> -----Original Message----- > From: linux-tegra-ow...@vger.kernel.org [mailto:linux-tegra- > ow...@vger.kernel.org] On Behalf Of Stephen Warren > Sent: Thursday, April 04, 2013 12:38 AM > To: Venu Byravarasu > Cc: gre...@linuxfoundation.org; ba...@ti.com; > st...@rowland.harvard.edu; linux-te...@vger.kernel.org; linux- > u...@vger.kernel.org; linux-ker...@vger.kernel.org > Subject: Re: [PATCH v2 1/7] ARM: tegra: finalize USB EHCI and PHY bindings > > On 04/03/2013 02:41 AM, Venu Byravarasu wrote: > > The existing Tegra USB bindings have a few issues: > ... > > This patch fixes the binding definition to resolve these issues. > > > diff --git a/Documentation/devicetree/bindings/usb/nvidia,tegra20-usb- > phy.txt b/Documentation/devicetree/bindings/usb/nvidia,tegra20-usb- > phy.txt > > > Required properties : > ... > > + - vbus-supply: regulator for VBUS > > Doesn't the driver only need to control VBUS if the port is in OTG mode? > > If there is no VBUS control, and the HW provides VBUS, I think that the > port can only operate in host mode. > > If there is no VBUS control, and the HW does not provide VBUS, I think > that the port can only operate in peripheral mode. > > If there is VBUS control, then shouldn't the port always operate in OTG > mode, or are there other reasons to control VBUS even in host-only mode? > > If VBUS control is only useful for OTG mode, then I think the > vbus-supply property should be documented in a "Required properties for > dr_mode == otg" section.
Agree, will do it in next patch update. > > I assume that VBUS control makes no sense for a peripheral-mode-only > port, so if VBUS control is useful for host-only mode as well as OTG > mode, then I think the vbus-supply property should be documented in a > "Required properties for dr_mode != peripheral" section. > > Is the following table correct? > > Port operating mode: host peripheral otg > -------------------- ---- ---------- --- > VBUS control required: no no yes > VBUS control useful: yes[1]? no yes > > [1] perhaps for power-saving/suspend??? For waking system up from sleep via devices connected to USB, I think Vbus is always kept ON in host mode. > -- > To unsubscribe from this list: send the line "unsubscribe linux-tegra" in > the body of a message to majord...@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
