From mboxrd@z Thu Jan 1 00:00:00 1970 From: Julien Grall Subject: Re: [PATCH v4] xen/arm: Add a clock property Date: Wed, 20 Jul 2016 13:10:14 +0100 Message-ID: <04d9dbfb-196d-a775-7fbb-526aba8085f4@arm.com> References: <1468309605-19522-1-git-send-email-dirk.behme@de.bosch.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: devicetree-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Geert Uytterhoeven Cc: Dirk Behme , "linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org" , Mark Rutland , Michael Turquette , xen-devel-GuqFBffKawtpuQazS67q72D2FQJk+8+b@public.gmane.org, "devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , Stefano Stabellini , linux-clk , Stephen Boyd List-Id: devicetree@vger.kernel.org On 20/07/16 12:49, Geert Uytterhoeven wrote: > Hi Julien, > > On Wed, Jul 20, 2016 at 1:01 PM, Julien Grall wrote: >> On 20/07/16 10:43, Geert Uytterhoeven wrote: >>> On Tue, Jul 12, 2016 at 9:46 AM, Dirk Behme >>> wrote: >>>> >>>> Clocks described by this property are reserved for use by Xen, and the OS >>>> must not alter their state any way, such as disabling or gating a clock, >>>> or modifying its rate. Ensuring this may impose constraints on parent >>>> clocks or other resources used by the clock tree. >>>> >>>> This property is used to proxy clocks for devices Xen has taken ownership >>>> of, such as UARTs, for which the associated clock controller(s) remain >>>> under the control of Dom0. >>> >>> >>> I'm not familiar with using XEN at all, but I'm a bit puzzled... >>> >>> Can't you just add a clocks property to the (virtual) serial device node >>> in DT? >>> Then the (virtual) serial device driver can get and enable the clock? >> >> There is no DT node for the Xen console (hvc). The UART used by Xen will be >> completely removed from the Device tree. > > Why is it removed? Because the device is used exclusively by Xen and DOM0 should not touch it at all (IRQs and MMIOs are not mapped). Regards, -- Julien Grall -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html