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Fri, 13 Nov 2020 09:30:44 -0800 (PST) Date: Fri, 13 Nov 2020 18:30:42 +0100 From: Thierry Reding To: Dmitry Osipenko Cc: Mark Brown , Jonathan Hunter , Alan Stern , Peter Chen , Liam Girdwood , Adrian Hunter , Krzysztof Kozlowski , Greg Kroah-Hartman , Lee Jones , Uwe =?utf-8?Q?Kleine-K=C3=B6nig?= , Ulf Hansson , Mauro Carvalho Chehab , Rob Herring , Marek Szyprowski , Peter Geis , Nicolas Chauvet , linux-samsung-soc@vger.kernel.org, devel@driverdev.osuosl.org, linux-usb@vger.kernel.org, linux-pwm@vger.kernel.org, linux-mmc@vger.kernel.org, linux-kernel@vger.kernel.org, devicetree@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-media@vger.kernel.org, linux-tegra@vger.kernel.org Subject: Re: [PATCH v1 11/30] drm/tegra: dc: Support OPP and SoC core voltage scaling Message-ID: <20201113173042.GA1416567@ulmo> References: <20201111115534.GA4847@sirena.org.uk> <20201112171600.GD4742@sirena.org.uk> <20201112200123.GF4742@sirena.org.uk> <20201113142937.GB4828@sirena.org.uk> <7f066805-97d9-088f-e89d-a554fe478574@gmail.com> <20201113161550.GC4828@sirena.org.uk> <3beaa12b-4a50-a3b6-fc43-ebb5ce7a8db7@gmail.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="/04w6evG8XlLl3ft" Content-Disposition: inline In-Reply-To: <3beaa12b-4a50-a3b6-fc43-ebb5ce7a8db7@gmail.com> User-Agent: Mutt/1.14.7 (2020-08-29) Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org --/04w6evG8XlLl3ft Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Fri, Nov 13, 2020 at 08:13:49PM +0300, Dmitry Osipenko wrote: > 13.11.2020 19:15, Mark Brown =D0=BF=D0=B8=D1=88=D0=B5=D1=82: > > On Fri, Nov 13, 2020 at 06:55:27PM +0300, Dmitry Osipenko wrote: > >> 13.11.2020 17:29, Mark Brown =D0=BF=D0=B8=D1=88=D0=B5=D1=82: > >=20 > >>> It's not clear if it matters - it's more a policy decision on the part > >>> of the driver about what it thinks safe error handling is. If it's n= ot > >=20 > >> If regulator_get() returns a dummy regulator, then this means that > >> regulator isn't specified in a device-tree. But then the only way for a > >> consumer driver to check whether regulator is dummy, is to check > >> presence of the supply property in a device-tree. > >=20 > > My point here is that the driver shouldn't be checking for a dummy > > regulator, the driver should be checking the features that are provided > > to it by the regulator and handling those. >=20 > I understand yours point, but then we need dummy regulator to provide > all the features, and currently it does the opposite. But that's exactly Mark's point. Any regular regulator could be lacking all of the features just as well. If the regulator supports a fixed voltage, then it's not going to allow you to set a different one, etc. The point is that the regulator consumer should then be written in a way to deal with varying levels of features. 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