linux-kernel - Re: [PATCH] i2c-mux-pca954x: Disable mux after 200ms timeout

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Message-ID: <529364AC.8000305@gmx.de>
Date:	Mon, 25 Nov 2013 15:54:36 +0100
From:	Michael Lawnick <ml.lawnick@....de>
To:	Mike Looijmans <mike.looijmans@...ic.nl>
CC:	Wolfram Sang <wsa@...-dreams.de>, linux-i2c@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] i2c-mux-pca954x: Disable mux after 200ms timeout

Hi,

Am 25.11.2013 14:43, schrieb Mike Looijmans:
> Leaving the mux enabled causes needless I2C traffic on the downstream
> bus. De-selecting after every request causes excess I2C traffic and
> switching.
>
> This patch implements a hybrid solution: After 200ms of inactivity,
> the mux is disabled.
...

Have you checked against behavior on cascaded muxes?
At least your desired timing will not look as expected.
200 ms: disable mux1
201 ms: enable mux1 - disable mux2
202 ms: enable mux2 - disable mux3
401 ms: disable mux1
402 ms: enable mux1 - disable mux2
602 ms: disable mux1
And on full second temperature sensor behind mux3 is read again ...

KR
Michael



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