linux-kernel - RE: [PATCH v4 3/3] eeprom: at24: enable runtime pm support

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Date:   Fri, 1 Sep 2017 18:26:47 +0000
From:   "Mohandass, Divagar" <divagar.mohandass@...el.com>
To:     Sakari Ailus <sakari.ailus@....fi>
CC:     "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "wsa@...-dreams.de" <wsa@...-dreams.de>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Mani, Rajmohan" <rajmohan.mani@...el.com>
Subject: RE: [PATCH v4 3/3] eeprom: at24: enable runtime pm support

Hi Sakari,

Thanks for the review.
My comments below.

---
^Divagar

>-----Original Message-----
>From: Sakari Ailus [mailto:sakari.ailus@....fi]
>Sent: Thursday, August 31, 2017 9:07 PM
>To: Mohandass, Divagar <divagar.mohandass@...el.com>
>Cc: robh+dt@...nel.org; mark.rutland@....com; wsa@...-dreams.de;
>devicetree@...r.kernel.org; linux-i2c@...r.kernel.org; linux-
>kernel@...r.kernel.org; Mani, Rajmohan <rajmohan.mani@...el.com>
>Subject: Re: [PATCH v4 3/3] eeprom: at24: enable runtime pm support
>
>On Thu, Aug 31, 2017 at 11:24:38AM +0000, Mohandass, Divagar wrote:
>> >> @@ -743,6 +770,14 @@ static int at24_probe(struct i2c_client
>> >> *client, const struct i2c_device_id *id)
>> >>
>> >>  	i2c_set_clientdata(client, at24);
>> >>
>> >> +	/* enable runtime pm */
>> >> +	pm_runtime_get_noresume(&client->dev);
>> >> +	err = pm_runtime_set_active(&client->dev);
>> >> +	if (err < 0)
>> >> +		goto err_clients;
>> >
>> >Btw. I don't think pm_runtime_set_active() can fail here. In other
>> >words it'd be fine to ignore the return value.
>> >
>>
>> Ack
>>
>>
>> >> +
>> >> +	pm_runtime_enable(&client->dev);
>> >> +
>> >>  	/*
>> >>  	 * Perform a one-byte test read to verify that the
>> >>  	 * chip is functional.
>> >> @@ -753,6 +788,8 @@ static int at24_probe(struct i2c_client
>> >> *client, const
>> >struct i2c_device_id *id)
>> >>  		goto err_clients;
>> >
>> >I suppose the runtime PM state is re-initialised for a device when a
>> >driver is probed, but it'd still be nice to decrement the use count if this
>fails.
>>
>> Ack
>>
>> >You should also disable PM runtime if probe fails and set the device
>> >suspended again.
>> >
>> >Same for other error cases. I think you'll need a new label.
>> >
>>
>> Can I disable PM runtime and set suspend in the 'err_clients' label itself ?
>
>Disable, yes, but the get and put calls need to be balanced.

We are performing pm_runtime_put after the first read check and in the error condition, so PM runtime disable alone should be sufficient in the 'err_clients' label.
I think it is balanced, your comments ?

>
>--
>Sakari Ailus
>e-mail: sakari.ailus@....fi