From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id AFA3FC77B75 for ; Tue, 23 May 2023 06:53:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232666AbjEWGxG (ORCPT ); Tue, 23 May 2023 02:53:06 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46566 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232057AbjEWGxB (ORCPT ); Tue, 23 May 2023 02:53:01 -0400 Received: from mail-pl1-x636.google.com (mail-pl1-x636.google.com [IPv6:2607:f8b0:4864:20::636]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B1CF1118; Mon, 22 May 2023 23:52:59 -0700 (PDT) Received: by mail-pl1-x636.google.com with SMTP id d9443c01a7336-1ae79528d4dso46303095ad.2; Mon, 22 May 2023 23:52:59 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20221208; t=1684824779; x=1687416779; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:sender:from:to:cc:subject:date :message-id:reply-to; bh=pHVJOrZTLhWxfI/dA1jc/7StnNnfOvKPoL5oGZLJdis=; b=mCssCrHbRZzxaj8bWmxvVy63hBj2eLFh5dSTr4sfFOMScdQYPJ4mpxJUP9Hu5mxx12 FCjR7liO0CSm2do/4NiubfpRliyKtLT3v15PzXqRmGeze0VRti85inMdTVpxwxeN2OpI p94QNGuigm3z62c59zixUlpXCzmvl3INRJaT0RDvyXF1BTBABuN5GuKNkXQgxOiwp6zS GgETo9PQvH4CB72r6TW/tWbf6RUnC1zeqxDHMFaEtXHjGV7NX8xQCT1DJBnVFzqSxp74 pwbGL03u+GADOja3nTV/vjd5hcaKLVFCOnux/KDPH2a5EpAyXbY9MgEuRl3Xwy4oUZeT xj+g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1684824779; x=1687416779; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:sender:x-gm-message-state:from :to:cc:subject:date:message-id:reply-to; bh=pHVJOrZTLhWxfI/dA1jc/7StnNnfOvKPoL5oGZLJdis=; b=L2zhi7I3nDRW4ORPQDw7FVvQ7eB+KUkuhN7QboZLz6CO+xjqs5z0jhDdoNTCT1Xsjm HZ2k3ZxurAbSRKQRwNSpeG3aYvddWpnkEEPi0oRyyO2aJFBxRVEYOIlXsEXTPTk9mr46 tBWNtKICUTXu61hi8lb8ksNlmXVfWHIIXh7LY2x1xKZSEN7L+dvlxNAKAFlz279l1Wyj 7ns158LV5RDO4/5Yy1RSpGrXtHjOyCiJPjjgKzvZSiu8+yJwbA0cmf7lgQZCw7GaodYZ i5lfu6y+8gm8yt5acxIL08gVNdE1eyS1lCf+hlQVJ71bwSjs04+DyMyYxW5rGgcMmyHu 9S9g== X-Gm-Message-State: AC+VfDyjaRy0GwqXHdDnTWyj58RmCC2zDMHl6jCNHSiN//gxnz06eb+6 JZyjuF5o9QJ0c5SypNYbsLUU7LeVnZ4= X-Google-Smtp-Source: ACHHUZ56VO7pRIv3NwujIPlTt9j7JaggLiXDEl86vjoqZ8eleL2NRPo30ZftRRxYForZv7Uaf0/DWw== X-Received: by 2002:a17:902:d04a:b0:1ac:5b6b:df4c with SMTP id l10-20020a170902d04a00b001ac5b6bdf4cmr10768105pll.69.1684824779002; Mon, 22 May 2023 23:52:59 -0700 (PDT) Received: from XH22050090-L.ad.ts.tri-ad.global ([103.175.111.222]) by smtp.gmail.com with ESMTPSA id d10-20020a170902ceca00b001aafa2e212esm5963920plg.52.2023.05.22.23.52.57 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 22 May 2023 23:52:58 -0700 (PDT) Sender: Vincent Mailhol From: Vincent Mailhol To: Marc Kleine-Budde , linux-can@vger.kernel.org, Thomas.Kopp@microchip.com Cc: Oliver Hartkopp , netdev@vger.kernel.org, marex@denx.de, Vincent Mailhol Subject: [PATCH v2 3/3] can: length: refactor frame lengths definition to add size in bits Date: Tue, 23 May 2023 15:52:18 +0900 Message-Id: <20230523065218.51227-4-mailhol.vincent@wanadoo.fr> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20230523065218.51227-1-mailhol.vincent@wanadoo.fr> References: <20230507155506.3179711-1-mailhol.vincent@wanadoo.fr> <20230523065218.51227-1-mailhol.vincent@wanadoo.fr> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-can@vger.kernel.org Introduce a method to calculate the exact size in bits of a CAN(-FD) frame with or without dynamic bitsuffing. These are all the possible combinations taken