linux-kernel - Re: [PATCH] cpufreq: powernv: Register the driver with reboot notifier

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Date:	Mon, 25 Aug 2014 16:11:21 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	Preeti U Murthy <preeti@...ux.vnet.ibm.com>
Cc:	Shilpasri G Bhat <shilpabhatppc@...il.com>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Shilpasri G Bhat <shilpa.bhat@...ux.vnet.ibm.com>,
	"linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>
Subject: Re: [PATCH] cpufreq: powernv: Register the driver with reboot notifier

On 25 August 2014 16:00, Viresh Kumar <viresh.kumar@...aro.org> wrote:
> Its not that I am doubting if this will work or not. But this Hack is using
> routines not meant for this purpose. And that being a core routine,
> things aren't that straightforward anymore.

Well if you want a working HACK for solving this, what about following ?

diff --git a/drivers/cpufreq/powernv-cpufreq.c
b/drivers/cpufreq/powernv-cpufreq.c
index af49688..d6a1742 100644
--- a/drivers/cpufreq/powernv-cpufreq.c
+++ b/drivers/cpufreq/powernv-cpufreq.c
@@ -34,6 +34,7 @@
 #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
@@ -283,6 +284,9 @@ static int powernv_cpufreq_target_index(struct
cpufreq_policy *policy,
 {
        struct powernv_smp_call_data freq_data;

+       if (unlikely(rebooting))
+               return -EBUSY;
+
        freq_data.pstate_id = powernv_freqs[new_index].driver_data;

        /*
@@ -317,6 +321,19 @@ static struct cpufreq_driver powernv_cpufreq_driver = {
        .attr           = powernv_cpu_freq_attr,
 };

+static int powernv_cpufreq_reboot_notifier(struct notifier_block *nb,
+               unsigned long action, void *unused)
+{
+       /* TODO: Get policy & index */
+       powernv_cpufreq_target_index(policy, index);
+       rebooting = true;
+       return NOTIFY_DONE;
+}
+
+static struct notifier_block powernv_cpufreq_reboot_nb = {
+       .notifier_call = powernv_cpufreq_reboot_notifier,
+};
+
 static int __init powernv_cpufreq_init(void)
 {
        int rc = 0;
@@ -328,12 +345,15 @@ static int __init powernv_cpufreq_init(void)
                return rc;
        }

-       return cpufreq_register_driver(&powernv_cpufreq_driver);
+       rc = cpufreq_register_driver(&powernv_cpufreq_driver);
+       register_reboot_notifier(&powernv_cpufreq_reboot_nb);
+       return rc;
 }
 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);
--
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