From: Florian Fainelli <f.fainelli@gmail.com>
To: justinpopo6@gmail.com, linux-iio@vger.kernel.org
Cc: jic23@kernel.org, knaack.h@gmx.de, lars@metafoo.de,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] iio: adc: ti-ads7950: inconsistency with spi msg
Date: Thu, 24 Jan 2019 20:30:30 -0800 [thread overview]
Message-ID: <ac0a8ff6-92f5-09ef-932b-aba6378f1f47@gmail.com> (raw)
In-Reply-To: <1548381414-20561-1-git-send-email-justinpopo6@gmail.com>
Hi Justin,
On 1/24/19 5:56 PM, justinpopo6@gmail.com wrote:
> From: Justin Chen <justinpopo6@gmail.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.
Do you think this warrants a Fixes: tag?
>
> Signed-off-by: Justin Chen <justinpopo6@gmail.com>
> ---
> drivers/iio/adc/ti-ads7950.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/drivers/iio/adc/ti-ads7950.c b/drivers/iio/adc/ti-ads7950.c
> index 0ad6359..5453e10 100644
> --- a/drivers/iio/adc/ti-ads7950.c
> +++ b/drivers/iio/adc/ti-ads7950.c
> @@ -422,6 +422,7 @@ static int ti_ads7950_probe(struct spi_device *spi)
> st->scan_single_xfer[1].tx_buf = &st->single_tx;
> st->scan_single_xfer[1].len = 2;
> st->scan_single_xfer[1].cs_change = 1;
> + st->scan_single_xfer[2].rx_buf = &st->single_tx;
Should this be st->scan_single_xfer[2].tx_buf?
> st->scan_single_xfer[2].rx_buf = &st->single_rx;
> st->scan_single_xfer[2].len = 2;
>
>
--
Florian
next prev parent reply other threads:[~2019-01-25 4:30 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-25 1:56 [PATCH] iio: adc: ti-ads7950: inconsistency with spi msg justinpopo6
2019-01-25 4:30 ` Florian Fainelli [this message]
2019-01-25 5:56 ` Justin Chen
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