[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [RFC V2] xen: interface: introduce pvclk interface
Hi Ian, Stefano On Wed, Jan 20, 2016 at 12:27:07PM +0000, Ian Campbell wrote: >On Wed, 2016-01-20 at 12:06 +0000, Stefano Stabellini wrote: >> On Wed, 20 Jan 2016, Peng Fan wrote: >> > To my use case, Dom0 and DomU both use device tree, I need to build >> > the mapping table between id and name, since I use name to lookup >> > the clk in backend, like this: >> > "clk = __clk_loopkup(clkname); clk_prepare_enable(clk)". Maybe ACPI >> > is another different case. >> >> Theoretically on systems using ACPI there is no need to fiddle with >> clocks, > >I mentioned ACPI in my replies to v1 more as a placeholder for "other >firmware descriptions than DT", in order that the pv protocol we end up >with does not end up being DT specific, which would be a mistake >irrespective of what may or may not be required for non-DT firmware >descriptions. Thanks for clarifying. Beside this, are you ok with the xenstore node description in this file? Thanks, Peng. > >Ian. > >> see >> >> Documentation/arm64/arm-acpi.txt >> >> >> "In DT, clocks need to be specified >> and the drivers need to take them into account. In ACPI, the assumption >> is that UEFI will leave the device in a reasonable default state, >> including >> any clock settings. If for some reason the driver needs to change a >> clock >> value, this can be done in an ACPI method; all the driver needs to do is >> invoke the method and not concern itself with what the method needs to do >> to change the clock. Changing the hardware can then take place over time >> by changing what the ACPI method does, and not the driver. >> >> In DT, the parameters needed by the driver to set up clocks as in the >> example >> above are known as "bindings"; in ACPI, these are known as "Device >> Properties" >> and provided to a driver via the _DSD object." >> >> >> However currently we don't have the ability to run ACPI in DomU guests >> on ARM. Even if we had, there is no way to call native ACPI methods from >> any guests other than Dom0, even on x86. We just have to hope that >> clocks don't need to be reset on ACPI systems. _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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