linux-kernel - Re: [RESEND v6,2/3] i2c: mux: pca954x: support property idle-state

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Date:   Fri, 3 Jan 2020 14:06:14 +0000
From:   Peter Rosin <peda@...ntia.se>
To:     Biwen Li <biwen.li@....com>,
        "leoyang.li@....com" <leoyang.li@....com>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "mark.rutland@....com" <mark.rutland@....com>
CC:     "linux-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>
Subject: Re: [RESEND v6,2/3] i2c: mux: pca954x: support property idle-state

On 2019-12-25 11:36, Biwen Li wrote:
> This supports property idle-state,if present,
> overrides i2c-mux-idle-disconnect.
> 
> My use cases:
> 	- Use the property idle-state to fix
> 	  an errata on LS2085ARDB and LS2088ARDB.
> 	- Errata id: E-00013(board LS2085ARDB and
> 	  LS2088ARDB revision on Rev.B, Rev.C and Rev.D).
> 	- About E-00013:
> 	  - Description: I2C1 and I2C3 buses
> 	    are missing pull-up.
> 	  - Impact: When the PCA954x device is tri-stated, the I2C bus
> 	    will float. This makes the I2C bus and its associated
> 	    downstream devices inaccessible.
> 	  - Hardware fix: Populate resistors R189 and R190 for I2C1
> 	    and resistors R228 and R229 for I2C3.
> 	  - Software fix: Remove the tri-state option from the PCA954x
> 	    driver(PCA954x always on enable status, specify a
> 	    channel zero in dts to fix the errata E-00013).
> 
> Tested-by: Ioana Ciornei <ioana.ciornei@....com>
> Signed-off-by: Biwen Li <biwen.li@....com>

Pushed to i2c-mux/for-next with some minor language tweaks.

Cheers,
Peter