On Thu, Mar 30, 2017 at 04:56:52PM +0100, Sudeep Holla wrote:

[...]

quoted

+static struct pm_qos_request debug_qos_req;
+static int idle_constraint = PM_QOS_DEFAULT_VALUE;
+module_param(idle_constraint, int, 0600);
+MODULE_PARM_DESC(idle_constraint, "Latency requirement in microseconds for CPU "
+		 "idle states (default is -1, which means have no limiation "
+		 "to CPU idle states; 0 means disabling all idle states; user "
+		 "can choose other platform dependent values so can disable "
+		 "specific idle states for the platform)");
+

NACK for this. Why you want the policy inside the driver. You can always
do that from the user-space. I have mentioned it several times now.
What can't you do these ?

1. echo "what_ever_latency_you_need_in_uS" > /dev/cpu_dma_latency
2. echo 1 > /sys/devices/system/cpu/cpu$cpu/cpuidle/state$state/disable
   (for all cpus and their states) (1) is definitely simpler way to
    disable deeper idle if latency = 0uS

You can always warn user about that when it's enabled via debugfs/sysfs

Thanks for suggestion, now it's clear for me.

-- 
Regards,
Sudeep