On Mon, Dec 15, 2014 at 9:10 PM, Viresh Kumar <viresh.ku...@linaro.org> wrote:
> On 16 December 2014 at 05:40, Dmitry Torokhov <d...@chromium.org> wrote:
>> cpufreq-dt driver supports mode when OPP table is provided by platform
>> code and not device tree. However on certain platforms code that fills
>> OPP table may run after cpufreq driver tries to initialize, so let's
>> report -EPROBE_DEFER if we do not find any entires in OPP table for the
>> CPU.
>>
>> Signed-off-by: Dmitry Torokhov <d...@chromium.org>
>> ---
>> drivers/cpufreq/cpufreq-dt.c | 13 +++++++++++++
>> 1 file changed, 13 insertions(+)
>>
>> diff --git a/drivers/cpufreq/cpufreq-dt.c b/drivers/cpufreq/cpufreq-dt.c
>> index f56147a..4f874fa 100644
>> --- a/drivers/cpufreq/cpufreq-dt.c
>> +++ b/drivers/cpufreq/cpufreq-dt.c
>> @@ -211,6 +211,19 @@ static int cpufreq_init(struct cpufreq_policy *policy)
>> /* OPPs might be populated at runtime, don't check for error here */
>> of_init_opp_table(cpu_dev);
>>
>> + /*
>> + * But we need OPP table to function so if it is not there let's
>> + * give platform code chance to provide it for us.
>> + */
>> + rcu_read_lock();
>> + ret = dev_pm_opp_get_opp_count(cpu_dev);
>> + rcu_read_unlock();
>> + if (ret <= 0) {
>> + pr_debug("OPP table is not ready, deferring probe\n");
>> + ret = -EPROBE_DEFER;
>> + goto out_free_opp;
>
> Hmm, so we are trying to free opps while we failed to find one.
>
> Are you sure you have tested this on one such platform where we
> fail here?
Not with the linux-next, but generally yes.
>
> Because this is what I see:
>
> void of_free_opp_table(struct device *dev)
> {
> struct device_opp *dev_opp;
> struct dev_pm_opp *opp, *tmp;
>
> /* Check for existing list for 'dev' */
> dev_opp = find_device_opp(dev);
> if (WARN(IS_ERR(dev_opp), "%s: dev_opp: %ld\n", dev_name(dev),
> PTR_ERR(dev_opp)))
> return;
>
> ...
> }
>
>
> And we probably will hit this WARN(), wouldn't we ?
Yes we will. Which simply means that this WARN is stupid. We also will
hit it if there is no opp table and the allocation below fails; or if
it succeeds then dev_pm_opp_init_cpufreq_table() will fail and we'll
hit this code path again.
We should either drop that WARN() or handle -ENODEV there properly.
Thanks,
Dmitry
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