linux-kernel - Re: [RFC PATCH 0/2] Propose critical clocks

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Date:   Thu, 6 Oct 2022 13:05:08 +0200
From:   Marek Vasut <marex@...x.de>
To:     Stephen Boyd <sboyd@...nel.org>,
        Marco Felsch <m.felsch@...gutronix.de>, abel.vesa@...aro.org,
        abelvesa@...nel.org, festevam@...il.com, kernel@...gutronix.de,
        krzysztof.kozlowski+dt@...aro.org, mturquette@...libre.com,
        robh+dt@...nel.org, s.hauer@...gutronix.de, shawnguo@...nel.org
Cc:     Peng Fan <peng.fan@....com>, linux-clk@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-imx@....com
Subject: Re: [RFC PATCH 0/2] Propose critical clocks

On 10/6/22 01:06, Stephen Boyd wrote:
> Quoting Marco Felsch (2022-10-05 01:23:48)
>> Hi Stephen, Michael,
>>
>> I know it is a busy time right now, but maybe you have a few minutes for
>> this RFC. I know it is incomplete, but the interessting part is there
>> and it would fix a real issue we encountered on the imx8mm-evk's.

The i.MX8M hang when using 32kHz supplied by PMIC is solved by modeling 
the clock in DT correctly, see:

https://lore.kernel.org/all/20220924174603.458956-1-marex@denx.de/

> There's another approach by Marek[1]. Can you work together on a
> solution? I think we should step away from trying to make the critical
> flag work during clk registration, and turn on the clk during provider
> registration instead.

So that would work like the qualcomm-specific 'protected-clock' property?

I really want to avoid such clock-driver specific hacks which are poorly 
or inconsistently supported. This critical-clock should be a generic 
solution and that should be in clock core.

> That hopefully makes it simpler. We can keep the
> clk flag of course, so that the clk can't be turned off, but otherwise
> we shouldn't need to make registration path check for the property.
> 
> [1] https://lore.kernel.org/all/20220924174517.458657-1-marex@denx.de/