From mboxrd@z Thu Jan 1 00:00:00 1970 From: Julien Grall Subject: Re: [PATCH v2] xen/arm: register clocks used by the hypervisor Date: Tue, 5 Jul 2016 15:02:19 +0100 Message-ID: <577BBDEB.7000305@arm.com> References: <1467282752-14053-1-git-send-email-dirk.behme@de.bosch.com> <577BBC1A.8020209@arm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <577BBC1A.8020209-5wv7dgnIgG8@public.gmane.org> Sender: devicetree-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Stefano Stabellini , Dirk Behme Cc: linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, Mark Rutland , devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, xen-devel-GuqFBffKawtpuQazS67q72D2FQJk+8+b@public.gmane.org, linux-clk-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Michael Turquette , Stephen Boyd List-Id: devicetree@vger.kernel.org On 05/07/16 14:54, Julien Grall wrote: > > > On 05/07/16 14:53, Stefano Stabellini wrote: >> On Thu, 30 Jun 2016, Dirk Behme wrote: >>> +- clocks: one or more clocks to be registered. >>> + Xen hypervisor drivers might replace native drivers, resulting in >>> + clocks not registered by these native drivers. To avoid that these >>> + unregistered clocks are disabled, then, e.g. by clk_disable_unused(), >>> + register them in the hypervisor node. >>> + An example for this are the clocks of the serial driver. If the >>> clocks >>> + used by the serial hardware interface are not registered by the >>> serial >>> + driver the serial output might stop once clk_disable_unused() is >>> called. >> >> What if we use the "status" property of the clocks? Could we set it to >> "disabled" in Xen? Would that be enough for Linux to leave them alone? > > clocks could be shared between multiple devices. So it is not possible > to disable the clock. To give an example, below the UART node for juno (arch/arm64/boot/dts/arm/juno-base.dtsi): soc_uart0: uart@7ff80000 { compatible = "arm,pl011", "arm,primecell"; reg = <0x0 0x7ff80000 0x0 0x1000>; interrupts = ; clocks = <&soc_uartclk>, <&soc_refclk100mhz>; clock-names = "uartclk", "apb_pclk"; }; The clock soc_refclk100mhz is shared with the mailbox. 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