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From: Leonard Crestez <leonard.crestez@nxp.com>
To: Matthias Kaehlcke <mka@chromium.org>,
	Viresh Kumar <viresh.kumar@linaro.org>
Cc: "Chanwoo Choi" <cw00.choi@samsung.com>,
	"MyungJoo Ham" <myungjoo.ham@samsung.com>,
	"Kyungmin Park" <kyungmin.park@samsung.com>,
	"Artur Świgoń" <a.swigon@partner.samsung.com>,
	"Saravana Kannan" <saravanak@google.com>,
	"Krzysztof Kozlowski" <krzk@kernel.org>,
	"Alexandre Bailon" <abailon@baylibre.com>,
	"Georgi Djakov" <georgi.djakov@linaro.org>,
	"Abel Vesa" <abel.vesa@nxp.com>, "Jacky Bai" <ping.bai@nxp.com>,
	"Lukasz Luba" <l.luba@partner.samsung.com>,
	dl-linux-imx <linux-imx@nxp.com>,
	"linux-pm@vger.kernel.org" <linux-pm@vger.kernel.org>,
	"linux-arm-kernel@lists.infradead.org"
	<linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH v9 2/8] PM / devfreq: Fix devfreq_notifier_call returning errno
Date: Wed, 2 Oct 2019 23:47:35 +0000
Message-ID: <VI1PR04MB7023EF602656CC360032E720EE9C0@VI1PR04MB7023.eurprd04.prod.outlook.com> (raw)
In-Reply-To: <20191002212437.GF87296@google.com>

On 2019-10-03 12:24 AM, Matthias Kaehlcke wrote:
> On Wed, Oct 02, 2019 at 10:25:05PM +0300, Leonard Crestez wrote:
>> Notifier callbacks shouldn't return negative errno but one of the
>> NOTIFY_OK/DONE/BAD values.
>>
>> The OPP core will ignore return values from notifiers but returning a
>> value that matches NOTIFY_STOP_MASK will stop the notification chain.
>>
>> Fix by always returning NOTIFY_OK.
>>
>> Signed-off-by: Leonard Crestez <leonard.crestez@nxp.com>
>> ---
>>   drivers/devfreq/devfreq.c | 24 +++++++++++++-----------
>>   1 file changed, 13 insertions(+), 11 deletions(-)
>>
>> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
>> index 7dc899da1172..32bbf6e80380 100644
>> --- a/drivers/devfreq/devfreq.c
>> +++ b/drivers/devfreq/devfreq.c
>> @@ -548,30 +548,32 @@ EXPORT_SYMBOL(devfreq_interval_update);
>>    */
>>   static int devfreq_notifier_call(struct notifier_block *nb, unsigned long type,
>>   				 void *devp)
>>   {
>>   	struct devfreq *devfreq = container_of(nb, struct devfreq, nb);
>> -	int ret;
>> +	int err = -EINVAL;
>>   
>>   	mutex_lock(&devfreq->lock);
>>   
>>   	devfreq->scaling_min_freq = find_available_min_freq(devfreq);
>> -	if (!devfreq->scaling_min_freq) {
>> -		mutex_unlock(&devfreq->lock);
>> -		return -EINVAL;
>> -	}
>> +	if (!devfreq->scaling_min_freq)
>> +		goto out;
>>   
>>   	devfreq->scaling_max_freq = find_available_max_freq(devfreq);
>> -	if (!devfreq->scaling_max_freq) {
>> -		mutex_unlock(&devfreq->lock);
>> -		return -EINVAL;
>> -	}
>> +	if (!devfreq->scaling_max_freq)
>> +		goto out;
>> +
>> +	err = update_devfreq(devfreq);
>>   
>> -	ret = update_devfreq(devfreq);
>> +out:
>>   	mutex_unlock(&devfreq->lock);
>> +	if (err)
>> +		dev_err(devfreq->dev.parent,
>> +			"failed to update frequency from OPP notifier (%d)\n",
>> +			err);
> 
> In case an OPP freq can't be found the log doesn't provide clues
> about what the problem could be. I couldn't find a clearly superior
> errno value though, so I guess this is as good as it gets, unless
> you want to have a dedicated message for those errors. Should be a
> rare exception anyway, and previously there was no log at all.

I guess it could happen if all OPPs are disabled after probe?

The devfreq core will attempt to switch away if the current OPP get 
disabled but if nothing else is available then printing an error and 
sticking to the current frequency seems reasonable.

It would indicate a bug somewhere else.

> Reviewed-by: Matthias Kaehlcke <mka@chromium.org>

  reply index

Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-02 19:25 [PATCH v9 0/8] PM / devfreq: Add dev_pm_qos support Leonard Crestez
2019-10-02 19:25 ` [PATCH v9 1/8] PM / devfreq: Don't fail devfreq_dev_release if not in list Leonard Crestez
2019-10-02 19:25 ` [PATCH v9 2/8] PM / devfreq: Fix devfreq_notifier_call returning errno Leonard Crestez
2019-10-02 21:24   ` Matthias Kaehlcke
2019-10-02 23:47     ` Leonard Crestez [this message]
2019-10-31  2:29   ` Chanwoo Choi
2019-10-02 19:25 ` [PATCH v9 3/8] PM / devfreq: Set scaling_max_freq to max on OPP notifier error Leonard Crestez
2019-10-02 21:33   ` Matthias Kaehlcke
2019-10-31  2:21   ` Chanwoo Choi
2019-10-02 19:25 ` [PATCH v9 4/8] PM / devfreq: Move more initialization before registration Leonard Crestez
2019-10-31  3:15   ` Chanwoo Choi
2019-10-31 13:31     ` Leonard Crestez
2019-11-01  8:31       ` Chanwoo Choi
2019-11-01 14:36         ` Leonard Crestez
2019-10-02 19:25 ` [PATCH v9 5/8] PM / devfreq: Don't take lock in devfreq_add_device Leonard Crestez
2019-10-02 19:25 ` [PATCH v9 6/8] PM / devfreq: Introduce get_freq_range helper Leonard Crestez
2019-10-03 18:19   ` Matthias Kaehlcke
2019-10-03 19:16     ` Leonard Crestez
2019-10-03 19:36       ` Matthias Kaehlcke
2019-10-11 18:29     ` Matthias Kaehlcke
2019-10-31  2:44       ` Chanwoo Choi
2019-10-31  2:42   ` Chanwoo Choi
2019-10-31 13:12     ` Leonard Crestez
2019-10-02 19:25 ` [PATCH v9 7/8] PM / devfreq: Add PM QoS support Leonard Crestez
2019-10-02 22:22   ` Matthias Kaehlcke
2019-10-04 17:04   ` Matthias Kaehlcke
2019-10-31  3:01   ` Chanwoo Choi
2019-10-31 13:21     ` Leonard Crestez
2019-10-02 19:25 ` [PATCH v9 8/8] PM / devfreq: Use PM QoS for sysfs min/max_freq Leonard Crestez
2019-10-04 17:05   ` Matthias Kaehlcke
2019-10-31  3:10   ` Chanwoo Choi
2019-10-23 14:06 ` [PATCH v9 0/8] PM / devfreq: Add dev_pm_qos support Leonard Crestez
2019-10-23 16:34   ` Matthias Kaehlcke
2019-10-24 16:21     ` Leonard Crestez

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