From mboxrd@z Thu Jan 1 00:00:00 1970 From: Thierry Reding Subject: Re: [PATCH v4 00/11] drm: add support for Atmel HLCDC Display Controller Date: Thu, 21 Aug 2014 15:16:08 +0200 Message-ID: <20140821131552.GA19293@ulmo.nvidia.com> References: <1406034695-15534-1-git-send-email-boris.brezillon@free-electrons.com> <20140821081619.GZ2452@ldesroches-Latitude-E6320> <20140821103706.2349915d@bbrezillon> <20140821090406.GA13733@ulmo> <20140821114159.319e741b@bbrezillon> <20140821095202.GA21848@ulmo> <20140821150600.37788d82@bbrezillon> Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="===============0917392802==" Return-path: In-Reply-To: <20140821150600.37788d82@bbrezillon> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" To: Boris BREZILLON Cc: Mark Rutland , linux-pwm@vger.kernel.org, Samuel Ortiz , Pawel Moll , devicetree@vger.kernel.org, Lee Jones , Ian Campbell , Nicolas Ferre , linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, Rob Herring , Ludovic Desroches , Alexandre Belloni , Laurent Pinchart , Bo Shen , Kumar Gala , Jean-Christophe Plagniol-Villard , Andrew Victor , linux-arm-kernel@lists.infradead.org List-Id: devicetree@vger.kernel.org --===============0917392802== Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="gKMricLos+KVdGMg" Content-Disposition: inline --gKMricLos+KVdGMg Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Thu, Aug 21, 2014 at 03:06:00PM +0200, Boris BREZILLON wrote: > On Thu, 21 Aug 2014 11:52:03 +0200 > Thierry Reding wrote: >=20 > > On Thu, Aug 21, 2014 at 11:41:59AM +0200, Boris BREZILLON wrote: > > > On Thu, 21 Aug 2014 11:04:07 +0200 > > > Thierry Reding wrote: > > >=20 > > > > On Thu, Aug 21, 2014 at 10:37:06AM +0200, Boris BREZILLON wrote: > > > > > Hi Ludovic, > > > > >=20 > > > > > On Thu, 21 Aug 2014 10:16:19 +0200 > > > > > Ludovic Desroches wrote: > > > > >=20 > > > > > > Hi Boris, > > > > > >=20 > > > > > > You can add > > > > > >=20 > > > > > > Tested-by: Ludovic Desroches > > > > >=20 > > > > > Thanks for testing this driver. > > > > >=20 > > > > > >=20 > > > > > > Only one issue but not related to your patches, you can't displ= ay > > > > > > quickly the bootup logo since the panel detection takes too much > > > > > > time. > > > > >=20 > > > > > Yes, actually this is related to the device probe order: the > > > > > hlcdc-display-controller device is probed before the simple-panel= , thus > > > > > nothing is detected on the RGB connector (I use of_drm_find_panel= to > > > > > check for panel availability) when the display controller is > > > > > instantiated. I rely on the default polling infrastructure provid= ed by > > > > > the DRM/KMS framework which polls for a new connector every 10s, = and > > > > > this is far more than you kernel boot time. > > > > >=20 > > > > > Do anyone see a solution to reduce this delay (without changing t= he > > > > > polling interval). I thought we could add a notifier infrastructu= re to > > > > > the DRM panel framework, but I'm not sure this is how you want th= ings > > > > > done... > > > >=20 > > > > Other drivers return -EPROBE_DEFER when a panel hasn't been registe= red > > > > yet. This will automatically take care of ordering things in a way = that > > > > DRM/KMS will only be initialized after the panel has been probed. > > >=20 > > > Actually I'd like to avoid doing this with a deferred probe, because, > > > AFAIU, the remote endpoint is not tightly linked with the display > > > controller driver (I mean the display controller can still be > > > initialized without having a display connected on it). > > > Moreover the atmel dev kit I'm