Re: [PATCH] keystone: psci: adds cpu_die implementation

[Vitaly Andrianov]

On 06/25/2015 10:59 AM, santosh shilimkar wrote:
> On 6/25/2015 7:45 AM, Mark Rutland wrote:
> > Hi,
> >
> > On Thu, Jun 25, 2015 at 03:02:50PM +0100, Vitaly Andrianov wrote:
> > > This commit add cpu_die implementation using psci api
> >
> > I don't understand. If you have a PSCI implementation, it should be
> > sufficient to have a PSCI node (and enable-method) in your DT, and the
> > generic code will be used. Nothing should be required in your board
> > code.
> >
> > You should also use CPU_ON to bring secondaries online rather than
> > mixing up PSCI and platform-specific mechanisms.
> Good point about CPU_ON. We need that as well.
Does it mean that keystone_defconfig must always have CONFIG_HOTPLUG_CPU 
and CONFIG_ARM_PSCI enabled?

What is if someone doesn't want to have HOTPLUG_CPU?
How he can boot secondary CPU w/o platform-specific mechanizm?


> > > Signed-off-by: Vitaly Andrianov <vitalya@xxxxxx>
> > > ---
> > >   arch/arm/mach-keystone/platsmp.c | 32 ++++++++++++++++++++++++++++++++
> > >   1 file changed, 32 insertions(+)
> > >
> > > diff --git a/arch/arm/mach-keystone/platsmp.c
> > > b/arch/arm/mach-keystone/platsmp.c
> > > index 5f46a7c..2c40cc0 100644
> > > --- a/arch/arm/mach-keystone/platsmp.c
> > > +++ b/arch/arm/mach-keystone/platsmp.c
> > > @@ -20,6 +20,7 @@
> > >   #include <asm/prom.h>
> > >   #include <asm/tlbflush.h>
> > >   #include <asm/pgtable.h>
> > > +#include <asm/psci.h>
> > >
> > >   #include "keystone.h"
> > >
> > > @@ -51,7 +52,38 @@ static inline void __cpuinit
> > > keystone_smp_secondary_initmem(unsigned int cpu)
> > >   {}
> > >   #endif
> > >
> > > +
> > > +#ifdef CONFIG_HOTPLUG_CPU
> > > +static void keystone_cpu_die(unsigned int cpu)
> > > +{
> > > +#ifdef CONFIG_ARM_PSCI
> > > +    struct psci_power_state pwr_state = {0, 0, 0};
> > > +
> > > +    pr_info("keystone_cpu_die(%d) from %d using PSCI\n", cpu,
> > > +           smp_processor_id());
> > > +
> > > +    if (psci_ops.cpu_off)
> > > +        psci_ops.cpu_off(pwr_state);
> > > +#else
> > > +    /*
> > > +     * We may want to add here a direct smc call to monitor
> > > +     * if the kernel doesn't support PSCI API
> > > +     */
> > > +#endif
> >
> > You should determine this from your DT. Your FW/bootloader can patch in
> > the relevant nodes and properties when support is present, so the
> > presence of such nodes should guarantee that PSCI is available.
> That will be a nice trick. FW already does some tweaks of dts for
> LPAE/non_LPAE tweaks.
>
> Regards,
> Santosh

Thanks,
-Vitaly

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