[PATCH v4 4/4] powerpc/85xx: add sysfs for pw20 state and altivec idle

[Bhushan Bharat-R65777]

> -----Original Message-----
> From: Wang Dongsheng-B40534
> Sent: Wednesday, September 25, 2013 1:40 PM
> To: Bhushan Bharat-R65777; Wood Scott-B07421
> Cc: linuxppc-dev at lists.ozlabs.org
> Subject: RE: [PATCH v4 4/4] powerpc/85xx: add sysfs for pw20 state and altivec
> idle
> 
> 
> 
> > -----Original Message-----
> > From: Bhushan Bharat-R65777
> > Sent: Wednesday, September 25, 2013 2:23 PM
> > To: Wang Dongsheng-B40534; Wood Scott-B07421
> > Cc: linuxppc-dev at lists.ozlabs.org; Wang Dongsheng-B40534
> > Subject: RE: [PATCH v4 4/4] powerpc/85xx: add sysfs for pw20 state and
> > altivec idle
> >
> >
> >
> > > -----Original Message-----
> > > From: Linuxppc-dev [mailto:linuxppc-dev-
> > > bounces+bharat.bhushan=freescale.com at lists.ozlabs.org] On Behalf Of
> > > bounces+Dongsheng
> > > Wang
> > > Sent: Tuesday, September 24, 2013 2:59 PM
> > > To: Wood Scott-B07421
> > > Cc: linuxppc-dev at lists.ozlabs.org; Wang Dongsheng-B40534
> > > Subject: [PATCH v4 4/4] powerpc/85xx: add sysfs for pw20 state and
> > > altivec idle
> > >
> > > From: Wang Dongsheng <dongsheng.wang at freescale.com>
> > >
> > > Add a sys interface to enable/diable pw20 state or altivec idle, and
> > > control the wait entry time.
> > >
> > > Enable/Disable interface:
> > > 0, disable. 1, enable.
> > > /sys/devices/system/cpu/cpuX/pw20_state
> > > /sys/devices/system/cpu/cpuX/altivec_idle
> > >
> > > Set wait time interface:(Nanosecond)
> > > /sys/devices/system/cpu/cpuX/pw20_wait_time
> > > /sys/devices/system/cpu/cpuX/altivec_idle_wait_time
> > > Example: Base on TBfreq is 41MHZ.
> > > 1~47(ns): TB[63]
> > > 48~95(ns): TB[62]
> > > 96~191(ns): TB[61]
> > > 192~383(ns): TB[62]
> > > 384~767(ns): TB[60]
> > > ...
> > >
> > > Signed-off-by: Wang Dongsheng <dongsheng.wang at freescale.com>
> > > ---
> > > *v4:
> > > Move code from 85xx/common.c to kernel/sysfs.c.
> > >
> > > Remove has_pw20_altivec_idle function.
> > >
> > > Change wait "entry_bit" to wait time.
> > >
> > >  arch/powerpc/kernel/sysfs.c | 291
> > > ++++++++++++++++++++++++++++++++++++++++++++
> > >  1 file changed, 291 insertions(+)
> > >
> > > diff --git a/arch/powerpc/kernel/sysfs.c
> > > b/arch/powerpc/kernel/sysfs.c index 27a90b9..23fece6 100644
> > > --- a/arch/powerpc/kernel/sysfs.c
> > > +++ b/arch/powerpc/kernel/sysfs.c
> > > @@ -85,6 +85,279 @@ __setup("smt-snooze-delay=",
> > > setup_smt_snooze_delay);
> > >
> > >  #endif /* CONFIG_PPC64 */
> > >
> > > +#ifdef CONFIG_FSL_SOC
> > > +#define MAX_BIT		63
> > > +
> > > +static u64 pw20_wt;
> > > +static u64 altivec_idle_wt;
> > > +
> > > +static unsigned int get_idle_ticks_bit(u64 ns) {
> > > +	u64 cycle;
> > > +
> > > +	cycle = div_u64(ns, 1000 / tb_ticks_per_usec);
> >
> > When tb_ticks_per_usec  > 1000 (timebase frequency > 1GHz) then this
> > will always be ns, which is not correct, no?
> >
> "1000 / tb_ticks_per_usec" means nsec_ticks_per_tb
> 
> If timebase frequency > 1GHz, this should be "tb_ticks_per_usec / 1000" and to
> get tb_ticks_per_nsec.
> This should be changed to "cycle = ns * tb_ticks_per_nsec;"

Yes, we need to change this to two line.

> 
> But at present we do not have such a platform that timebase frequency more than
> 1GHz. And I think it is not need to support such a situation. Because we have no
> environment to test it.
> 
> If later there will be more than 1GHZ platform at that time to add this support.

Would like to leave it to Scott, but personally I think that if there is something simple to fix then it must be fixed rather than waiting for some error to happen and then fixing.

-Bharat

> 
> Thanks.
> 
> -dongsheng