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Message-ID: <CACRpkdarYo06heRhhi0o5bKbMnVveQ+2j+oKHokxCNftCzq_cg@mail.gmail.com>
Date: Fri, 11 Feb 2022 02:12:22 +0100
From: Linus Walleij <linus.walleij@...aro.org>
To: Jonathan Cameron <Jonathan.Cameron@...wei.com>
Cc: Massimo Toscanelli <massimo.toscanelli@...ca-geosystems.com>,
linux-kernel@...r.kernel.org, jic23@...nel.org, lars@...afoo.de,
caihuoqing@...du.com, aardelean@...iqon.com,
andy.shevchenko@...il.com, hdegoede@...hat.com,
Qing-wu.Li@...ca-geosystems.com.cn, stephan@...hold.net,
linux-iio@...r.kernel.org, bsp-development.geo@...ca-geosystems.com
Subject: Re: [PATCH RESEND 0/2] Solve data access delay of ST sensors
On Mon, Feb 7, 2022 at 2:59 PM Jonathan Cameron
<Jonathan.Cameron@...wei.com> wrote:
> On Mon, 7 Feb 2022 09:04:41 +0000
> Massimo Toscanelli <massimo.toscanelli@...ca-geosystems.com> wrote:
> The standard approach to avoiding rapid power up and power down cycles
> is to use runtime_pm with autosuspend and a period set at a period
> of perhaps 1 second. Would that work for you? You'll pay the costs
> of power up only on the first read after a period of not reading.
>
> Exposing the control to userspace for this sort of thing is normally
> a bad idea because userspace generally has no idea if it should use it
> as there is no clean way of telling userspace the costs of not using
> it (as those will be device specific).
>
> If you have a usecase that requires regular reading you should also
> think about whether using the buffered interface is more appropriate.
> IIRC that will keep these devices powered up continuously whilst
> the buffer is enabled and will provide a lower overhead way of
> reading data than sysfs reads.
I see that I have repeted similar comments.
Sorry for the hammering.
I agree with Jonathan's stance here.
Yours,
Linus Walleij
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