From mboxrd@z Thu Jan 1 00:00:00 1970 From: julien.grall@arm.com (Julien Grall) Date: Wed, 20 Jul 2016 13:10:14 +0100 Subject: [PATCH v4] xen/arm: Add a clock property In-Reply-To: References: <1468309605-19522-1-git-send-email-dirk.behme@de.bosch.com> Message-ID: <04d9dbfb-196d-a775-7fbb-526aba8085f4@arm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.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