linux-kernel - Re: [RFC PATCH] i3c: dw: add option to disable runtime PM for DesignWare I3C controller

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Message-ID: <aPCg0bFm4-DnmhAp@shikoro>
Date: Thu, 16 Oct 2025 09:37:53 +0200
From: Wolfram Sang <wsa+renesas@...g-engineering.com>
To: Alexandre Belloni <alexandre.belloni@...tlin.com>
Cc: adrianhoyin.ng@...era.com, dinguyen@...nel.org, Frank.Li@....com,
	linux-i3c@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH] i3c: dw: add option to disable runtime PM for
 DesignWare I3C controller

> > Add a new Kconfig option, DW_I3C_DISABLE_RUNTIME_PM, that allows
> > disabling all runtime power management (PM) operations for the
> > Synopsys DesignWare I3C controller. When this option is selected,
> > the driver skips all runtime PM calls such as pm_runtime_enable(),
> > pm_runtime_get(), and pm_runtime_put(), keeping the controller
> > permanently active.
> 
> While the quirk may make sense, it definitively can't be activated by a
> Kconfig option. This should rather be tied to a new compatible string or
> a property.

I wondered why this is a quirk, at all, and not default behaviour. Is it
because it works with some RPM implementations and not with others,
depending on the platform?

But even if that is the case, it might be worth to opt-in for power
management instead of opting-out for buggy behaviour. Because I would
not assume that IBI have been thoroughly tested when a new platform
using this driver gets upstream. So, the buggy behaviour may only be
recognized later. Or?