From: Lars-Peter Clausen <lars@metafoo.de>
To: Alexandre Belloni <alexandre.belloni@bootlin.com>,
Jonathan Cameron <jic23@kernel.org>
Cc: Hartmut Knaack <knaack.h@gmx.de>,
Peter Meerwald-Stadler <pmeerw@pmeerw.net>,
Gregory CLEMENT <gregory.clement@bootlin.com>,
linux-iio@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/3] iio: adc: ti-ads8344: properly byte swap value
Date: Thu, 16 Apr 2020 08:29:45 +0200 [thread overview]
Message-ID: <696223d6-3804-0d22-7564-37161feca869@metafoo.de> (raw)
In-Reply-To: <20200415212257.161238-2-alexandre.belloni@bootlin.com>
On 4/15/20 11:22 PM, Alexandre Belloni wrote:
> The first received byte is the MSB, followed by the LSB so the value needs
> to be byte swapped.
>
> Also, the ADC actually has a delay of one clock on the SPI bus. Read three
> bytes to get the last bit.
>
> Fixes: 8dd2d7c0fed7 ("iio: adc: Add driver for the TI ADS8344 A/DC chips")
> Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
> ---
> drivers/iio/adc/ti-ads8344.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/iio/adc/ti-ads8344.c b/drivers/iio/adc/ti-ads8344.c
> index 9a460807d46d..6da50ea35217 100644
> --- a/drivers/iio/adc/ti-ads8344.c
> +++ b/drivers/iio/adc/ti-ads8344.c
> @@ -29,7 +29,6 @@ struct ads8344 {
> struct mutex lock;
>
> u8 tx_buf ____cacheline_aligned;
> - u16 rx_buf;
> };
>
> #define ADS8344_VOLTAGE_CHANNEL(chan, si) \
> @@ -76,6 +75,7 @@ static int ads8344_adc_conversion(struct ads8344 *adc, int channel,
> {
> struct spi_device *spi = adc->spi;
> int ret;
> + u8 buf[3];
Same as with spi_write(), spi_read() transfer buffers should not be on
the stack in case the driver tries to use it for DMA.
>
> adc->tx_buf = ADS8344_START;
> if (!differential)
> @@ -89,11 +89,11 @@ static int ads8344_adc_conversion(struct ads8344 *adc, int channel,
>
> udelay(9);
>
> - ret = spi_read(spi, &adc->rx_buf, 2);
> + ret = spi_read(spi, buf, sizeof(buf));
> if (ret)
> return ret;
>
> - return adc->rx_buf;
> + return buf[0] << 9 | buf[1] << 1 | buf[2] >> 7;
> }
>
> static int ads8344_read_raw(struct iio_dev *iio,
next prev parent reply other threads:[~2020-04-16 6:30 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-15 21:22 [PATCH 0/3] iio: adc: ti-ads8344: improve the driver Alexandre Belloni
2020-04-15 21:22 ` [PATCH 1/3] iio: adc: ti-ads8344: properly byte swap value Alexandre Belloni
2020-04-16 6:22 ` kbuild test robot
2020-04-16 20:50 ` Alexandre Belloni
2020-04-19 2:49 ` Philip Li
2020-04-21 7:25 ` Xia, Hui
2020-04-21 12:24 ` Alexandre Belloni
2020-04-16 6:29 ` Lars-Peter Clausen [this message]
2020-04-15 21:22 ` [PATCH 2/3] iio: adc: ti-ads8344: remove tx_buf from driver data Alexandre Belloni
2020-04-16 6:26 ` Lars-Peter Clausen
2020-04-17 10:24 ` Andy Shevchenko
2020-04-15 21:22 ` [PATCH 3/3] iio: adc: ti-ads8344: optimize consumption Alexandre Belloni
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=696223d6-3804-0d22-7564-37161feca869@metafoo.de \
--to=lars@metafoo.de \
--cc=alexandre.belloni@bootlin.com \
--cc=gregory.clement@bootlin.com \
--cc=jic23@kernel.org \
--cc=knaack.h@gmx.de \
--cc=linux-iio@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=pmeerw@pmeerw.net \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).