From mboxrd@z Thu Jan 1 00:00:00 1970 From: Shilpa Bhat Subject: Re: [PATCH v2] cpufreq: powernv: Set the cpus to nominal frequency during reboot/kexec Date: Mon, 01 Sep 2014 11:35:59 +0530 Message-ID: <1409551559.13507.21.camel@localhost.localdomain> References: <1409234816-10802-1-git-send-email-shilpa.bhat@linux.vnet.ibm.com> <1409548719.13507.13.camel@localhost.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Return-path: Received: from e28smtp03.in.ibm.com ([122.248.162.3]:54733 "EHLO e28smtp03.in.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751195AbaIAGG7 (ORCPT ); Mon, 1 Sep 2014 02:06:59 -0400 Received: from /spool/local by e28smtp03.in.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Mon, 1 Sep 2014 11:36:56 +0530 In-Reply-To: Sender: linux-pm-owner@vger.kernel.org List-Id: linux-pm@vger.kernel.org To: Viresh Kumar Cc: Benjamin Herrenschmidt , "linuxppc-dev@lists.ozlabs.org" , "Rafael J. Wysocki" , "linux-pm@vger.kernel.org" , Linux Kernel Mailing List , Preeti U Murthy This patch ensures the cpus to kexec/reboot at nominal frequency. Nominal frequency is the highest cpu frequency on PowerPC at which the cores can run without getting throttled. If the host kernel had set the cpus to a low pstate and then it kexecs/reboots to a cpufreq disabled kernel it would cause the target kernel to perform poorly. It will also increase the boot up time of the target kernel. So set the cpus to high pstate, in this case to nominal frequency before rebooting to avoid such scenarios. The reboot notifier will set the cpus to nominal frequncy. Signed-off-by: Shilpasri G Bhat Suggested-by: Viresh Kumar Reviewed-by: Preeti U Murthy Acked-by: Viresh Kumar --- Changes v1->v2: Invoke .target() driver callback to set the cpus to nominal frequency in reboot notifier, instead of calling cpufreq_suspend() as suggested by Viresh Kumar. Modified the commit message. drivers/cpufreq/powernv-cpufreq.c | 35 +++++++++++++++++++++++++++++++++++ 1 file changed, 35 insertions(+) diff --git a/drivers/cpufreq/powernv-cpufreq.c b/drivers/cpufreq/powernv-cpufreq.c index 379c083..f8b83c8 100644 --- a/drivers/cpufreq/powernv-cpufreq.c +++ b/drivers/cpufreq/powernv-cpufreq.c @@ -26,6 +26,7 @@ #include #include #include +#include #include #include @@ -35,6 +36,7 @@ #define POWERNV_MAX_PSTATES 256 static struct cpufreq_frequency_table powernv_freqs[POWERNV_MAX_PSTATES+1]; +static bool rebooting; /* * Note: The set of pstates consists of contiguous integers, the @@ -284,6 +286,15 @@ static void set_pstate(void *freq_data) } /* + * get_nominal_index: Returns the index corresponding to the nominal + * pstate in the cpufreq table + */ +static inline unsigned int get_nominal_index(void) +{ + return powernv_pstate_info.max - powernv_pstate_info.nominal; +} + +/* * powernv_cpufreq_target_index: Sets the frequency corresponding to * the cpufreq table entry indexed by new_index on the cpus in the * mask policy->cpus @@ -293,6 +304,9 @@ static int powernv_cpufreq_target_index(struct cpufreq_policy *policy, { struct powernv_smp_call_data freq_data; + if (unlikely(rebooting && new_index != get_nominal_index())) + return -EBUSY; + freq_data.pstate_id = powernv_freqs[new_index].driver_data; /* @@ -317,6 +331,25 @@ static int powernv_cpufreq_cpu_init(struct cpufreq_policy *policy) return cpufreq_table_validate_and_show(policy, powernv_freqs); } +static int powernv_cpufreq_reboot_notifier(struct notifier_block *nb, + unsigned long action, void *unused) +{ + int cpu; + struct cpufreq_policy cpu_policy; + + rebooting = true; + for_each_online_cpu(cpu) { + cpufreq_get_policy(&cpu_policy, cpu); + powernv_cpufreq_target_index(&cpu_policy, get_nominal_index()); + } + + return NOTIFY_DONE; +} + +static struct notifier_block powernv_cpufreq_reboot_nb = { + .notifier_call = powernv_cpufreq_reboot_notifier, +}; + static struct cpufreq_driver powernv_cpufreq_driver = { .name = "powernv-cpufreq", .flags = CPUFREQ_CONST_LOOPS, @@ -342,12 +375,14 @@ static int __init powernv_cpufreq_init(void) return rc; } + register_reboot_notifier(&powernv_cpufreq_reboot_nb); return cpufreq_register_driver(&powernv_cpufreq_driver); } module_init(powernv_cpufreq_init); static void __exit powernv_cpufreq_exit(void) { + unregister_reboot_notifier(&powernv_cpufreq_reboot_nb); cpufreq_unregister_driver(&powernv_cpufreq_driver); } module_exit(powernv_cpufreq_exit); -- 1.9.3