From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756460Ab3IDWYc (ORCPT ); Wed, 4 Sep 2013 18:24:32 -0400 Received: from avon.wwwdotorg.org ([70.85.31.133]:38519 "EHLO avon.wwwdotorg.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753309Ab3IDWYa (ORCPT ); Wed, 4 Sep 2013 18:24:30 -0400 Message-ID: <5227B31A.3070404@wwwdotorg.org> Date: Wed, 04 Sep 2013 16:24:26 -0600 From: Stephen Warren User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130803 Thunderbird/17.0.8 MIME-Version: 1.0 To: Mikko Perttunen CC: Mikko Perttunen , thierry.reding@gmail.com, tbergstrom@nvidia.com, dri-devel@lists.freedesktop.org, linux-tegra@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 3/6] host1x: hdmi: Enable Vdd earlier for hotplug/DDC References: <1377704922-2824-1-git-send-email-mperttunen@nvidia.com> <1377704922-2824-4-git-send-email-mperttunen@nvidia.com> <52277F90.40109@wwwdotorg.org> <5227AE4F.8050603@kapsi.fi> In-Reply-To: <5227AE4F.8050603@kapsi.fi> X-Enigmail-Version: 1.4.6 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 09/04/2013 04:03 PM, Mikko Perttunen wrote: > On 09/04/2013 09:44 PM, Stephen Warren wrote: >> On 08/28/2013 09:48 AM, Mikko Perttunen wrote: >>> The Vdd regulator used to be enabled only at tegra_output_hdmi_enable, >>> which is called after a sink is detected. However, the HDMI hotplug pin >>> works by returning the voltage supplied by the Vdd pin, so this meant >>> that the hotplug pin was never asserted and the sink was not detected >>> unless the Vdd regulator was set to be always on. >>> >>> This patch moves the enable to the tegra_hdmi_drm_init function to make >>> sure the regulator will get enabled. >> >> The DT binding document isn't very clear on this topic (and should be >> fixed): What is this regulator intended to control? If this regulator >> solely controls the supply to the hotplug detection circuit, this change >> makes sense. If the regulator mainly supplies something else (e.g. part >> of the HDMI core on the Tegra chip), then perhaps this change isn't >> correct. The correct approach might be to introduce another (optional) >> regulator specifically for the hotplug circuit. Presumably both DT >> properties vdd-supply and hotplug-supply could point at the same >> regulator if that's the way the HW was wired up. >> -- >> To unsubscribe from this list: send the line "unsubscribe linux-tegra" in >> the body of a message to majordomo@vger.kernel.org >> More majordomo info at http://vger.kernel.org/majordomo-info.html >> > > AFAICT, it controls the Vdd pin on the HDMI port, so it just affects the > hotplug pin and the DDC I2C bus power. Ah OK, then this code change makes sense. It'd be useful to put what you just wrote into the binding doc.