From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from va3outboundpool.messaging.microsoft.com (va3ehsobe010.messaging.microsoft.com [216.32.180.30]) (using TLSv1 with cipher AES128-SHA (128/128 bits)) (Client CN "mail.global.frontbridge.com", Issuer "MSIT Machine Auth CA 2" (not verified)) by ozlabs.org (Postfix) with ESMTPS id 7BC972C00CE for ; Thu, 26 Sep 2013 03:57:06 +1000 (EST) Received: from mail141-va3 (localhost [127.0.0.1]) by mail141-va3-R.bigfish.com (Postfix) with ESMTP id A65AF440150 for ; Wed, 25 Sep 2013 17:57:01 +0000 (UTC) Received: from VA3EHSMHS008.bigfish.com (unknown [10.7.14.248]) by mail141-va3.bigfish.com (Postfix) with ESMTP id 01DD910004C for ; Wed, 25 Sep 2013 17:56:59 +0000 (UTC) Message-ID: <1380131815.24959.185.camel@snotra.buserror.net> Subject: Re: [PATCH v4 4/4] powerpc/85xx: add sysfs for pw20 state and altivec idle From: Scott Wood To: Wang Dongsheng-B40534 Date: Wed, 25 Sep 2013 12:56:55 -0500 In-Reply-To: References: <1380014925-23300-2-git-send-email-dongsheng.wang@freescale.com> <1380014925-23300-4-git-send-email-dongsheng.wang@freescale.com> <6A3DF150A5B70D4F9B66A25E3F7C888D0717F8F9@039-SN2MPN1-011.039d.mgd.msft.net> Content-Type: text/plain; charset="UTF-8" MIME-Version: 1.0 Cc: Wood Scott-B07421 , "linuxppc-dev@lists.ozlabs.org" , Bhushan Bharat-R65777 List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , 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.com@lists.ozlabs.org] On Behalf Of > > > bounces+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 > > > > > > 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 > > > --- > > > *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. > "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;" > > 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. You can test it by hacking a wrong timebase frequency in and seeing what the calculation does. Or do something like this: if (ns >= 10000) cycle = ((ns + 500) / 1000) * tb_ticks_per_usec; else cycle = div_u64((u64)ns * tb_ticks_per_usec, 1000); ...which can be tested just by varying ns. > If later there will be more than 1GHZ platform at that time to add this support. There almost certainly won't be timebases that run that fast, but divide by zero is a rather nasty way of responding if such a thing does happen. -Scott