From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mikko Perttunen Subject: Re: [PATCH v2 3/6] host1x: hdmi: Enable Vdd earlier for hotplug/DDC Date: Thu, 05 Sep 2013 01:03:59 +0300 Message-ID: <5227AE4F.8050603@kapsi.fi> References: <1377704922-2824-1-git-send-email-mperttunen@nvidia.com> <1377704922-2824-4-git-send-email-mperttunen@nvidia.com> <52277F90.40109@wwwdotorg.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <52277F90.40109-3lzwWm7+Weoh9ZMKESR00Q@public.gmane.org> Sender: linux-tegra-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Stephen Warren 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 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.