using has an HDMI bridge connected on > > > the same RGB connector and I'd like to use it in a near future. > > > Returning -EPROBE_DEFER in case of several devices connected on the > > > same connector implies that I'll have to wait for all the remote > > > end-points to be available before my display controller could be > > > instantiated. > > >=20 > > > While this could be acceptable when all drivers are statically linked > > > in the kernel, it might be problematic when you're using modules, > > > meaning that you won't be able to display anything on your LCD panel > > > until your HDMI bridge module has been loaded. > >=20 > > No. HDMI should be using proper hotplugging anyway, hence it should be > > always be loaded anyway. You're in for a world of pain if you think you > > can run DRM with a driver that's composed of separate kernel modules. >=20 > I was talking about the external RGB to HDMI encoder, should the driver > for this encoder (which is not on On Chip block) be compiled > statically too ? >=20 > >=20 > > Also if you don't want to use deferred probe, then you're in for the > > full hotplugging panel dance and that implies that you need to fix a > > bunch of things in DRM (one being the framebuffer console instantiation > > that I referred to in the other thread). >=20 > For now, I wait until there is a device connected on the RGB connector > (connector status set to connector_status_connected) before creating an > fbdev. It might not be the cleanest way to solve this issue, but it > works :-). Yeah, I guess that's one way to do it. But it's tricky to get right when you have several outputs. Which one should be considered the primary and trigger fbdev creation? > > You also can't be using the > > current device tree bindings because they all assume a dependency from > > the display controller/output to the panel. For hotplugging you'd need > > the dependency the other way around (the panel needs to refer to the > > output by phandle). >=20 > Here [1] is a proposal for notification support in the drm_panel > infrastructure (which is not that complicated), and here [2] is how > I use it in my atmel-hlcdc driver to generate hotplug events. >=20 > Let me know if you want me to submit a proper patch series... >=20 > Best Regards, >=20 > Boris >=20 > [1]http://code.bulix.org/scq4g3-86804 > [2]http://code.bulix.org/7dg501-86805 Those look interesting. Any chance you could look into how to do the same without resorting to notifiers? Thierry --gKMricLos+KVdGMg Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v2 iQIcBAEBAgAGBQJT9fEIAAoJEN0jrNd/PrOhgGoP/0VcZa+s3shZQ1wXu8H2Kf2u UoBRVTeRNypZ2e0HsMbNOv+qZsQDZ23DIOhcGtMnbSZWc84tTPkuCDk5MhO1RTn5 d0d+4b6JEVNLvLXY6emif9YbGd6un+SC6ZJ8bpkVKuEihD3q7qalNi2bt/j9ZdAB sQSOR1QGfnfZ2hOlHhl83C5WXIEB5sMpNHHWfrCss9MgJcvhhIC+tZzio+0FRFs/ 7Czl3qdvSG5AKNWmFQNg0dD2Qf16xYlxpSbmcF+W/yaM4O6pTJSbgbiemeBuMrVS O+fL79BRwxMmwpXK4YDHC2sWxjlRtmsdzOjjm6rAmSjWsbNOxMW0dbOULDVj5ZkA 7BtfDzpHNAPS2sZYbyq0rdEagfwEtYXj/Ey9n/cjYmt+QEhoYTLG2AAraFEC28N3 KPOSsSF3J5zEOisFMkJRLfX7acOmRBpMIX2cVSBolX9tH+CkRij5aTJKYk5J40aa XkilcaMDlLgOx6+fznLG4oD0XgVbTJWOXrkkvok2FEiiEjbeCX9w1PVtkqMuNFvx +LgEhVs+ryKl+75k1SOE5RgUjwUmVVuEpA54/1HECsZL2IEAJmxbbhKXhVyIzByZ auK17GNQ+39ANKWEyUnOubat59kCYP8LsJ8oE1uVb2DfOiREzhwVNg8iFOfnG0uP TPsssKQWh8LreW88d0ZD =E0mK -----END PGP SIGNATURE----- --gKMricLos+KVdGMg-- --===============0917392802== Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline _______________________________________________ dri-devel mailing list dri-devel@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/dri-devel --===============0917392802==--