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Wed, 19 Mar 2025 10:58:31 -0400 Received: from ASHBMBX9.ad.analog.com (10.64.17.10) by ASHBMBX9.ad.analog.com (10.64.17.10) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.986.14; Wed, 19 Mar 2025 10:58:31 -0400 Received: from zeus.spd.analog.com (10.66.68.11) by ashbmbx9.ad.analog.com (10.64.17.10) with Microsoft SMTP Server id 15.2.986.14 via Frontend Transport; Wed, 19 Mar 2025 10:58:31 -0400 Received: from work.ad.analog.com (HYB-hERzalRezfV.ad.analog.com [10.65.205.9]) by zeus.spd.analog.com (8.15.1/8.15.1) with ESMTP id 52JEwGho025155; Wed, 19 Mar 2025 10:58:19 -0400 From: Marcelo Schmitt To: , , CC: , , , , Subject: [PATCH v2 5/5] Documentation: iio: ad4000: Describe offload support Date: Wed, 19 Mar 2025 11:58:14 -0300 Message-ID: <888928d2224f5dad03a86b7108217f7b4b078979.1742394806.git.marcelo.schmitt@analog.com> X-Mailer: git-send-email 2.39.2 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-iio@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-ADIRuleOP-NewSCL: Rule Triggered X-Proofpoint-GUID: xLyDEITwn1BciJhWLMQe8dL_9ZQJsm7O X-Authority-Analysis: v=2.4 cv=J5+q7BnS c=1 sm=1 tr=0 ts=67dadb98 cx=c_pps a=3WNzaoukacrqR9RwcOSAdA==:117 a=3WNzaoukacrqR9RwcOSAdA==:17 a=Vs1iUdzkB0EA:10 a=wI1k2SEZAAAA:8 a=gAnH3GRIAAAA:8 a=zhJGIpXlanaEhhhmQREA:9 a=6HWbV-4b7c7AdzY24d_u:22 X-Proofpoint-ORIG-GUID: xLyDEITwn1BciJhWLMQe8dL_9ZQJsm7O X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1093,Hydra:6.0.680,FMLib:17.12.68.34 definitions=2025-03-19_05,2025-03-19_01,2024-11-22_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 bulkscore=0 spamscore=0 adultscore=0 priorityscore=1501 malwarescore=0 mlxlogscore=999 mlxscore=0 clxscore=1015 phishscore=0 suspectscore=0 lowpriorityscore=0 impostorscore=0 classifier=spam authscore=0 authtc=n/a authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2502280000 definitions=main-2503190101 When SPI offloading is supported, the IIO device provides different sysfs interfaces to allow using the adjusting the sample rate. Document SPI offload support for AD4000 and similar devices. Signed-off-by: Marcelo Schmitt Reviewed-by: David Lechner --- Documentation/iio/ad4000.rst | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) diff --git a/Documentation/iio/ad4000.rst b/Documentation/iio/ad4000.rst index 468d30dc9214..e490f9604b94 100644 --- a/Documentation/iio/ad4000.rst +++ b/Documentation/iio/ad4000.rst @@ -191,3 +191,25 @@ Typical voltage channel attributes of a differential AD4000 series device: +-------------------------------------------+------------------------------------------+ | ``in_voltage0-voltage1_scale_available`` | Toggles input span compression | +-------------------------------------------+------------------------------------------+ + +SPI offload support +------------------- + +To be able to achieve the maximum sample rate, the driver can be used with the +`AXI SPI Engine`_ to provide SPI offload support. + +.. _AXI SPI Engine: http://analogdevicesinc.github.io/hdl/projects/pulsar_adc/index.html + +When set for SPI offload support, the IIO device will provide different +interfaces. + +* Either ``in_voltage0_sampling_frequency`` or + ``in_voltage0-voltage1_sampling_frequency`` file is provided to allow setting + the sample rate. +* IIO trigger device is not provided (no ``trigger`` directory). +* ``timestamp`` channel is not provided. + +Also, because the ADC output has a one sample latency (delay) when the device is +wired in "3-wire" mode and only one transfer per sample is done when using SPI +offloading, the first data sample in the buffer is not valid because it contains +the output of an earlier conversion result.