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From: Linus Walleij <linus.walleij@linaro.org>
To: Jonathan Cameron <jic23@kernel.org>
Cc: "Mike Looijmans" <mike.looijmans@topic.nl>,
	linux-iio <linux-iio@vger.kernel.org>,
	"Dan Robertson" <dan@dlrobertson.com>,
	"Gaëtan André" <rvlander@gaetanandre.eu>,
	"Jonathan Bakker" <xc-racer2@live.ca>,
	"Lars-Peter Clausen" <lars@metafoo.de>,
	"Peter Meerwald-Stadler" <pmeerw@pmeerw.net>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v6 2/2] iio: accel: Add support for the Bosch-Sensortec BMI088
Date: Sun, 24 Jan 2021 00:21:13 +0100	[thread overview]
Message-ID: <CACRpkdZTJbAFK0j8U84pyW6za-SGJqGWnvertj8sXxc8Ou8VeA@mail.gmail.com> (raw)
In-Reply-To: <20210123153511.1802a15a@archlinux>

On Sat, Jan 23, 2021 at 4:35 PM Jonathan Cameron <jic23@kernel.org> wrote:
> [Me]
> > Next, I think it is better to let suspend/resume, i.e. system PM
> > reuse runtime PM since you're implementing that. This is why
> > we invented PM runtime force resume and force suspend.
>
> Here the driver is turning more off for full suspend than in the
> runtime path.  If that results in significant extra delay then
> it's not appropriate to have that in the runtime suspend path.

I see the point.

The resume path calls bmi088_accel_enable() which incurs
a 5ms delay.

The runtime resume path incurs a 1 ms delay.

The runtime autosuspend kicks in after 2 ms.

> Maybe the simplification of not doing the deeper power saving
> mode is worth the extra power cost or extra delay, but
> I'm not yet convinced.

I would personally set the autosuspend to ~20ms and just use
one path and take a hit of 5 ms whenever we go down between
measures if it is a system that is for human interaction, but for
control systems this more complex set-up may be better for
response latencies.

The current approach may be better tuned to perfection and
we are all perfectionists :D

I'm just worrying a little about bugs and maintainability.

Yours,
Linus Walleij

  reply	other threads:[~2021-01-23 23:22 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-01-19 12:46 [PATCH v6 1/2] dt-bindings: iio: accel: Add bmi088 accelerometer bindings Mike Looijmans
2021-01-19 12:46 ` [PATCH v6 2/2] iio: accel: Add support for the Bosch-Sensortec BMI088 Mike Looijmans
2021-01-20 10:09   ` kernel test robot
2021-01-20 20:22   ` Jonathan Cameron
     [not found]     ` <1b153bce-a66a-45ee-a5c6-963ea6fb1c82.949ef384-8293-46b8-903f-40a477c056ae.c4ec3c42-7acb-4ce8-997f-adf405d31335@emailsignatures365.codetwo.com>
     [not found]       ` <1b153bce-a66a-45ee-a5c6-963ea6fb1c82.0d2bd5fa-15cc-4b27-b94e-83614f9e5b38.ca49b241-105e-4dde-a295-e8168cb6d390@emailsignatures365.codetwo.com>
2021-01-21  9:02         ` Mike Looijmans
2021-01-22 22:38   ` Linus Walleij
2021-01-23 15:35     ` Jonathan Cameron
2021-01-23 23:21       ` Linus Walleij [this message]
2021-01-24 13:23         ` Jonathan Cameron
     [not found]           ` <1b153bce-a66a-45ee-a5c6-963ea6fb1c82.949ef384-8293-46b8-903f-40a477c056ae.e23f1b65-3084-4bd7-abd5-c186f8c4c35c@emailsignatures365.codetwo.com>
     [not found]             ` <1b153bce-a66a-45ee-a5c6-963ea6fb1c82.0d2bd5fa-15cc-4b27-b94e-83614f9e5b38.4d211e5c-af1f-4f0a-9714-ec208ef9be8d@emailsignatures365.codetwo.com>
2021-01-25  7:59               ` Mike Looijmans
2021-01-19 23:28 ` [PATCH v6 1/2] dt-bindings: iio: accel: Add bmi088 accelerometer bindings Rob Herring
2021-01-20  1:31 ` Rob Herring
     [not found]   ` <1b153bce-a66a-45ee-a5c6-963ea6fb1c82.949ef384-8293-46b8-903f-40a477c056ae.06120990-9bfb-4196-a6ce-19c5b16aae9a@emailsignatures365.codetwo.com>
     [not found]     ` <1b153bce-a66a-45ee-a5c6-963ea6fb1c82.0d2bd5fa-15cc-4b27-b94e-83614f9e5b38.70d7c9ca-f015-4fc4-8136-1c0364cd5511@emailsignatures365.codetwo.com>
2021-01-20  7:21       ` Mike Looijmans
2021-01-20 18:50 ` Jonathan Cameron
     [not found]   ` <1b153bce-a66a-45ee-a5c6-963ea6fb1c82.949ef384-8293-46b8-903f-40a477c056ae.c9179140-7138-467c-85e9-419e68c95bd4@emailsignatures365.codetwo.com>
     [not found]     ` <1b153bce-a66a-45ee-a5c6-963ea6fb1c82.0d2bd5fa-15cc-4b27-b94e-83614f9e5b38.02f2b6e0-f94c-4e13-b820-c0a2b10c9a96@emailsignatures365.codetwo.com>
2021-01-21  8:46       ` Mike Looijmans

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