On Thu, Nov 07, 2013 at 11:34:51AM -0600, Scott Wood wrote: > On Thu, 2013-11-07 at 15:17 +0800, Kevin Hao wrote: > > It makes no sense to initialize the mpic ipi for the SoC which has > > doorbell support. So set the smp_85xx_ops.probe to NULL for this > > case. Since the smp_85xx_ops.probe is also used in function > > smp_85xx_setup_cpu() to check if we need to invoke > > mpic_setup_this_cpu(), we introduce a new setup_cpu function > > smp_85xx_basic_setup() to remove this dependency. > > Is there any harm caused by setting up the IPIs?
No real harm. Just make no sense to do so and it does cause confusion when you cat /proc/interrupts and get something like this: 507: 0 0 OpenPIC 2043 Edge ipi call function 508: 0 0 OpenPIC 2044 Edge ipi reschedule 509: 0 0 OpenPIC 2045 Edge ipi call function single DBL: 7053 10137 Doorbell interrupts > > What about other MPIC setup, such as setting the current task priority > register? This is done by the invoking of function mpic_setup_this_cpu() in smp_85xx_setup_cpu(). > BTW, what exactly is probe() supposed to be doing? It is supposed to do the platform specific smp initialization and then return the CPU count. > It looks like its > main effect (with smp_mpic_probe) is to request IPIs, but the caller > seems to treat it mainly as a way to determine CPU count. > > I looked at the caller of .probe() (which is smp_prepare_cpus()) to see > what happens when probe is NULL, and the handling of max_cpus doesn't > make much sense. At first I was concerned by the gratuitous difference > between smp_mpic_probe() using cpu_possible_mask versus > smp_prepare_cpus() using NR_CPUS, but the value isn't even used (all the > code that consumed max_cpus after setting it has been removed), and the > value passed in to smp_prepare_cpus() is ignored. Yes, the return value of .probe makes no sense now. Actually there is already a patch to remove the check of the return value of .probe in function smp_prepare_cpus(). http://patchwork.ozlabs.org/patch/260574/ Thanks, Kevin > > -Scott > > >
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