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Date: Thu, 25 Apr 2013 12:08:02 +0100 From: Stefano Stabellini <stefano.stabellini@...citrix.com> To: Will Deacon <will.deacon@....com> CC: Stefano Stabellini <Stefano.Stabellini@...citrix.com>, "xen-devel@...ts.xensource.com" <xen-devel@...ts.xensource.com>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org>, "arnd@...db.de" <arnd@...db.de>, "nicolas.pitre@...aro.org" <nicolas.pitre@...aro.org>, "rob.herring@...xeda.com" <rob.herring@...xeda.com>, "linux@....linux.org.uk" <linux@....linux.org.uk>, "olof@...om.net" <olof@...om.net> Subject: Re: [PATCH v8 1/2] arm: introduce psci_smp_ops On Thu, 25 Apr 2013, Will Deacon wrote: > On Thu, Apr 25, 2013 at 11:12:54AM +0100, Stefano Stabellini wrote: > > On Thu, 25 Apr 2013, Will Deacon wrote: > > > > +/* > > > > + * cpu_suspend Suspend the execution on a CPU > > > > + * @state we don't currently describe affinity levels, so just pass 0. > > > > + * @entry_point the first instruction to be executed on return > > > > + * returns 0 success, < 0 on failure > > > > + * > > > > + * cpu_off Power down a CPU > > > > + * @state we don't currently describe affinity levels, so just pass 0. > > > > + * no return on successful call > > > > + * > > > > + * cpu_on Power up a CPU > > > > + * @cpuid cpuid of target CPU, as from MPIDR > > > > + * @entry_point the first instruction to be executed on return > > > > + * returns 0 success, < 0 on failure > > > > + * > > > > + * migrate Migrate the context to a different CPU > > > > + * @cpuid cpuid of target CPU, as from MPIDR > > > > + * returns 0 success, < 0 on failure > > > > + * > > > > + */ > > > > > > Can you move these comments into psci-smp.c please? They're really specific > > > to the implementation there, and if we put them in a header we're lying to > > > ourselves about the parameters actually described by the PSCI specification. > > > > You have a good point about the PSCI spec. > > > > However from the Linux POV these comments should regard the functions > > exported by psci_operations, not the firmware interface, this is why I > > think it makes sense to keep them in psci.h. > > What we are saying is for example that psci_operations.cpu_on returns 0 > > on success and < 0 on failure, and it takes a cpuid and an entry point > > as parameters. We are not saying anything about the firmware interface. > > I disagree. You're explicitly stating that we pass the `cpuid of target CPU, > as from MPIDR'. That's simply not true -- the firmware could choose any > numbering scheme to identify the CPUs. For KVM and Xen, it *is* the mpidr, > which is why psci-smp.c works at all, but that's where the comment belongs, > not in this header file. I see, you want to keep psci_operations true to the firmware interface while explaining that psci_smp makes some assumptions about it. So the comment should be something like: /* * psci_smp assumes that the following is true about PSCI: * * cpu_suspend Suspend the execution on a CPU * @state we don't currently describe affinity levels, so just pass 0. * @entry_point the first instruction to be executed on return * returns 0 success, < 0 on failure * * cpu_off Power down a CPU * @state we don't currently describe affinity levels, so just pass 0. * no return on successful call * * cpu_on Power up a CPU * @cpuid cpuid of target CPU, as from MPIDR * @entry_point the first instruction to be executed on return * returns 0 success, < 0 on failure * * migrate Migrate the context to a different CPU * @cpuid cpuid of target CPU, as from MPIDR * returns 0 success, < 0 on failure * */ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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