Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Fri, 4 Feb 2022 19:41:01 +0000
From:   Mark Brown <broonie@kernel.org>
To:     Brian Norris <briannorris@chromium.org>
Cc:     Peng Fan <peng.fan@nxp.com>,
        "rafael@kernel.org" <rafael@kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        dl-linux-imx <linux-imx@nxp.com>,
        "S.j. Wang" <shengjiu.wang@nxp.com>
Subject: Re: regmap: mmio: lack of runtime_pm support for debugfs
Message-ID: <Yf2BTelNlqplv06/@sirena.org.uk>
References: <1587620791-5279-1-git-send-email-peng.fan@nxp.com>
 <20200423104000.GD4808@sirena.org.uk>
 <DB6PR0402MB27600084E4A040609EF620A088D30@DB6PR0402MB2760.eurprd04.prod.outlook.com>
 <20200423112244.GH4808@sirena.org.uk>
 <DB6PR0402MB2760FBCA05C1BADB27F0356488D00@DB6PR0402MB2760.eurprd04.prod.outlook.com>
 <20200424103004.GB5850@sirena.org.uk>
 <Ye87P19+JOjPEGTY@google.com>
 <Yf14RJbM10O3RdA+@sirena.org.uk>
 <CA+ASDXP+KeiRKASFakDjJ=cZPD_rGmV4=JgRH26zQi-uZDdiAQ@mail.gmail.com>
MIME-Version: 1.0
Content-Type: multipart/signed; micalg=pgp-sha512;
        protocol="application/pgp-signature"; boundary="+iMZOw02us7dat7E"
Content-Disposition: inline
In-Reply-To: <CA+ASDXP+KeiRKASFakDjJ=cZPD_rGmV4=JgRH26zQi-uZDdiAQ@mail.gmail.com>
Precedence: bulk


--+iMZOw02us7dat7E
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline

On Fri, Feb 04, 2022 at 11:21:51AM -0800, Brian Norris wrote:
> On Fri, Feb 4, 2022 at 11:02 AM Mark Brown <broonie@kernel.org> wrote:

> > Are you sure you wouldn't be better off with a cache here, or marking
> > the registers as precious so they don't get read (perhaps conditionally
> > to allow reading while the device is live)?

> We do actually have a cache for the case I care about, but there's
> also a debugfs file for bypassing that and...for some reason I'm
> dealing with some diagnostic scripts that purposely toggle that. I'm
> not sure how wise that is, but in general I like to reduce the number
> of ways dumb user space can screw things up. I've even had to tell
> people that recursively grepping through sysfs or debugfs is a bad
> idea...

Are you sure this extra thing that bypasses the cache isn't an out of
tree patch?  It really doesn't sound like a good idea to have that, and
if people think they need it they probably have drivers doing something
quite unfortunate.  Or are you just looking at the upstream debugfs with
some volatile registers?

--+iMZOw02us7dat7E
Content-Type: application/pgp-signature; name="signature.asc"

-----BEGIN PGP SIGNATURE-----

iQEzBAABCgAdFiEEreZoqmdXGLWf4p/qJNaLcl1Uh9AFAmH9gUwACgkQJNaLcl1U
h9B6QQf/V8FpQD0c3GxBAmnKaiJB8IF+/cyPMz72rvNFzk4ZoFdsu2ByVfL+Zrj9
EZEOpisWGmEfzH/L8+pnBKYJu7JqoZWmTItTl2uTX1MBexqrXUko7XnKhYn0GeC1
ADBkssPDFNVGJIKZ8fB00Zx4vWkTUBtvgIxHGWfTPRlZyCsCv2Uq+4zefavk3WoJ
swRa63Syj1MG0kAEU865WcMoCddNmmrEz4eQYv9zwRkOIY+JPB3bUzYrHcNV+USV
jhRYn2Jdz4i+NHCASAGOB0PBvNrFlvDbA6r3mQPhG5r4gMpF6ki5PiQj6YyZ+mbj
bm3bSj5cEpQra7AA79Kz8+XzE3NxUg==
=cp59
-----END PGP SIGNATURE-----

--+iMZOw02us7dat7E--