be fixed in the
>>> boot loader so that the clock that's not used by Linus is properly shut
>>> down on resume?
>>
>> As a result of your request I did some more investigations on my side, I can
>> say that, yes, in theory that could be also handled by bootloader.
>>
>> I can drop this and try to do it in bootloader, if any. Please let me know
>> if you still consider this (or the variant that implements it in a generic
>> way) necessary.
> 
> Personally I would go the route of fixing this in the bootloader for
> this particular platform.
> 
> If this issue affects other platforms, particularly across multiple
> SoC vendors, then I think it would be worthwhile to have a discussion
> about adding this functionality to the clk core.
> 

Could you please let us know if you prefer a mechanism like
clk_disable_unused() in Linux for resume path?

Thank you,
Claudiu