linux-kernel - Re: [PATCH 1/1] regmap: debugfs: runtime resume a device when reading registers

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Message-ID: <6c4d37c1-9376-46b7-bd75-e68b84adbbd5@sirena.org.uk>
Date: Wed, 10 Jan 2024 13:04:39 +0000
From: Mark Brown <broonie@...nel.org>
To: Alexander Stein <alexander.stein@...tq-group.com>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"Rafael J . Wysocki" <rafael@...nel.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] regmap: debugfs: runtime resume a device when
 reading registers

On Wed, Jan 10, 2024 at 01:46:31PM +0100, Alexander Stein wrote:
> Am Mittwoch, 10. Januar 2024, 13:23:17 CET schrieb Mark Brown:

> > The idea is that the debugfs interface isn't supposed to be disruptive
> > to the thing being debugged.  It would be better to detect if there will
> > be problems and report the status as busy.

> In my case the device is actually unused, runtime suspended, thus disabled 
> power domain. That's totally different to busy. In this case dumping the 
> registers is non-disruptive, unless you account enabling/disabling the power 
> domain as well. Any attached clock is already enabled/disabled, but power 
> domains are not.

At a regmap level we map that onto -EBUSY for devices with a cache
(using a cache for your specific device ought to DTRT, it's not a
general solution though).

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