On 11/5/2015 3:14 PM, Linus Walleij wrote: > On Thu, Nov 5, 2015 at 6:51 AM, Kapil Hali <kapilh@xxxxxxxxxxxx> wrote: > >> Add SMP support for Broadcom's Northstar Plus SoC, >> cpu enable method and pen_release procedures. This >> changes also consolidates iProc family's - BCM NSP >> and BCM Kona, SMP handling in a common file. >> >> Northstar Plus SoC is based on ARM Cortex-A9 >> revision r3p0 which requires configuration for ARM >> Errata 764369 for SMP. This change adds the needed >> configuration option. >> >> Signed-off-by: Kapil Hali <kapilh@xxxxxxxxxxxx> > (...) >> +/* >> + * iProc specific entry point for secondary CPUs. This provides >> + * a "holding pen" into which all secondary cores are held until >> + * we are ready for them to initialise. >> + */ > > Do you *REALLY* need the complex pen hold/release semaphore > stuff? > > Consult for example commit > c00def71efd919e8ae835a25f4f4c80a4b2d36d3 > "ARM: ux500: simplify secondary CPU boot" > > I realized the pen hold/release stuff was totally surplus on the > ux500 platform, it was probably just copied from the Vexpress > or RealView reference design and kept around because ARM > did things that way. And you are copying the same code from > other platforms again. Do you *really* understand the pen hold/release > code? (I don't.) > > In our case it turned out that all that was really needed was: > > - Map and enable SCU at .smp_prepare_cpus() > > - Write the start address for the secondary CPU(s) in their > magic registers/addresses i.e what you do in > nsp_write_lut() and then call > arch_send_wakeup_ipi_mask(cpumask_of(cpu)); in > .smp_boot_secondary() > It seems you may not even need the IPI, I can't see > that call in your patch so I guess your secondary > CPUs aren't in WFI at boot. > There is a dsb_sev() to get secondary core out of standby. However, I think arch_send_wakeup_ipi_mask() is a better way as it is per core. I will make the required changes in the next patch set. > No pen hold/release magic! Works like a charm for us. > So see of you really need this horror story with copied > assembly code from realview etc. > > Yours, > Linus Walleij > Thanks, Kapil Hali -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
