linux-kernel - Re: [PATCH v3 04/11] i2c: riic: Enable runtime PM autosuspend support

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Message-ID: <b5dd19d3-9a08-4187-b976-c197a2c0d9d7@tuxon.dev>
Date: Fri, 12 Jul 2024 10:49:07 +0300
From: claudiu beznea <claudiu.beznea@...on.dev>
To: Biju Das <biju.das.jz@...renesas.com>,
 Chris Brandt <Chris.Brandt@...esas.com>,
 "andi.shyti@...nel.org" <andi.shyti@...nel.org>,
 "robh@...nel.org" <robh@...nel.org>, "krzk+dt@...nel.org"
 <krzk+dt@...nel.org>, "conor+dt@...nel.org" <conor+dt@...nel.org>,
 "geert+renesas@...der.be" <geert+renesas@...der.be>,
 "magnus.damm@...il.com" <magnus.damm@...il.com>,
 "p.zabel@...gutronix.de" <p.zabel@...gutronix.de>,
 "wsa+renesas@...g-engineering.com" <wsa+renesas@...g-engineering.com>
Cc: "linux-renesas-soc@...r.kernel.org" <linux-renesas-soc@...r.kernel.org>,
 "linux-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>,
 "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
 "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
 Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
Subject: Re: [PATCH v3 04/11] i2c: riic: Enable runtime PM autosuspend support



On 12.07.2024 10:45, Biju Das wrote:
> Hi Claudiu,
> 
>> -----Original Message-----
>> From: claudiu beznea <claudiu.beznea@...on.dev>
>> Sent: Friday, July 12, 2024 8:41 AM
>> Subject: Re: [PATCH v3 04/11] i2c: riic: Enable runtime PM autosuspend support
>>
>> Hi, Biju,
>>
>> On 12.07.2024 10:15, Biju Das wrote:
>>> Hi Claudiu,
>>>
>>>> -----Original Message-----
>>>> From: Claudiu <claudiu.beznea@...on.dev>
>>>> Sent: Thursday, July 11, 2024 12:52 PM
>>>> Subject: [PATCH v3 04/11] i2c: riic: Enable runtime PM autosuspend
>>>> support
>>>>
>>>> From: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
>>>>
>>>> Enable runtime PM autosuspend support for the RIIC driver. With this,
>>>> in case there are consecutive xfer requests the device wouldn't be
>>>> runtime enabled/disabled after each consecutive xfer but after the
>>>> the delay configured by user. With this, we can avoid touching
>>>> hardware registers involved in runtime PM suspend/resume saving in this way some cycles. The
>> default chosen autosuspend delay is zero to keep the previous driver behavior.
>>>
>>> On the other hand, you are saving power. Currently the driver is
>>> highly optimized for Power usage.
>>>
>>> Before transfer turn on the clock
>>> After transfer turn off the clock, this is the optimal power usage correspond to suspend delay.
>>>
>>> By adding suspend delay, you are consuming power corresponding to that
>>> delay.
>>
>> The default delay is zero, see the following diff in this patch:
>>
>> @@ -479,6 +481,8 @@ static int riic_i2c_probe(struct platform_device *pdev)
>>
>>  	i2c_parse_fw_timings(dev, &i2c_t, true);
>>
>> +	pm_runtime_set_autosuspend_delay(dev, 0);
> 
> I just provided justification, why you addes 0  msec here, compared to xx msec
> in the original internal version.

Isn't it in the commit description already?

"The default chosen autosuspend delay is zero to keep the
previous driver behavior."

> 
> Cheers,
> Biju