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: 11645285 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 65C9392A for ; Mon, 6 Jul 2020 09:23:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4E2FA2074F for ; Mon, 6 Jul 2020 09:23:35 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=fastree3d-com.20150623.gappssmtp.com header.i=@fastree3d-com.20150623.gappssmtp.com header.b="YSXvQNgx" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728620AbgGFJXe (ORCPT ); Mon, 6 Jul 2020 05:23:34 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36670 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728303AbgGFJXe (ORCPT ); Mon, 6 Jul 2020 05:23:34 -0400 Received: from mail-ej1-x643.google.com (mail-ej1-x643.google.com [IPv6:2a00:1450:4864:20::643]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1BF54C061794 for ; Mon, 6 Jul 2020 02:23:34 -0700 (PDT) Received: by mail-ej1-x643.google.com with SMTP id dp18so41615864ejc.8 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=ip4s/1mz3k0H/sgUhO4rKVyrrxTlI4MrDkZR/oeskSgIeVmyIspvH9DdzZ0Z8hWmzn T56ulU8RDsYUIrSpmcAYCb0wGiIrPLGxuieaStxEqsQXhkksymrGuXfPCITYYoYZAXPO peagQjcbTTIxNyTVGrLLArWDMZKBpEMIB0Tu8ONjRkMbCa4y0Ho/49OZDMtpiMH6L5Rc xt/ADTrgqc1Sbzx5p8q3eBhTbv2uc+uQ1LizjS6koN+IU+Ld86l8GfkeZEZdBheYqPwN GyxOPDy3hSANRbh4qZIVwqVO8zcjfieZptSWvB9W3ycdzLibL6NzM/I7fBLPSOsqwrF+ qfEg== X-Gm-Message-State: AOAM533RhdtAF3c7G4PBCV4Ix/XAhGpUBeCo3Nra2vC0664sg4vfllYC 9PjpuPmOJjOE4inRfPSHcVAM 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: linux-spi-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-spi@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]; + }; + };