linux-kernel - Re: [PATCH v1] opp: Release current OPP properly

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Date:   Fri, 13 Aug 2021 20:23:10 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Viresh Kumar <viresh.kumar@...aro.org>
Cc:     Viresh Kumar <vireshk@...nel.org>, Stephen Boyd <sboyd@...nel.org>,
        Nishanth Menon <nm@...com>, linux-kernel@...r.kernel.org,
        linux-pm@...r.kernel.org
Subject: Re: [PATCH v1] opp: Release current OPP properly

13.08.2021 07:12, Viresh Kumar пишет:
> On 12-08-21, 13:13, Dmitry Osipenko wrote:
>> The current_opp is released only when whole OPP table is released,
>> otherwise it's only marked as removed by dev_pm_opp_remove_table().
>> Functions like dev_pm_opp_put_clkname() and dev_pm_opp_put_supported_hw()
>> are checking whether OPP table is empty and it's not if current_opp is
>> set since it holds the refcount of OPP, this produces a noisy warning
>> from these functions about busy OPP table. Release current_opp when
>> OPP table is removed to fix it.
>>
>> Cc: stable@...r.kernel.org
>> Fixes: 81c4d8a3c414 ("opp: Keep track of currently programmed OPP")
>> Signed-off-by: Dmitry Osipenko <digetx@...il.com>
>> ---
>>  drivers/opp/core.c | 9 ++++++---
>>  1 file changed, 6 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/opp/core.c b/drivers/opp/core.c
>> index b335c077f215..73da968b5c86 100644
>> --- a/drivers/opp/core.c
>> +++ b/drivers/opp/core.c
>> @@ -1378,9 +1378,6 @@ static void _opp_table_kref_release(struct kref *kref)
>>  	list_del(&opp_table->node);
>>  	mutex_unlock(&opp_table_lock);
>>  
>> -	if (opp_table->current_opp)
>> -		dev_pm_opp_put(opp_table->current_opp);
>> -
>>  	_of_clear_opp_table(opp_table);
>>  
>>  	/* Release clk */
>> @@ -2901,6 +2898,12 @@ void dev_pm_opp_remove_table(struct device *dev)
>>  	if (_opp_remove_all_static(opp_table))
>>  		dev_pm_opp_put_opp_table(opp_table);
>>  
>> +	/* Drop reference taken by _find_current_opp() */
>> +	if (opp_table->current_opp) {
>> +		dev_pm_opp_put(opp_table->current_opp);
>> +		opp_table->current_opp = NULL;
>> +	}
>> +
> 
> It is better to drop the reference when the OPP table is really
> getting removed.
> 
> I think the WARN_ON() in the put_* functions can be dropped. It is
> important to check this when the stuff is getting set, like in
> dev_pm_opp_set_supported_hw(), but removal is just fine.
> 

Alright, I'll make another patch then.