linux-kernel - RE: [PATCH RFC 1/2] regmap: add option to disable debugfs

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Date:   Mon, 20 Jun 2022 15:47:05 +0000
From:   Aisheng Dong <aisheng.dong@....com>
To:     Mark Brown <broonie@...nel.org>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "dongas86@...il.com" <dongas86@...il.com>,
        "l.stach@...gutronix.de" <l.stach@...gutronix.de>,
        Peng Fan <peng.fan@....com>,
        "shawnguo@...nel.org" <shawnguo@...nel.org>
Subject: RE: [PATCH RFC 1/2] regmap: add option to disable debugfs

> From: Mark Brown <broonie@...nel.org>
> Sent: Monday, June 20, 2022 11:06 PM
> 
> On Mon, Jun 20, 2022 at 09:47:57PM +0800, Dong Aisheng wrote:
> > The regmap core will create debugfs by default for each instance.
> > However, it's fairly possible that some devices may not work properly
> > with regmap registers dump via debugfs due to it may be in suspend
> > state (e.g. Power domain is off).
> >
> > Current regmap core does not support runtime pm for MMIO bus.
> > Although there have been several retries [1] in community but finally
> > didn't get accepted.
> >
> > This patch adds an option to allow drivers to claim no debugfs support
> > due to possible platform limitations.
> >
> > 1. Link: https://lkml.iu.edu/hypermail/linux/kernel/1204.0/01646.html
> 
> As indicated in the message you're linking to here if the device can't be
> accessed it should be being put in cache only mode which will ensure that
> nothing can do any physical accesses.

I wonder that's not a stable solution assuming there're possible volatile registers.
Isn't that?

Regards
Aisheng