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cpufreq: Make sure CPU is running on a freq from freq-table

Message ID 528F01C4.1050608@linaro.org
State New
Headers show

Commit Message

Viresh Kumar Nov. 22, 2013, 7:03 a.m. UTC 
On Thursday 21 November 2013 12:39 PM, Viresh Kumar wrote:
> Sometimes boot loaders set CPU frequency to a value outside of frequency table
> present with cpufreq core. In such cases CPU might be unstable if it has to run
> on that frequency for long duration of time and so its better to set it to a
> frequency which is specified in freq-table. This also makes cpufreq stats
> inconsistent as cpufreq-stats would fail to register because current frequency
> of CPU isn't found in freq-table.
> 
> Because we don't want this change to effect boot process badly, we go for the
> next freq which is >= policy->cur ('cur' must be set by now, otherwise we will
> end up setting freq to lowest of the table as 'cur' is initialized to zero).
> 
> In case where CPU is already running on one of the frequencies present in
> freq-table, this would turn into a dummy call as __cpufreq_driver_target() would
> return early.
> 
> Reported-by: Carlos Hernandez <ceh@ti.com>
> Reported-by: Nishanth Menon <nm@ti.com>
> Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>

Copying another mail from Nishant here to get my cc'list back..

On Friday 22 November 2013 05:12 AM, Nishanth Menon wrote:
> I gave this a quick run on my 3.12 kernel:
> http://pastebin.mozilla.org/3649730 is what I applied and output
> http://pastebin.mozilla.org/3649729
>
> I need to see what I might have mucked up.. or see if I can test this
> on 3.13 master on a different board (since OMAP5 wont boot in master
> without clock dts nodes :()..

This happened because of common sense, which was missing in my patch :)

Try this over existing patch:

        /* related cpus should atleast have policy->cpus */

Comments

Nishanth Menon Nov. 22, 2013, 9:43 p.m. UTC | #1 
On 11/22/2013 01:03 AM, viresh kumar wrote:
> On Thursday 21 November 2013 12:39 PM, Viresh Kumar wrote:

[...]
> Copying another mail from Nishant here to get my cc'list back..
> 
> On Friday 22 November 2013 05:12 AM, Nishanth Menon wrote:
>> I gave this a quick run on my 3.12 kernel:
>> http://pastebin.mozilla.org/3649730 is what I applied and output
>> http://pastebin.mozilla.org/3649729
>>
>> I need to see what I might have mucked up.. or see if I can test this
>> on 3.13 master on a different board (since OMAP5 wont boot in master
>> without clock dts nodes :()..
> 
> This happened because of common sense, which was missing in my patch :)
> 
> Try this over existing patch:


Works like a charm :) thanks.

http://pastebin.mozilla.org/3655494 -> simple Ondemand governor testing.
http://pastebin.mozilla.org/3655493 -> simple Userspace governor testing.

> 
> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> index 6e8b226..e403388 100644
> --- a/drivers/cpufreq/cpufreq.c
> +++ b/drivers/cpufreq/cpufreq.c
> @@ -1126,13 +1126,19 @@ static int __cpufreq_add_dev(struct device *dev, struct
> subsys_interface *sif,
>          * In case where CPU is already running on one of the frequencies
>          * present in freq-table, this would turn into a dummy call as
>          * __cpufreq_driver_target() would return early.
> +        *
> +        * We are passing target-freq as "policy->cur - 1" otherwise
> +        * __cpufreq_driver_target() would simply fail, as policy->cur will be
> +        * equal to target-freq.
>          */
>         if (has_target()) {
> -               ret = __cpufreq_driver_target(policy, policy->cur,
> +               ret = __cpufreq_driver_target(policy, policy->cur - 1,
>                                 CPUFREQ_RELATION_L);
> -               if (ret)
> +               if (ret) {
>                         pr_err("%s: Unable to set frequency from table: %d\n",
>                                         __func__, ret);
> +                       goto err_out_unregister;
> +               }
>         }
> 
>         /* related cpus should atleast have policy->cpus */
>
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Patch

diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index 6e8b226..e403388 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -1126,13 +1126,19 @@  static int __cpufreq_add_dev(struct device *dev, struct
subsys_interface *sif,
         * In case where CPU is already running on one of the frequencies
         * present in freq-table, this would turn into a dummy call as
         * __cpufreq_driver_target() would return early.
+        *
+        * We are passing target-freq as "policy->cur - 1" otherwise
+        * __cpufreq_driver_target() would simply fail, as policy->cur will be
+        * equal to target-freq.
         */
        if (has_target()) {
-               ret = __cpufreq_driver_target(policy, policy->cur,
+               ret = __cpufreq_driver_target(policy, policy->cur - 1,
                                CPUFREQ_RELATION_L);
-               if (ret)
+               if (ret) {
                        pr_err("%s: Unable to set frequency from table: %d\n",
                                        __func__, ret);
+                       goto err_out_unregister;
+               }
        }