into account: - Classical CAN or CAN-FD - Standard or Extended frame format - CAN-FD CRC17 or CRC21 - Include or not intermission Instead of doing several macro definitions, declare the can_frame_bits() static inline function. To this extend, do a full refactoring of the length definitions. If given integer constant expressions as argument, can_frame_bits() folds into a compile time constant expression, giving no penalty over the use of macros. Also add the can_frame_bytes(). This function replaces the existing macro: - CAN_FRAME_OVERHEAD_SFF: can_frame_bytes(false, false, 0) - CAN_FRAME_OVERHEAD_EFF: can_frame_bytes(false, true, 0) - CANFD_FRAME_OVERHEAD_SFF: can_frame_bytes(true, false, 0) - CANFD_FRAME_OVERHEAD_EFF: can_frame_bytes(true, true, 0) The different frame lengths (including intermission) are as follow: Frame type bits bytes ---------------------------------------------------------- Classic CAN SFF no-bitstuffing 111 14 Classic CAN EFF no-bitstuffing 131 17 Classic CAN SFF bitstuffing 135 17 Classic CAN EFF bitstuffing 160 20 CAN-FD SFF no-bitstuffing 579 73 CAN-FD EFF no-bitstuffing 598 75 CAN-FD SFF bitstuffing 712 89 CAN-FD EFF bitstuffing 736 92 The macro CAN_FRAME_LEN_MAX and CANFD_FRAME_LEN_MAX are kept to be used in const struct declarations (folding of can_frame_bytes() occurs too late in the compilation to be used in struct declarations). In addition to the above: - Use ISO 11898-1:2015 definitions for the name of the CAN frame fields. - Include linux/bits.h for use of BITS_PER_BYTE. - Include linux/math.h for use of mult_frac() and DIV_ROUND_UP(). N.B: the use of DIV_ROUND_UP() is not new to this patch, but the include was previously omitted. - Add copyright 2023 for myself. [1] commit 85d99c3e2a13 ("can: length: can_skb_get_frame_len(): introduce function to get data length of frame in data link layer") Link: https://git.kernel.org/torvalds/c/85d99c3e2a13 [2] RE: [PATCH] can: mcp251xfd: Increase poll timeout Link: https://lore.kernel.org/linux-can/BL3PR11MB64846C83ACD04E9330B0FE66FB729@BL3PR11MB6484.namprd11.prod.outlook.com/ Signed-off-by: Vincent Mailhol --- In case you ask, here is the proof that can_frame_bits() folds into a compile time constant expression. This file: #include unsigned int canfd_max_len_bitsuffing(void) { return can_frame_bytes(true, true, true, CANFD_MAX_DLEN); } Produces this assembly code: 0000000000000010 : 10: f3 0f 1e fa endbr64 14: b8 5c 00 00 00 mov $0x5c,%eax 19: e9 00 00 00 00 jmpq 1e where 0x5c corresponds to the expected value of 92 bytes. --- drivers/net/can/dev/length.c | 15 +- include/linux/can/length.h | 326 +++++++++++++++++++++++++---------- 2 files changed, 238 insertions(+), 103 deletions(-) diff --git a/drivers/net/can/dev/length.c b/drivers/net/can/dev/length.c index b48140b1102e..b7f4d76dd444 100644 --- a/drivers/net/can/dev/length.c +++ b/drivers/net/can/dev/length.c @@ -78,18 +78,7 @@ unsigned int can_skb_get_frame_len(const struct sk_buff *skb) else len = cf->len; - if (can_is_canfd_skb(skb)) { - if (cf->can_id & CAN_EFF_FLAG) - len += CANFD_FRAME_OVERHEAD_EFF; - else - len += CANFD_FRAME_OVERHEAD_SFF; - } else { - if (cf->can_id & CAN_EFF_FLAG) - len += CAN_FRAME_OVERHEAD_EFF; - else - len += CAN_FRAME_OVERHEAD_SFF; - } - - return len; + return can_frame_bytes(can_is_canfd_skb(skb), cf->can_id & CAN_EFF_FLAG, + false, len); } EXPORT_SYMBOL_GPL(can_skb_get_frame_len); diff --git a/include/linux/can/length.h b/include/linux/can/length.h index 521fdbce2d69..7518117ee5fc 100644 --- a/include/linux/can/length.h +++ b/include/linux/can/length.h @@ -1,132 +1,278 @@ /* SPDX-License-Identifier: GPL-2.0 */ /* Copyright (C) 2020 Oliver Hartkopp * Copyright (C) 2020 Marc Kleine-Budde - * Copyright (C) 2020 Vincent Mailhol + * Copyright (C) 2020, 2023 Vincent Mailhol */ #ifndef _CAN_LENGTH_H #define _CAN_LENGTH_H +#include #include #include +#include /* - * Size of a Classical CAN Standard Frame + * Size of a Classical CAN Standard Frame header in bits + * + * Name of Field Bits + * --------------------------------------------------------- + * Start Of Frame (SOF) 1 + * Arbitration field: + * base ID 11 + * Remote Transmission Request (RTR) 1 + * Control field: + * IDentifier Extension bit (IDE) 1 + * FD Format indicatior (FDF) 1 + * Data Length Code (DLC) 4 + * + * including all fields preceding the data field, ignoring bitstuffing + */ +#define CAN_FRAME_HEADER_SFF_BITS 19 + +/* + * Size of a Classical CAN Extended Frame header in bits + * + * Name of Field Bits + * --------------------------------------------------------- + * Start Of Frame (SOF) 1 + * Arbitration field: + * base ID 11 + * Substitute Remote Request (SRR) 1 + * IDentifier Extension bit (IDE) 1 + * ID extension 18 + * Remote Transmission Request (RTR) 1 + * Control field: + * FD Format indicatior (FDF) 1 + * Reserved bit (r0) 1 + * Data length code (DLC) 4 + * + * including all fields preceding the data field, ignoring bitstuffing + */ +#define CAN_FRAME_HEADER_EFF_BITS 39 + +/* + * Size of a CAN-FD Standard Frame in bits + * + * Name of Field Bits + * --------------------------------------------------------- + * Start Of Frame (SOF) 1 + * Arbitration field: + * base ID 11 + * Remote Request Substitution (RRS) 1 + * Control field: + * IDentifier Extension bit (IDE) 1 + * FD Format indicator (FDF) 1 + * Reserved bit (res) 1 + * Bit Rate Switch (BRS) 1 + * Error Status Indicator (ESI) 1 + * Data length code (DLC) 4 + * + * including all fields preceding the data field, ignoring bitstuffing + */ +#define CANFD_FRAME_HEADER_SFF_BITS 22 + +/* + * Size of a CAN-FD Extended Frame in bits + * + * Name of Field Bits + * --------------------------------------------------------- + * Start Of Frame (SOF) 1 + * Arbitration field: + * base ID 11 + * Substitute Remote Request (SRR) 1 + * IDentifier Extension bit (IDE) 1 + * ID extension 18 + * Remote Request Substitution (RRS) 1 + * Control field: + * FD Format indicator (FDF) 1 + * Reserved bit (res) 1 + * Bit Rate Switch (BRS) 1 + * Error Status Indicator (ESI) 1 + * Data length code (DLC) 4 + * + * including all fields preceding the data field, ignoring bitstuffing + */ +#define CANFD_FRAME_HEADER_EFF_BITS 41 + +/* + * Size of a CAN CRC Field in bits + * + * Name of Field Bits + * --------------------------------------------------------- + * CRC sequence (CRC15) 15 + * CRC Delimiter 1 + * + * ignoring bitstuffing + */ +#define CAN_FRAME_CRC_FIELD_BITS 16 + +/* + * Size of a CAN-FD CRC17 Field in bits (length: 0..16) + * + * Name of Field Bits + * --------------------------------------------------------- + * Stuff Count 4 + * CRC Sequence (CRC17) 17 + * CRC Delimiter 1 + * Fixed stuff bits 6 + */ +#define CANFD_FRAME_CRC17_FIELD_BITS 28 + +/* + * Size of a