From mboxrd@z Thu Jan 1 00:00:00 1970 From: Kevin Hilman Subject: Re: [PATCH 4/7] phy: meson: add USB2 PHY support for Meson8b and GXBB Date: Tue, 13 Sep 2016 17:59:11 -0700 Message-ID: <7hzinbmh40.fsf@baylibre.com> References: <20160904213152.25837-1-martin.blumenstingl@googlemail.com> <20160904213152.25837-5-martin.blumenstingl@googlemail.com> <1473780508.10237.22.camel@pengutronix.de> Mime-Version: 1.0 Content-Type: text/plain Return-path: In-Reply-To: (Martin Blumenstingl's message of "Tue, 13 Sep 2016 20:38:06 +0200") Sender: linux-usb-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Martin Blumenstingl Cc: Philipp Zabel , hdegoede-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, Ben Dooks , mark.rutland-5wv7dgnIgG8@public.gmane.org, devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, gregkh-hQyY1W1yCW8ekmWlsbkhG0B+6BGkLq7r@public.gmane.org, johnyoun-HKixBCOQz3hWk0Htik3J/w@public.gmane.org, will.deacon-5wv7dgnIgG8@public.gmane.org, mturquette-rdvid1DuHRBWk0Htik3J/w@public.gmane.org, linux-usb-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, sboyd-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org, kishon-l0cyMroinI0@public.gmane.org, robh+dt-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org, catalin.marinas-5wv7dgnIgG8@public.gmane.org, carlo-KA+7E9HrN00dnm+yROfE0A@public.gmane.org, linux-amlogic-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, linux-clk-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, jbrunet-rdvid1DuHRBWk0Htik3J/w@public.gmane.org List-Id: devicetree@vger.kernel.org Martin Blumenstingl writes: > On Tue, Sep 13, 2016 at 5:28 PM, Philipp Zabel wrote: [...] >>> I added Philipp and Hans to this thread - maybe they can comment on this. >>> To sum it up, our problem is: >>> - there are two separate USB PHYs on Meson GXBB >>> - both are sharing the same reset line (provided by the reset-meson driver) >>> - during initialization of the PHYs we must only call >>> reset_control_reset(rstc) once (if we do it for the first *and* second >>> PHY then the first PHY gets confused once the second PHY uses the >>> reset because the first PHY's state is reset as well) >> >> If you have an initially asserted reset line and you can enable the >> first module by deasserting the reset via reset_control_deassert (and >> reset_control_assert to signal when the module may be disabled again >> after use), shared resets are for you. >> >> If you need a reset pulse or have no direct control over the reset line, >> (device_reset), the reset framework currently has no solution for this. >> The ugly thing about reset_control_once would be that it can't re-reset >> modules when unloading and reloading driver modules. > > The corresponding reset driver in question is reset-meson, which only > implements reset (assert/deassert are not implemented). However, I > don't know if this is due to hardware design. > I think the hardware implements the latter, but maybe Neil can give > more information here (I currently don't have access to my board so I > cannot test how the hardware actually behaves). It's implemented that way because the hardware only supports a reset pulse. Kevin -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html