From mboxrd@z Thu Jan 1 00:00:00 1970 From: Maxime Ripard Subject: Re: [PATCH 13/20] drm/bridge: Add RGB to VGA bridge support Date: Thu, 26 May 2016 11:38:12 +0200 Message-ID: <20160526093812.GN9232@lukather> References: <1463402840-17062-1-git-send-email-maxime.ripard@free-electrons.com> <1463402840-17062-14-git-send-email-maxime.ripard@free-electrons.com> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="b1ERR0FXR0PvNIRE" Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-clk-owner@vger.kernel.org To: Rob Herring Cc: Chen-Yu Tsai , Mike Turquette , Stephen Boyd , Daniel Vetter , David Airlie , Boris Brezillon , Laurent Pinchart , dri-devel , "linux-arm-kernel@lists.infradead.org" , "devicetree@vger.kernel.org" , linux-clk List-Id: devicetree@vger.kernel.org --b1ERR0FXR0PvNIRE Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Hi Rob, On Mon, May 16, 2016 at 09:07:18AM -0500, Rob Herring wrote: > On Mon, May 16, 2016 at 7:47 AM, Maxime Ripard > wrote: > > Some boards have an entirely passive RGB to VGA bridge, based on either > > DACs or resistor ladders. > > > > Those might or might not have an i2c bus routed to the VGA connector in > > order to access the screen EDIDs. > > > > Add a bridge that doesn't do anything but expose the modes available on= the > > screen, either based on the EDIDs if available, or based on the XGA > > standards. > > > > Signed-off-by: Maxime Ripard > > --- > > .../bindings/display/bridge/dumb-vga.txt | 40 +++++ > > drivers/gpu/drm/bridge/Kconfig | 6 + > > drivers/gpu/drm/bridge/Makefile | 1 + > > drivers/gpu/drm/bridge/dumb-vga.c | 186 +++++++++++++= ++++++++ > > 4 files changed, 233 insertions(+) > > create mode 100644 Documentation/devicetree/bindings/display/bridge/du= mb-vga.txt > > create mode 100644 drivers/gpu/drm/bridge/dumb-vga.c > > > > diff --git a/Documentation/devicetree/bindings/display/bridge/dumb-vga.= txt b/Documentation/devicetree/bindings/display/bridge/dumb-vga.txt > > new file mode 100644 > > index 000000000000..757f04de97f3 > > --- /dev/null > > +++ b/Documentation/devicetree/bindings/display/bridge/dumb-vga.txt > > @@ -0,0 +1,40 @@ > > +Passive RGB to VGA bridge > > +------------------------- > > + > > +This binding is aimed for entirely passive RGB to VGA bridges that do = not > > +require any configuration. >=20 > No reset or enable lines or regulators? On the three designs I've seen: - One doesn't need any of these - One has a GPIO enable pin but with it's resistor not populated - One has a regulator controlled by a GPIO So I guess in most cases, we don't need anything, but we still might to cover all cases. > > + > > +Required properties: > > + > > +- compatible: Should be "dumb-vga-bridge" > > + > > +Optional properties: > > + > > +- ddc-i2c-bus: phandle to the i2c bus used to communicate with the mon= itor >=20 > The i2c bus is a property of the connector, not the bridge chip, so it > belongs in a VGA connector node (which we already have binding for). >=20 > I think for the really "dumb" (or transparent case), you should only > have a connector. For anything more complex, then you should have both > a DAC and connector node. So, in essence, something like: https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/arch/a= rm/boot/dts/r8a7794-alt.dts#n37 =20 > On the driver side, I think we could handle multiple connectors with a > single driver. Ideally, that would work with any DRM driver that has a > connector node. I'm not sure what you mean by that. I really think it should be a separate driver in order to share the common code that so far the current implementations put in some driver specific code (even though it might be completely generic). Thanks! Maxime --=20 Maxime Ripard, Free Electrons Embedded Linux, Kernel and Android engineering http://free-electrons.com --b1ERR0FXR0PvNIRE Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iQIcBAEBAgAGBQJXRsQDAAoJEBx+YmzsjxAgkQAQAMMiUvyTRegGjb8uDeCtNdp/ 6iArK2He6Kk6VKhw0kNb1V0mJVZnry/Ve4lcXhzzrADeWhXy+W9YgxUsRCzH0SR1 fkMue0IjXI7I2UwR0zGnNHl0mxFf1zsHCXtDidMaXpu/BI5oFePwpzxOct/913iG a1ZL0DgAJorTrPhg2fqjwcbrQm7dXtaZDerw0v+pmnixmCTryo24W8LY8tbZFAEj lhAftFisZxHV4o6tEKIPmjkE9NS+BHUXYNU2Otpq9jySPODT2m9bWRIUGUSddJop 1UN79/8ygNw1wP+jE+qzeUcgTwJlgT4hSu3hD4Mb4zPD31bPiO2WA7xZtj2RtC1r UZu1cpLIFAHhMtO5GdVOMcR8gs+P/044kIQa1/4/Z1qltt95IwpLZ88jdqi0dsnJ PoIkO1HN8ktnWr0CW4gltdYJO4h+SkTTDglDQPj+EVnvRM2nUS12MMx9xx5m86d1 u4XXigk78n1d5Geu1MBFBsR1qcD6kr9DHTKTQ1mxigb0pomufJXqWLJWcjE8c/sq 8ph/CTK1jvvEa383u0XDUrIrZbgXAwn9VsckKlFnSp5Fq9D4ZCsy/hVVOFUuTSmk dWCH/gO/g0LJgN9a8GeNnubnLKBmRTi3cBon/ZIFgKJ06GM2JlNdyDxJIXNy5jhQ FG7hZLnO6+hf5LioTalJ =PIIh -----END PGP SIGNATURE----- --b1ERR0FXR0PvNIRE--