CAN-FD CRC21 Field in bits (length: 20..64) + * + * Name of Field Bits + * --------------------------------------------------------- + * Stuff Count 4 + * CRC sequence (CRC21) 21 + * CRC Delimiter 1 + * Fixed stuff bits 7 + */ +#define CANFD_FRAME_CRC21_FIELD_BITS 33 + +/* + * Size of a CAN(-FD) Frame footer in bits * * Name of Field Bits * --------------------------------------------------------- - * Start-of-frame 1 - * Identifier 11 - * Remote transmission request (RTR) 1 - * Identifier extension bit (IDE) 1 - * Reserved bit (r0) 1 - * Data length code (DLC) 4 - * Data field 0...64 - * CRC 15 - * CRC delimiter 1 * ACK slot 1 * ACK delimiter 1 - * End-of-frame (EOF) 7 - * Inter frame spacing 3 + * End Of Frame (EOF) 7 * - * rounded up and ignoring bitstuffing + * including all fields following the CRC field */ -#define CAN_FRAME_OVERHEAD_SFF DIV_ROUND_UP(47, 8) +#define CAN_FRAME_FOOTER_BITS 9 /* - * Size of a Classical CAN Extended Frame - * - * Name of Field Bits - * --------------------------------------------------------- - * Start-of-frame 1 - * Identifier A 11 - * Substitute remote request (SRR) 1 - * Identifier extension bit (IDE) 1 - * Identifier B 18 - * Remote transmission request (RTR) 1 - * Reserved bits (r1, r0) 2 - * Data length code (DLC) 4 - * Data field 0...64 - * CRC 15 - * CRC delimiter 1 - * ACK slot 1 - * ACK delimiter 1 - * End-of-frame (EOF) 7 - * Inter frame spacing 3 - * - * rounded up and ignoring bitstuffing + * First part of the Inter Frame Space + * (a.k.a. IMF - intermission field) */ -#define CAN_FRAME_OVERHEAD_EFF DIV_ROUND_UP(67, 8) +#define CAN_INTERMISSION_BITS 3 /* - * Size of a CAN-FD Standard Frame + * CAN bit stuffing overhead multiplication factor * - * Name of Field Bits - * --------------------------------------------------------- - * Start-of-frame 1 - * Identifier 11 - * Remote Request Substitution (RRS) 1 - * Identifier extension bit (IDE) 1 - * Flexible data rate format (FDF) 1 - * Reserved bit (r0) 1 - * Bit Rate Switch (BRS) 1 - * Error Status Indicator (ESI) 1 - * Data length code (DLC) 4 - * Data field 0...512 - * Stuff Bit Count (SBC) 4 - * CRC 0...16: 17 20...64:21 - * CRC delimiter (CD) 1 - * Fixed Stuff bits (FSB) 0...16: 6 20...64:7 - * ACK slot (AS) 1 - * ACK delimiter (AD) 1 - * End-of-frame (EOF) 7 - * Inter frame spacing 3 + * The worst bit stuffing case is a sequence in which dominant and + * recessive bits alternate every four bits: * - * assuming CRC21, rounded up and ignoring dynamic bitstuffing + * Destuffed: 1 1111 0000 1111 0000 1111 + * Stuffed: 1 1111o 0000i 1111o 0000i 1111o + * + * Nomenclature: + * + * - "0": dominant bit + * - "o": dominant stuff bit + * - "1": recessive bit + * - "i": recessive stuff bit + * + * Ignoring the first bit, one stuff bit is added every four bits + * giving us an overhead of 1/4 = 0.25. */ -#define CANFD_FRAME_OVERHEAD_SFF DIV_ROUND_UP(67, 8) +#define can_bit_stuffing_overhead(stream_len) mult_frac(stream_len, 1, 4) + +/** + * can_frame_bits() - Calculate the number of bits in on the wire in a + * CAN frame + * @is_eff: true: Extended Frame; false: Standard Frame. + * @bitstuffing: if true, calculate the bitsuffing worst case, if + * false, calculated the bitsuffing best case (no dynamic + * bitsuffing). Fixed stuff bits always get included. + * @intermission: if and only if true, include the inter frame space + * assuming no bus idle (i.e. only the intermission gets added). + * @data_len: length of the data field in bytes. Correspond to + * can(fd)_frame->len. Should be zero for remote frames. No + * sanitization is done on @data_len. + * + * Return: the numbers of bits on the wire of a CAN frame. + */ +static inline +unsigned int can_frame_bits(bool is_fd, bool is_eff, + bool bitstuffing, bool intermission, + unsigned int data_len) +{ + unsigned int bits; + + if (is_fd) { + if (is_eff) + bits = CANFD_FRAME_HEADER_EFF_BITS; + else + bits = CANFD_FRAME_HEADER_SFF_BITS; + } else { + if (is_eff) + bits = CAN_FRAME_HEADER_EFF_BITS; + else + bits = CAN_FRAME_HEADER_SFF_BITS; + } + + bits += data_len * BITS_PER_BYTE; + + if (!is_fd) { + bits += CAN_FRAME_CRC_FIELD_BITS; + /* + * In Classical CAN, bit stuffing applies to all field + * from SOF to CRC delimiter + */ + if (bitstuffing) + bits += can_bit_stuffing_overhead(bits); + } else { + /* + * In CAN-FD, the fields preceding the CRC field have + * dynamic bit stuffing; but the CRC field has fixed + * bitstuffing + */ + if (bitstuffing) + bits += can_bit_stuffing_overhead(bits - 1); + if (data_len <= 16) + bits += CANFD_FRAME_CRC17_FIELD_BITS; + else + bits += CANFD_FRAME_CRC21_FIELD_BITS; + } + + bits += CAN_FRAME_FOOTER_BITS; + + if (intermission) + bits += CAN_INTERMISSION_BITS; + + return bits; +} /* - * Size of a CAN-FD Extended Frame - * - * Name of Field Bits - * --------------------------------------------------------- - * Start-of-frame 1 - * Identifier A 11 - * Substitute remote request (SRR) 1 - * Identifier extension bit (IDE) 1 - * Identifier B 18 - * Remote Request Substitution (RRS) 1 - * Flexible data rate format (FDF) 1 - * Reserved bit (r0) 1 - * Bit Rate Switch (BRS) 1 - * Error Status Indicator (ESI) 1 - * Data length code (DLC) 4 - * Data field 0...512 - * Stuff Bit Count (SBC) 4 - * CRC 0...16: 17 20...64:21 - * CRC delimiter (CD) 1 - * Fixed Stuff bits (FSB) 0...16: 6 20...64:7 - * ACK slot (AS) 1 - * ACK delimiter (AD) 1 - * End-of-frame (EOF) 7 - * Inter frame spacing 3 - * - * assuming CRC21, rounded up and ignoring dynamic bitstuffing + * Number of bytes in a CAN frame + * (rounded up, including intermission) */ -#define CANFD_FRAME_OVERHEAD_EFF DIV_ROUND_UP(86, 8) +static inline +unsigned int can_frame_bytes(bool is_fd, bool is_eff, bool bitstuffing, + unsigned int data_len) +{ + return DIV_ROUND_UP(can_frame_bits(is_fd, is_eff, bitstuffing, true, + data_len), + BITS_PER_BYTE); +} /* * Maximum size of a Classical CAN frame - * (rounded up and ignoring bitstuffing) + * (rounded up, ignoring bitstuffing but including intermission) */ -#define CAN_FRAME_LEN_MAX (CAN_FRAME_OVERHEAD_EFF + CAN_MAX_DLEN) +#define CAN_FRAME_LEN_MAX \ + DIV_ROUND_UP(CAN_FRAME_HEADER_EFF_BITS + \ + CAN_MAX_DLEN * BITS_PER_BYTE + \ + CAN_FRAME_CRC_FIELD_BITS + \ + CAN_FRAME_FOOTER_BITS + \ + CAN_INTERMISSION_BITS, \ + BITS_PER_BYTE) /* * Maximum size of a CAN-FD frame * (rounded up and ignoring bitstuffing) */ -#define CANFD_FRAME_LEN_MAX (CANFD_FRAME_OVERHEAD_EFF + CANFD_MAX_DLEN) +#define CANFD_FRAME_LEN_MAX \ + DIV_ROUND_UP(CANFD_FRAME_HEADER_EFF_BITS + \ + CANFD_MAX_DLEN * BITS_PER_BYTE + \ + CANFD_FRAME_CRC21_FIELD_BITS \ + CAN_FRAME_FOOTER_BITS + \ + CAN_INTERMISSION_BITS, \ + BITS_PER_BYTE) /* * can_cc_dlc2len(value) - convert a given data length code (dlc) of a -- 2.25.1