From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from ozlabs.org (ozlabs.org [IPv6:2401:3900:2:1::2]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id AA9D81A0D83 for ; Tue, 12 Jan 2016 21:57:51 +1100 (AEDT) Received: from e28smtp06.in.ibm.com (e28smtp06.in.ibm.com [125.16.236.6]) (using TLSv1 with cipher CAMELLIA256-SHA (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id DF0151402D9 for ; Tue, 12 Jan 2016 21:57:50 +1100 (AEDT) Received: from localhost by e28smtp06.in.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Tue, 12 Jan 2016 16:27:48 +0530 Received: from d28relay02.in.ibm.com (d28relay02.in.ibm.com [9.184.220.59]) by d28dlp02.in.ibm.com (Postfix) with ESMTP id 7DF423940064 for ; Tue, 12 Jan 2016 16:27:45 +0530 (IST) Received: from d28av01.in.ibm.com (d28av01.in.ibm.com [9.184.220.63]) by d28relay02.in.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id u0CAvfOI52953160 for ; Tue, 12 Jan 2016 16:27:41 +0530 Received: from d28av01.in.ibm.com (localhost [127.0.0.1]) by d28av01.in.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id u0CAvds2005848 for ; Tue, 12 Jan 2016 16:27:40 +0530 Message-ID: <5694DC21.5000009@linux.vnet.ibm.com> Date: Tue, 12 Jan 2016 16:27:37 +0530 From: Shreyas B Prabhu MIME-Version: 1.0 To: Shilpasri G Bhat CC: linuxppc-dev@ozlabs.org, linux-kernel@vger.kernel.org, rjw@rjwysocki.net, viresh.kumar@linaro.org, linux-pm@vger.kernel.org, pc@us.ibm.com, anton@samba.org, ego@linux.vnet.ibm.com Subject: Re: [PATCH RESEND v4 1/4] cpufreq: powernv: Remove cpu_to_chip_id() from hot-path References: <1452594267-12844-1-git-send-email-shilpa.bhat@linux.vnet.ibm.com> <1452594267-12844-2-git-send-email-shilpa.bhat@linux.vnet.ibm.com> In-Reply-To: <1452594267-12844-2-git-send-email-shilpa.bhat@linux.vnet.ibm.com> Content-Type: text/plain; charset=windows-1252 List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On 01/12/2016 03:54 PM, Shilpasri G Bhat wrote: > cpu_to_chip_id() does a DT walk through to find out the chip id by taking a > contended device tree lock. This adds an unnecessary overhead in a hot-path. > So instead of cpu_to_chip_id() use PIR of the cpu to find the chip id. > > Reported-by: Anton Blanchard > Signed-off-by: Shilpasri G Bhat > --- > drivers/cpufreq/powernv-cpufreq.c | 7 +++++-- > 1 file changed, 5 insertions(+), 2 deletions(-) > > diff --git a/drivers/cpufreq/powernv-cpufreq.c b/drivers/cpufreq/powernv-cpufreq.c > index cb50138..597a084 100644 > --- a/drivers/cpufreq/powernv-cpufreq.c > +++ b/drivers/cpufreq/powernv-cpufreq.c > @@ -39,6 +39,7 @@ > #define PMSR_PSAFE_ENABLE (1UL << 30) > #define PMSR_SPR_EM_DISABLE (1UL << 31) > #define PMSR_MAX(x) ((x >> 32) & 0xFF) > +#define pir_to_chip_id(pir) (((pir) >> 7) & 0x3f) Since this is platform specific and true only for power8, this is not the right place to put it. Either you can move this to arch/powerpc or you can maintain a cpu to chip map within the driver. > > static struct cpufreq_frequency_table powernv_freqs[POWERNV_MAX_PSTATES+1]; > static bool rebooting, throttled, occ_reset; > @@ -312,13 +313,14 @@ static inline unsigned int get_nominal_index(void) > static void powernv_cpufreq_throttle_check(void *data) > { > unsigned int cpu = smp_processor_id(); > + unsigned int chip_id = pir_to_chip_id(hard_smp_processor_id()); > unsigned long pmsr; > int pmsr_pmax, i; > > pmsr = get_pmspr(SPRN_PMSR); > > for (i = 0; i < nr_chips; i++) > - if (chips[i].id == cpu_to_chip_id(cpu)) > + if (chips[i].id == chip_id) > break; > > /* Check for Pmax Capping */ > @@ -558,7 +560,8 @@ static int init_chip_info(void) > unsigned int prev_chip_id = UINT_MAX; > > for_each_possible_cpu(cpu) { > - unsigned int id = cpu_to_chip_id(cpu); > + unsigned int id = > + pir_to_chip_id(get_hard_smp_processor_id(cpu)); > > if (prev_chip_id != id) { > prev_chip_id = id; > Thanks, Shreyas