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

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Message-ID:
 <TY3PR01MB1134611DB941585B340D09B7186A62@TY3PR01MB11346.jpnprd01.prod.outlook.com>
Date: Fri, 12 Jul 2024 07:45:10 +0000
From: Biju Das <biju.das.jz@...renesas.com>
To: Claudiu.Beznea <claudiu.beznea@...on.dev>, 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

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.

Cheers,
Biju