linux-kernel - Re: [PATCH v2] iio: adc: ti-ads7950: inconsistency with spi msg

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Date:   Fri, 25 Jan 2019 10:38:11 -0800
From:   Florian Fainelli <f.fainelli@...il.com>
To:     justinpopo6@...il.com, linux-iio@...r.kernel.org
Cc:     jic23@...nel.org, knaack.h@....de, lars@...afoo.de,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] iio: adc: ti-ads7950: inconsistency with spi msg

On 1/25/19 10:20 AM, justinpopo6@...il.com wrote:
> From: Justin Chen <justinpopo6@...il.com>
> 
> To read a channel we require 3 cycles to send, process, and receive
> the data. The transfer buffer for the third transaction is left blank.
> This leaves it up to the SPI driver to decide what to do.
> 
> In one particular case, if the tx buffer is not set the spi driver
> sets it to 0xff. This puts the ADC in a alarm programming state,
> therefore the following read to a channel becomes erroneous.
> 
> Instead of leaving us to the mercy of the SPI driver, we send the
> ADC cmd on the third transaction to prevent inconsistent behavior.
> 
> Fixes: 902c4b2446d4 ("iio: adc: New driver for TI ADS7950 chips")
> Signed-off-by: Justin Chen <justinpopo6@...il.com>

Reviewed-by: Florian Fainelli <f.fainelli@...il.com>

Thanks!
-- 
Florian