From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephen Warren Subject: Re: [PATCH v2 3/6] host1x: hdmi: Enable Vdd earlier for hotplug/DDC Date: Wed, 04 Sep 2013 16:24:26 -0600 Message-ID: <5227B31A.3070404@wwwdotorg.org> 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> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <5227AE4F.8050603-/1wQRMveznE@public.gmane.org> Sender: linux-tegra-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Mikko Perttunen Cc: Mikko Perttunen , thierry.reding-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org, tbergstrom-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org, dri-devel-PD4FTy7X32lNgt0PjOBp9y5qC8QIuHrW@public.gmane.org, linux-tegra-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-tegra@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-u79uwXL29TY76Z2rM5mHXA@public.gmane.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.