For SMP, Is platform specific secondary startup functionreally needed?

John Linn John.Linn at xilinx.com
Wed Apr 6 12:40:31 EDT 2011


> -----Original Message-----
> From: Catalin Marinas [mailto:catalin.marinas at arm.com]
> Sent: Wednesday, April 06, 2011 10:36 AM
> To: John Linn
> Cc: linux at arm.linux.org.uk; linux-arm-kernel at lists.infradead.org
> Subject: RE: For SMP, Is platform specific secondary startup
> functionreally needed?
> 
> On Wed, 2011-04-06 at 15:42 +0100, John Linn wrote:
> > > On Wed, 2011-04-06 at 14:48 +0100, John Linn wrote:
> > > > I'm doing some cleanup of SMP patches based on Russell and
> Catalin's
> > > > input which was real helpful. It seems to me that there is not
> always a
> > > > need for a platform specific secondary startup.
> > > >
> > > > I have tested with just letting CPU1 go straight to
> secondary_startup()
> > > > in head.S and it works fine.
> > > >
> > > > I'm probably missing something obvious, if so can you share it?
> > >
> > > We use the pen release mechanism serialise the secondary CPUs
> booting.
> >
> > I'm not saying you can't have it, just that some platforms may not
> need
> > it.
> >
> > Maybe I'm oversimplifying the boot process for our platform, but it
> > seems to be working fine.
> 
> I haven't looked at your code in detail. Does this platform only have
> two cores? If that's the case, you should be fine.

Yes we’re only using 2 cores.  Sounds good as I prefer simple when possible.
I'll put out a new version of patches with this simplified approach.

> 
> But if you have more than one core and you don't serialise the entry to
> secondary_startup(), the __cpu_up() function may get confused.
> 

Understood, more complexity needed for more than 2 cores, makes sense.

Thanks for your time and input,
John

> --
> Catalin
> 
> 


This email and any attachments are intended for the sole use of the named recipient(s) and contain(s) confidential information that may be proprietary, privileged or copyrighted under applicable law. If you are not the intended recipient, do not read, copy, or forward this email message or any attachments. Delete this email message and any attachments immediately.


More information about the linux-arm-kernel mailing list