This is a note to let you know that I've just added the patch titled
iio: adc: ad7606: fix raw read for 18-bit chips
to my char-misc git tree which can be found at git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc.git in the char-misc-testing branch.
The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.)
The patch will be merged to the char-misc-next branch sometime soon, after it passes testing, and the merge window is open.
If you have any questions about this process, please let me know.
From 3f5fd1717ae9497215f22aa748fc2c09df88b0e3 Mon Sep 17 00:00:00 2001 From: David Lechner dlechner@baylibre.com Date: Fri, 2 May 2025 10:04:30 -0500 Subject: iio: adc: ad7606: fix raw read for 18-bit chips
Fix 18-bit raw read for 18-bit chips by applying a mask to the value we receive from the SPI controller.
SPI controllers either return 1, 2 or 4 bytes per word depending on the bits_per_word. For 16-bit chips, there was no problem since they raw data fit exactly in the 2 bytes received from the SPI controller. But now that we have 18-bit chips and we are using bits_per_word = 18, we cannot assume that the extra bits in the 32-bit word are always zero. In fact, with the AXI SPI Engine controller, these bits are not always zero which caused the raw values to read 10s of 1000s of volts instead of the correct value. Therefore, we need to mask the value we receive from the SPI controller to ensure that only the 18 bits of real data are used.
Fixes: f3838e934dff ("iio: adc: ad7606: add support for AD7606C-{16,18} parts") Signed-off-by: David Lechner dlechner@baylibre.com Link: https://patch.msgid.link/20250502-iio-adc-ad7606-fix-raw-read-for-18-bit-chi... Cc: Stable@vger.kernel.org Signed-off-by: Jonathan Cameron Jonathan.Cameron@huawei.com --- drivers/iio/adc/ad7606.c | 21 ++++++++++----------- 1 file changed, 10 insertions(+), 11 deletions(-)
diff --git a/drivers/iio/adc/ad7606.c b/drivers/iio/adc/ad7606.c index 703556eb7257..8ed65a35b486 100644 --- a/drivers/iio/adc/ad7606.c +++ b/drivers/iio/adc/ad7606.c @@ -727,17 +727,16 @@ static int ad7606_scan_direct(struct iio_dev *indio_dev, unsigned int ch, goto error_ret;
chan = &indio_dev->channels[ch + 1]; - if (chan->scan_type.sign == 'u') { - if (realbits > 16) - *val = st->data.buf32[ch]; - else - *val = st->data.buf16[ch]; - } else { - if (realbits > 16) - *val = sign_extend32(st->data.buf32[ch], realbits - 1); - else - *val = sign_extend32(st->data.buf16[ch], realbits - 1); - } + + if (realbits > 16) + *val = st->data.buf32[ch]; + else + *val = st->data.buf16[ch]; + + *val &= GENMASK(realbits - 1, 0); + + if (chan->scan_type.sign == 's') + *val = sign_extend32(*val, realbits - 1);
error_ret: if (!st->gpio_convst) {