Messages in this thread | | | Subject | Re: [PATCH v6 2/2] iio: accel: Add support for the Bosch-Sensortec BMI088 | From | Mike Looijmans <> | Date | Mon, 25 Jan 2021 08:59:43 +0100 |
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See below
Met vriendelijke groet / kind regards,
Mike Looijmans System Expert
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Please consider the environment before printing this e-mail On 24-01-2021 14:23, Jonathan Cameron wrote: > On Sun, 24 Jan 2021 00:21:13 +0100 > Linus Walleij <linus.walleij@linaro.org> wrote: > >> 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.
It's set to 2 seconds as I understand it. This to support reading a single value every second or so.
>> >>> 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. > Fully understood. Though for things like this I like to leave > it at the discretion of the driver author as fairly safe they > are a user of the device. > > May well make sense to go with the longer times as you > suggest though! Over to you Mike :)
I've been digging in the datasheet and it's really unclear how you're supposed to control the two power registers.
I think it's best to just put both control values into on/off state at the same time. I also prefer the simplicity of Linus' suggestion. I'll do some testing to see if the device behaves properly.
-- Mike Looijmans
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