linux-kernel - Re: [PATCH 5/5] i2c: imx-lpi2c: increase PM timeout to avoid operate clk frequently

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Message-ID: <3775392.MHq7AAxBmi@steina-w>
Date: Fri, 30 Aug 2024 11:07:10 +0200
From: Alexander Stein <alexander.stein@...tq-group.com>
To: Aisheng Dong <aisheng.dong@....com>, "andi.shyti@...nel.org" <andi.shyti@...nel.org>, "shawnguo@...nel.org" <shawnguo@...nel.org>, "s.hauer@...gutronix.de" <s.hauer@...gutronix.de>, "kernel@...gutronix.de" <kernel@...gutronix.de>, "festevam@...il.com" <festevam@...il.com>, "linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org>, Carlos Song <carlos.song@....com>
Cc: "linux-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>, "imx@...ts.linux.dev" <imx@...ts.linux.dev>, "linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 5/5] i2c: imx-lpi2c: increase PM timeout to avoid operate clk frequently

Hi,

Am Freitag, 30. August 2024, 10:53:16 CEST schrieb Carlos Song:
> > -----Original Message-----
> > From: Alexander Stein <alexander.stein@...tq-group.com>
> > Sent: Thursday, August 29, 2024 6:55 PM
> > To: Aisheng Dong <aisheng.dong@....com>; andi.shyti@...nel.org;
> > shawnguo@...nel.org; s.hauer@...gutronix.de; kernel@...gutronix.de;
> > festevam@...il.com; linux-arm-kernel@...ts.infradead.org
> > Cc: linux-i2c@...r.kernel.org; imx@...ts.linux.dev;
> > linux-arm-kernel@...ts.infradead.org; linux-kernel@...r.kernel.org; Carlos Song
> > <carlos.song@....com>
> > Subject: [EXT] Re: [PATCH 5/5] i2c: imx-lpi2c: increase PM timeout to avoid
> > operate clk frequently
> >
> > Caution: This is an external email. Please take care when clicking links or
> > opening attachments. When in doubt, report the message using the 'Report this
> > email' button
> >
> >
> > Hi,
> >
> > Am Donnerstag, 29. August 2024, 11:37:22 CEST schrieb carlos.song@....com:
> > > From: Clark Wang <xiaoning.wang@....com>
> > >
> > > Switching the clock frequently will affect the data transmission
> > > efficiency, and prolong the timeout to reduce autosuspend times for
> > > lpi2c.
> >
> > Efficiency as in throughput or total time per transfer? Do you have any numbers?
> >
> 
> Hi, Thank your for your quick ack!
> 
> Apologies for the unclear explanation. The efficiency I'm referring to isn't just for I2C. For platforms with SC firmware
> like the 8X series, every i2c transfer to enable or disable the clock notifies the SC firmware to perform a clock operation.
> So if the autosuspend time is short, i2c may enable and disable clock frequently, it will occupy resources of the SC firmware.
> 
> Therefore, we add this patch to minimize the excessive sc firmware resource waste caused by frequent I2C clock enable/disable operations.

Thanks for the explanation. So this delay only occurs on systems using an SC (imx8qm/qxp) or SM (imx95), right?
Is there a chance to detect this kind of clock provider and make this timeout configurable?

Best regards,
Alexander
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