>On Mon 23 Apr 19:48 PDT 2018, Chanwoo Choi wrote:
>
>> Hi,
>>
>> On 2018??? 04??? 24??? 09:20, Bjorn Andersson wrote:
>> > The code in devfreq_add_device() handles the case where a freq_table is
>> > passed by the client, but then requests min and max frequences from
>> > the, in this case absent, opp tables.
>> >
>> > Read the min and max frequencies from the frequency table, which has
>> > been built from the opp table if one exists, instead of querying the
>> > opp table.
>> >
>> > Signed-off-by: Bjorn Andersson <bjorn.andersson@xxxxxxxxxx>
>> > ---
>> >
>> > An alternative approach is to clarify in the devfreq code that it's not
>> > possible to pass a freq_table and then in patch 3 create an opp table for the
>> > device in runtime; although the error handling of this becomes non-trivial.
>> >
>> > Transitioning the UFSHCD to use opp tables directly is hindered by the fact
>> > that the Qualcomm UFS hardware has two different clocks that needs to be
>> > running at different rates, so we would need a way to describe the two rates in
>> > the opp table. (And would force us to change the DT binding)
>> >
>> > drivers/devfreq/devfreq.c | 22 ++++------------------
>> > 1 file changed, 4 insertions(+), 18 deletions(-)
>> >
>> > diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
>> > index fe2af6aa88fc..086ced50a13d 100644
>> > --- a/drivers/devfreq/devfreq.c
>> > +++ b/drivers/devfreq/devfreq.c
>> > @@ -74,30 +74,16 @@ static struct devfreq *find_device_devfreq(struct device *dev)
>> >
>> > static unsigned long find_available_min_freq(struct devfreq *devfreq)
>> > {
>> > - struct dev_pm_opp *opp;
>> > - unsigned long min_freq = 0;
>> > -
>> > - opp = dev_pm_opp_find_freq_ceil(devfreq->dev.parent, &min_freq);
>> > - if (IS_ERR(opp))
>> > - min_freq = 0;
>> > - else
>> > - dev_pm_opp_put(opp);
>> > + struct devfreq_dev_profile *profile = devfreq->profile;
>> >
>> > - return min_freq;
>> > + return profile->freq_table[0];
>>
>> It is wrong. The thermal framework support the devfreq-cooling device
>> which uses the dev_pm_opp_enable/disable().
>>
>
>Okay, that makes sense. So rather than registering a custom freq_table I
>should register the min and max frequency using dev_pm_opp_add().
>
>> In order to find the correct available min frequency,
>> the devfreq have to use the OPP function instead of using the first entry
>> of the freq_table array.
>>
>
>Based on this there seems to be room for cleaning out the freq_table
>from devfreq, to reduce the confusion. I will review this further.
Could you please check if the bug suffering you gets resolved by
replacing 0 with ULONG_MAX in the function find_available_max_freq?
- max_freq = 0;
+ max_freq = ULONG_MAX;
Even if you are not using OPP, these functions should provide somewhat
"compatible" values.
Cheers,
MyungJoo
>
>Thanks,
>Bjorn
>
