Viresh,
On Fri, May 16, 2014 at 9:51 PM, Viresh Kumar viresh.kumar@linaro.org wrote:
+1.7 get_intermediate and target_intermediate +--------------------------------------------
+Only for drivers with target_index() and CPUFREQ_ASYNC_NOTIFICATION unset.
+get_intermediate should return a stable intermediate frequency platform wants to +switch to, and target_intermediate() should set CPU to to that frequency, before +jumping to the frequency corresponding to 'index'. Core will take care of +sending notifications and driver doesn't have to handle them in +target_intermediate() or target_index().
Is it worth documenting that if we implement target_intermediate() that target_index() must not fail? That means that any failure-prone things (like setting a regulator) should happen in target_index().
- Frequency Table Helpers
diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c index 9bf12a2..f38f2f2 100644 --- a/drivers/cpufreq/cpufreq.c +++ b/drivers/cpufreq/cpufreq.c @@ -1819,27 +1819,50 @@ EXPORT_SYMBOL(cpufreq_unregister_notifier); static int __target_index(struct cpufreq_policy *policy, struct cpufreq_frequency_table *freq_table, int index) {
struct cpufreq_freqs freqs;
struct cpufreq_freqs freqs = {.old = policy->cur, .flags = 0}; int retval = -EINVAL; bool notify; notify = !(cpufreq_driver->flags & CPUFREQ_ASYNC_NOTIFICATION);if (!notify)goto skip_notify;
I'm personally not a fan of using goto here. All you're trying to do is avoiding a level of indentation? If it really matters that much then create a sub function. IMHO goto should generally be reserved for error handling.
if (notify) {freqs.old = policy->cur;freqs.new = freq_table[index].frequency;freqs.flags = 0;
/* Handle switching to intermediate frequency */if (cpufreq_driver->get_intermediate) {freqs.new = cpufreq_driver->get_intermediate(policy, index);
Would it be worth it to change this to?
intermediate = 0 if (cpufreq_driver->get_intermediate) intermediate = cpufreq_driver->get_intermediate(); if (intermediate)
...the idea being that a driver may use an intermediate frequency for some transitions but not for all. For instance: on tegra if you happen to change to the exact clock frequency of the intermediate PLL it just stays there. There's no need for two notifications in that case. There may be other systems that can optimize some transitions to totally skip the intermediate stage (maybe you've got an non-glitching divider somewhere so you can optimize a transition from 1.4GHz to 700MHz to go w/ no intermediate jump).
pr_debug("%s: cpu: %d, oldfreq: %u, new freq: %u\n",
pr_debug("%s: cpu: %d, switching to intermediate freq: oldfreq: %u, intermediate freq: %u\n", __func__, policy->cpu, freqs.old, freqs.new); cpufreq_freq_transition_begin(policy, &freqs);retval = cpufreq_driver->target_intermediate(policy, freqs.new);
It feels like you want to pass in "index" here too, just in case. A driver may need to make decisions about other clocks based on the eventual final frequency. They could cache it themselves from the get_intermediate() call, but that seems ugly.
@@ -2361,7 +2384,8 @@ int cpufreq_register_driver(struct cpufreq_driver *driver_data) !(driver_data->setpolicy || driver_data->target_index || driver_data->target) || (driver_data->setpolicy && (driver_data->target_index ||
driver_data->target)))
driver_data->target)) ||(!!driver_data->get_intermediate ^ !!driver_data->target_intermediate))
I'm OK with the !! trick, but using ^ here seems more confusing. Why not use "!="? (!!driver_data->get_intermediate != !!driver_data->target_intermediate))
-Doug