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Mon, 27 Jan 2025 10:12:32 -0500 From: Jonathan Santos To: , , CC: Jonathan Santos , , , , , , , , , Subject: [PATCH v2 06/16] iio: adc: ad7768-1: set MOSI idle state to prevent accidental reset Date: Mon, 27 Jan 2025 12:12:29 -0300 Message-ID: X-Mailer: git-send-email 2.34.1 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-ADIRuleOP-NewSCL: Rule Triggered X-Proofpoint-ORIG-GUID: RU-F9FZJ5HaHDCGbpOvY-t2wMaH0LSA0 X-Proofpoint-GUID: RU-F9FZJ5HaHDCGbpOvY-t2wMaH0LSA0 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1057,Hydra:6.0.680,FMLib:17.12.68.34 definitions=2025-01-27_07,2025-01-27_01,2024-11-22_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 bulkscore=0 malwarescore=0 lowpriorityscore=0 mlxlogscore=994 phishscore=0 adultscore=0 suspectscore=0 clxscore=1015 mlxscore=0 priorityscore=1501 impostorscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.19.0-2411120000 definitions=main-2501270121 Content-Type: text/plain; charset="utf-8" Datasheet recommends Setting the MOSI idle state to high in order to prevent accidental reset of the device when SCLK is free running. This happens when the controller clocks out a 1 followed by 63 zeros while the CS is held low. Check if SPI controller supports SPI_MOSI_IDLE_HIGH flag and set it. Fixes: a5f8c7da3dbe ("iio: adc: Add AD7768-1 ADC basic support") Signed-off-by: Jonathan Santos --- v2 Changes: * Only setup SPI_MOSI_IDLE_HIGH flag if the controller supports it, otherwi= se the driver continues the same. I realized that using bits_per_word does not avoid th= e problem that MOSI idle state is trying to solve. If the controller drives the MOSI low= between bytes during a transfer, nothing happens. --- drivers/iio/adc/ad7768-1.c | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) diff --git a/drivers/iio/adc/ad7768-1.c b/drivers/iio/adc/ad7768-1.c index c3cf04311c40..95ba89435652 100644 --- a/drivers/iio/adc/ad7768-1.c +++ b/drivers/iio/adc/ad7768-1.c @@ -574,6 +574,22 @@ static int ad7768_probe(struct spi_device *spi) return -ENOMEM; =20 st =3D iio_priv(indio_dev); + /* + * Datasheet recommends SDI line to be kept high when + * data is not being clocked out of the controller + * and the spi clock is free running, to prevent + * accidental reset. + * Since many controllers do not support the + * SPI_MOSI_IDLE_HIGH flag yet, only request the MOSI + * idle state to enable if the controller supports it. + */ + if (spi->controller->mode_bits & SPI_MOSI_IDLE_HIGH) { + spi->mode |=3D SPI_MOSI_IDLE_HIGH; + ret =3D spi_setup(spi); + if (ret < 0) + return ret; + } + st->spi =3D spi; =20 st->vref =3D devm_regulator_get(&spi->dev, "vref"); --=20 2.34.1