On 14 August 2014 16:49, Shilpasri G Bhat
<shilpa.b...@linux.vnet.ibm.com> wrote:
> 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 suspend the cpufreq governor and enable
> nominal frequency to be set during a reboot/kexec similar to the
> suspend operartion.
>
> Signed-off-by: Shilpasri G Bhat <shilpa.b...@linux.vnet.ibm.com>
> Reviewed-by: Preeti U Murthy <pre...@linux.vnet.ibm.com>
> ---
> drivers/cpufreq/powernv-cpufreq.c | 16 ++++++++++++++++
> 1 file changed, 16 insertions(+)
>
> diff --git a/drivers/cpufreq/powernv-cpufreq.c
> b/drivers/cpufreq/powernv-cpufreq.c
> index 379c083..e9f3d3a 100644
> --- a/drivers/cpufreq/powernv-cpufreq.c
> +++ b/drivers/cpufreq/powernv-cpufreq.c
> @@ -26,6 +26,7 @@
> #include <linux/cpufreq.h>
> #include <linux/smp.h>
> #include <linux/of.h>
> +#include <linux/reboot.h>
>
> #include <asm/cputhreads.h>
> #include <asm/firmware.h>
> @@ -314,9 +315,21 @@ static int powernv_cpufreq_cpu_init(struct
> cpufreq_policy *policy)
> for (i = 0; i < threads_per_core; i++)
> cpumask_set_cpu(base + i, policy->cpus);
>
> + policy->suspend_freq = pstate_id_to_freq(powernv_pstate_info.nominal);
> return cpufreq_table_validate_and_show(policy, powernv_freqs);
> }
>
> +static int powernv_cpufreq_reboot_notifier(struct notifier_block *nb,
> + unsigned long action, void *unused)
> +{
> + cpufreq_suspend();
> + 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,
> @@ -325,6 +338,7 @@ static struct cpufreq_driver powernv_cpufreq_driver = {
> .target_index = powernv_cpufreq_target_index,
> .get = powernv_cpufreq_get,
> .attr = powernv_cpu_freq_attr,
> + .suspend = cpufreq_generic_suspend,
I couldn't understand why you have added a notifier here. This callback
by itself should be enough. Isn't it?
And then you have called cpufreq_suspend(), which is absolutely wrong,
from that notifier..
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
