linux-kernel - RE: [EXT] Re: [PATCH] i2c: pca954x: Add property to skip disabling PCA954x MUX device

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Message-ID: <DB7PR04MB449059DCF1A24CFBBFEAFF678F820@DB7PR04MB4490.eurprd04.prod.outlook.com>
Date:   Mon, 30 Sep 2019 02:48:04 +0000
From:   Biwen Li <biwen.li@....com>
To:     "cengiz@...nel.wtf" <cengiz@...nel.wtf>
CC:     "linux-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "peda@...ntia.se" <peda@...ntia.se>, Leo Li <leoyang.li@....com>,
        Wolfram Sang <wsa@...-dreams.de>
Subject: RE: [EXT] Re: [PATCH] i2c: pca954x: Add property to skip disabling
 PCA954x MUX device

> 
> Hello Biwen,
> 
> > +       /* Errata ID E-00013 on board LS2088ARDB and LS2088ARDB:
> > +        * The point here is that you must not disable a mux if there
> > +        * are no pullups on the input or you mess up the I2C. This
> > +        * needs to be put into the DTS really as the kernel cannot
> > +        * know this otherwise.
> > +        */
> 
> Can you please explain what a "mess up" is?
This is a hardware bug that happened on NXP board LS2085ARDB and LS2088ARDB.
So give a software fix for the hardware bug.
> 
> And also, should we put this new DTS property in related default bindings?
> 
> If not, are you planning a documentation update for the users to notify them
> about this?
I will update bindings document on v2.
> 
> --
> Cengiz Can <cengiz@...nel.wtf>