Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932554Ab3IDSoh (ORCPT ); Wed, 4 Sep 2013 14:44:37 -0400 Received: from avon.wwwdotorg.org ([70.85.31.133]:55708 "EHLO avon.wwwdotorg.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755605Ab3IDSof (ORCPT ); Wed, 4 Sep 2013 14:44:35 -0400 Message-ID: <52277F90.40109@wwwdotorg.org> Date: Wed, 04 Sep 2013 12:44:32 -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: 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> In-Reply-To: <1377704922-2824-4-git-send-email-mperttunen@nvidia.com> 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 Content-Length: 1357 Lines: 24 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-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/