On Thu, 2013-09-26 at 01:18 -0500, Wang Dongsheng-B40534 wrote: > > > -----Original Message----- > > From: Bhushan Bharat-R65777 > > Sent: Thursday, September 26, 2013 12:23 PM > > To: Wang Dongsheng-B40534; Wood Scott-B07421 > > Cc: linuxppc-dev@lists.ozlabs.org > > Subject: RE: [PATCH v4 4/4] powerpc/85xx: add sysfs for pw20 state and > > altivec idle > > > > > > > > > -----Original Message----- > > > From: Wang Dongsheng-B40534 > > > Sent: Thursday, September 26, 2013 8:02 AM > > > To: Wood Scott-B07421 > > > Cc: Bhushan Bharat-R65777; linuxppc-dev@lists.ozlabs.org > > > Subject: RE: [PATCH v4 4/4] powerpc/85xx: add sysfs for pw20 state and > > > altivec idle > > > > > > > > > > > > > -----Original Message----- > > > > From: Wood Scott-B07421 > > > > Sent: Thursday, September 26, 2013 1:57 AM > > > > To: Wang Dongsheng-B40534 > > > > Cc: Bhushan Bharat-R65777; Wood Scott-B07421; linuxppc- > > > > d...@lists.ozlabs.org > > > > Subject: Re: [PATCH v4 4/4] powerpc/85xx: add sysfs for pw20 state > > > > and altivec idle > > > > > > > > On Wed, 2013-09-25 at 03:10 -0500, Wang Dongsheng-B40534 wrote: > > > > > > > > > > > -----Original Message----- > > > > > > From: Bhushan Bharat-R65777 > > > > > > Sent: Wednesday, September 25, 2013 2:23 PM > > > > > > To: Wang Dongsheng-B40534; Wood Scott-B07421 > > > > > > Cc: linuxppc-dev@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....@lists.ozlabs.org] On > > > > > > > bounces+Behalf Of Dongsheng > > > > > > > Wang > > > > > > > Sent: Tuesday, September 24, 2013 2:59 PM > > > > > > > To: Wood Scott-B07421 > > > > > > > Cc: linuxppc-dev@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.w...@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.w...@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? > > > > > > > > Actually it'll be a divide by zero in that case. > > > > > > > tb_ticks_per_usec = ppc_tb_freq / 1000000; Means TB freq should be > > > more than 1MHZ. > > > > > > if ppc_tb_freq less than 1000000, the tb_ticks_per_usec will be a > > > divide by zero. > > > If this condition is established, I think kernel cannot work as a > > normal. > > > > > > So I think we need to believe that the variable is not zero. > > > > We do believe it is non-zero but greater than 1000 :) > > > > > And I think TB freq > > > should not less than 1MHZ on PPC platform, because if TB freq less > > > than 1MHZ, the precision time will become very poor and system > > > response time will be slower. > > > > Not sure what you are describing here related to divide by zero we are > > mentioning. > > You are talking about if tb_ticks_per_usec is ZERO and we are talking > > about if (1000/tb_ticks_per_usec) will be zero. > > > > BTW, div_u64() handle the case where divider is zero.
How? When I checked yesterday it looked like div_u64() mapped to a hardware division on 64-bit targets. In any case it's not good to rely on such behavior. > cycle = div_u64(ns, 1000 / tb_ticks_per_usec); > For this, I think we were discussing the two issues: > > 1. Scott talking about, when the tb_ticks_per_usec is a zero. No I wasn't. I was talking about when tb_ticks_per_usec > 1000, and thus "1000 / tb_ticks_per_usec" is zero. You said that the result would be ns in that case. > 2. You are talking about 1000/tb_ticks_per_usec is a zero. > This situation is about TB freq > 1GHZ. > > I will fix this issue. Like I said before, > "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;"" > > #define TB_FREQ_1GHZ 1000 > > If (tb_ticks_per_usec > TB_FREQ_1GHZ) > cycle = ns * (tb_ticks_per_usec / 1000); > else > cycle = div_u64(ns, 1000 / tb_ticks_per_usec); > > how about this? :) I suggested an alternative to satisfy your complaint that it's hard to test one of those if/else branches. Plus, your version will be quite inaccurate if (e.g.) tb_ticks_per_usec is 501, or 1999. -Scott _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
