From patchwork Mon Jul 6 09:22:44 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Adrian Fiergolski X-Patchwork-Id: 1323475 Return-Path: X-Original-To: incoming-dt@patchwork.ozlabs.org Delivered-To: patchwork-incoming-dt@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=vger.kernel.org (client-ip=23.128.96.18; helo=vger.kernel.org; envelope-from=devicetree-owner@vger.kernel.org; receiver=) Authentication-Results: ozlabs.org; dmarc=none (p=none dis=none) header.from=fastree3d.com Authentication-Results: ozlabs.org; dkim=fail reason="signature verification failed" (2048-bit key; unprotected) header.d=fastree3d-com.20150623.gappssmtp.com header.i=@fastree3d-com.20150623.gappssmtp.com header.a=rsa-sha256 header.s=20150623 header.b=YSXvQNgx; dkim-atps=neutral Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by ozlabs.org (Postfix) with ESMTP id 4B0g9M35BLz9sSn for ; Mon, 6 Jul 2020 19:23:35 +1000 (AEST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728628AbgGFJXf (ORCPT ); Mon, 6 Jul 2020 05:23:35 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36672 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728603AbgGFJXe (ORCPT ); Mon, 6 Jul 2020 05:23:34 -0400 Received: from mail-ej1-x641.google.com (mail-ej1-x641.google.com [IPv6:2a00:1450:4864:20::641]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1D89AC08C5DF for ; Mon, 6 Jul 2020 02:23:34 -0700 (PDT) Received: by mail-ej1-x641.google.com with SMTP id dr13so41634458ejc.3 for ; Mon, 06 Jul 2020 02:23:34 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=fastree3d-com.20150623.gappssmtp.com; s=20150623; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=F6fo77lXw3Wa9Ww9ysq9BOqYKJ0fNyxAE2eRhCOsSNc=; b=YSXvQNgxeN2qzLB+St45pcHZ/m81Pnb4zyDkQ6gegeYhVS1FY7bXxEqEocf0voPJJU HKbqdCgjSddYDNZftx5Un7qw+elwZ3E/9wFERFyGKgxYtvL/QeAbUXnaPMSSjUEKKSRJ HqT+QsznvXgR15DfoNIvc3SClvGwGQuyZ3bWPD1o4r31Lv7hvUCd9UClHA0NgMz/O/VQ WJ8ukwPCwe6sn0vYfvKiIEYbr1B9mOYJCZSbnBIudMeL+lABv8K3O4E6YTLeJwBn4ZM7 2oisQMY8CXbrLw6VA96xX+P8O9XZk2fSJ3UWaMLalEY0QbKifD7Y8RdZ86AsSynSuqE0 hhVg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=F6fo77lXw3Wa9Ww9ysq9BOqYKJ0fNyxAE2eRhCOsSNc=; b=HlYUrPa19T6wLgN1nhqDuEABimh1ahLq+wM0mlkG1ew0s969lZkdm8j812dfqVmNa+ n7qI3NnZBmDMuK2S6pISiywKJvjoNUupSEfaVFjid55IwUloNfRDkNismiZZbHTRPOku BsK9voSQe++OY6YN5kbdRStHywJ30xR3WzUFK4g92IP971NRjI1a1LH+z5DDtdOMwCmi bn102UQpccfAYLVOU/L63sOUVzpfnpHbOUew0xd8GWCveh8O+Gw724a723RowTrOLkpD mPmL6bieDl3Z2ojYocbGNAMQqjeVBTStNvo4eOW+yV3pbbWc2+otgfPY3qOYmufK9ein 3Gzg== X-Gm-Message-State: AOAM531JYVubV6AaoGM2tLdmy7QCdzerp9CoN7AAlRp0jJbH6ROTOPpI qKx9IEk+dlIWGhM7fWi4wY1u X-Google-Smtp-Source: ABdhPJwpyAHaCGzluPP24M/BnJk1LROk9XKUZIbY7we5jc8pngCTX3YsRtf++tZzjXF0rmbzFu2NIg== X-Received: by 2002:a17:906:dbcf:: with SMTP id yc15mr32612198ejb.222.1594027412796; Mon, 06 Jul 2020 02:23:32 -0700 (PDT) Received: from localhost.localdomain (fastree1.epfl.ch. [192.26.37.52]) by smtp.gmail.com with ESMTPSA id bm21sm15895244ejb.13.2020.07.06.02.23.32 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 06 Jul 2020 02:23:32 -0700 (PDT) From: Adrian Fiergolski Cc: geert@linux-m68k.org, lukas@wunner.de, Adrian Fiergolski , Mark Brown , Rob Herring , linux-spi@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v2 2/2] dt-bindings: Add documentation for SPI daisy chain driver. Date: Mon, 6 Jul 2020 11:22:44 +0200 Message-Id: <20200706092247.20740-2-adrian.fiergolski@fastree3d.com> X-Mailer: git-send-email 2.27.0 In-Reply-To: <20200706092247.20740-1-adrian.fiergolski@fastree3d.com> References: <202007040833.xIqR5rAw%lkp@intel.com> <20200706092247.20740-1-adrian.fiergolski@fastree3d.com> MIME-Version: 1.0 To: unlisted-recipients:; (no To-header on input) Sender: devicetree-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org Add documentation for SPI daisy chain driver. Signed-off-by: Adrian Fiergolski --- .../bindings/spi/spi-daisy_chain.txt | 56 +++++++++++++++++++ 1 file changed, 56 insertions(+) create mode 100644 Documentation/devicetree/bindings/spi/spi-daisy_chain.txt diff --git a/Documentation/devicetree/bindings/spi/spi-daisy_chain.txt b/Documentation/devicetree/bindings/spi/spi-daisy_chain.txt new file mode 100644 index 000000000000..1e5b046dda83 --- /dev/null +++ b/Documentation/devicetree/bindings/spi/spi-daisy_chain.txt @@ -0,0 +1,56 @@ +spi-daisy_chain : The driver handling SPI daisy chains. +----------------------------------------------------------- + +Required properties: +- compatible : Should be "spi,daisy_chain" +- reg : Chip select assigned to the chain + + For the SPI devices on a common SPI chain - nodes of daisy_chain): +- spi-daisy-chain-len : Length (in bytes) of the SPI transfer, + when the SPI device is part of a device chain. +- spi-daisy-chain-noop : Byte string of no-operation command which should + be send when device is not addressed during the + given SPI transfer + +Optional properties: + (for the SPI devices on a common SPI chain (nodes of daisy_chain): +- spi-daisy-chain-bits_per_word : no-operation transfers involve + one or more words; word sizes like + eight or 12 bits are common. + In-memory wordsizes are powers of two + bytes (e.g. 20 bit samples use 32 bits). + If not defined, it is assumed to be 8. + +The daisy chain is a virtual device represented as a regular SPI device. Its +nodes define physical devices available on the chain. The order of the nodes +defines the order of the physical devices on the chain: MOSI pin of a device +represented by the first node is the last one on the MOSI daisy chain. The +daisy-chain functionality is transparent to the drivers of the physical devices +on the chain. All nodes share SPI mode, chip select and a max speed of the +virtual daisy chain device. Once one of the physical devices is being accessed, +the spi-daisy_chain driver combines this data with no-operation commands of all +other devices on the chain. + +Example: + + daisy_chain0: daisy_chain@0 { + compatible = "spi,daisy_chain"; + spi-max-frequency = <10000000>; + reg = <0>; + + dac0: ltc2632@0 { + compatible = "lltc,ltc2634-l12"; + spi-daisy-chain-len = <4>; + spi-daisy-chain-noop = [00 F0 00 00]; + }; + dac1: ltc2632@1 { + compatible = "lltc,ltc2634-l12"; + spi-daisy-chain-len = <4>; + spi-daisy-chain-noop = [00 F0 00 00]; + }; + dac2: ltc2632@2 { + compatible = "lltc,ltc2634-l12"; + spi-daisy-chain-len = <4>; + spi-daisy-chain-noop = [00 F0 00 00]; + }; + };