lkml.org 
[lkml]   [2013]   [Apr]   [25]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [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
*
*/


\
 
 \ /
  Last update: 2013-04-25 14:41    [W:0.219 / U:0.644 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site