linux-kernel - Re: Errant readings on LM81 with T2080 SoC

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Message-ID: <61f68c59-593b-e393-5520-d9acc14fdf97@alliedtelesis.co.nz>
Date:   Mon, 8 Mar 2021 22:10:04 +0000
From:   Chris Packham <Chris.Packham@...iedtelesis.co.nz>
To:     Guenter Roeck <linux@...ck-us.net>,
        "jdelvare@...e.com" <jdelvare@...e.com>
CC:     "linux-hwmon@...r.kernel.org" <linux-hwmon@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>,
        "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>
Subject: Re: Errant readings on LM81 with T2080 SoC


On 8/03/21 5:59 pm, Guenter Roeck wrote:
> On 3/7/21 8:37 PM, Chris Packham wrote:
> [ ... ]
>>> That's from -ENXIO which is used in only one place in i2c-mpc.c. I'll
>>> enable some debug and see what we get.
>> For the errant readings there was nothing abnormal reported by the driver.
>>
>> For the "No such device or address" I saw "mpc-i2c ffe119000.i2c: No
>> RXAK" which matches up with the -ENXIO return.
>>
> Id suggest to check the time until not busy and stop in mpc_xfer().
> Those hot loops are unusual, and may well mess up the code especially
> if preempt is enabled.
Reworking those loops seems to have had a positive result. I'll do a bit 
more testing and hopefully get a patch out later today.
>   Also, are you using interrupts or polling in
> your system ? The interrupt handler looks a bit odd, with "Read again
> to allow register to stabilise".
>
> Do you have fsl,timeout set in the devicetree properties and, if so,
> have you played with it ?
>
> Other than that, the only other real idea I have would be to monitor
> the i2c bus.
>
> Guenter