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 25F3AC433F5 for ; Thu, 13 Jan 2022 21:10:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234848AbiAMVKX (ORCPT ); Thu, 13 Jan 2022 16:10:23 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42560 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234890AbiAMVKX (ORCPT ); Thu, 13 Jan 2022 16:10:23 -0500 Received: from metis.ext.pengutronix.de (metis.ext.pengutronix.de [IPv6:2001:67c:670:201:290:27ff:fe1d:cc33]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id CECC0C061574 for ; Thu, 13 Jan 2022 13:10:22 -0800 (PST) Received: from gallifrey.ext.pengutronix.de ([2001:67c:670:201:5054:ff:fe8d:eefb] helo=bjornoya.blackshift.org) by metis.ext.pengutronix.de with esmtps (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1n87MT-0007dS-9w; Thu, 13 Jan 2022 22:10:21 +0100 Received: from pengutronix.de (unknown [195.138.59.174]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange ECDHE (P-256) server-signature RSA-PSS (4096 bits) server-digest SHA256) (Client did not present a certificate) (Authenticated sender: mkl-all@blackshift.org) by smtp.blackshift.org (Postfix) with ESMTPSA id 62C1018133; Thu, 13 Jan 2022 21:10:19 +0000 (UTC) Date: Thu, 13 Jan 2022 22:10:18 +0100 From: Marc Kleine-Budde To: Srinivas Neeli Cc: Srinivas Goud , Naveen Kumar Gaddipati , Prasad Beer Prasad , linux-can , Stefan =?utf-8?B?TcOkdGpl?= , Vincent MAILHOL Subject: Re: Queries on CAN frame work Message-ID: <20220113211018.tqddyiix3vy5q3eq@pengutronix.de> References: <20220113203004.jf2rqj2pirhgx72i@pengutronix.de> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="wv5znby7ov7f3bvj" Content-Disposition: inline In-Reply-To: <20220113203004.jf2rqj2pirhgx72i@pengutronix.de> X-SA-Exim-Connect-IP: 2001:67c:670:201:5054:ff:fe8d:eefb X-SA-Exim-Mail-From: mkl@pengutronix.de X-SA-Exim-Scanned: No (on metis.ext.pengutronix.de); SAEximRunCond expanded to false X-PTX-Original-Recipient: linux-can@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-can@vger.kernel.org --wv5znby7ov7f3bvj Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On 13.01.2022 21:30:04, Marc Kleine-Budde wrote: > > Recently we did few experiments with our CANFD network. Stuff error > > observed with different Nominal and Dataphase prescaler configuration > > values, which we get from the frame work. > >=20 > > For lower baud rates separate prescalers are working good, but when we > > switch to high baud rates(like 4Mbps and 5Mbps) observed the BUSOFF > > state(Due to stuff errors) on IP(Xilinx). > >=20 > > With shared prescaler(low prescalers) we are not seeing the issue.. > >=20 > > In Iso spec also mentioned to avoid tolerance, we have to maintain > > common TQ for Nominal and Data phase. This is a known problem with the current arbitration and data bit rate calculation. They are done independently of each other, resulting in not common pre-scalers and thus not common TQ. > > Spec: ISO 11898-1:2015(E) page no :50 > >=20 > > " If the same time quantum length is used in the nominal bit time and > > in the data bit time and the positions of the sample points in the > > nominal bit time are the same in all CAN nodes of a network, then > > optimum clock tolerance is accomplished for networks using FD frames." > >=20 > > CIA: > > https://can-newsletter.org/uploads/media/raw/f6a36d1461371a2f86ef0011a5= 13712c.pdf > >=20 > > From above CAN-newsletter also suggested the same in recommendation 2 a= nd 3. I'll have a look at the newsletter and see what changes need to be done to the existing algorithm. > > Recommendation 2: Set the BRPA bit-rate prescaler equal BRPB > > Recommendation 3: Choose BRPA and BRPD as low as possible > >=20 > > Is there any possibility in framework to use shared prescalars for > > Nominal and Dataphase?. Not yet. > > One more question. How to calculate TDCO ?, is there any generic > > formula for this ?. Vincent (Cc'ed) can help you on this. regards, Marc --=20 Pengutronix e.K. | Marc Kleine-Budde | Embedded Linux | https://www.pengutronix.de | Vertretung West/Dortmund | Phone: +49-231-2826-924 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 | --wv5znby7ov7f3bvj Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAABCgAdFiEEK3kIWJt9yTYMP3ehqclaivrt76kFAmHglTcACgkQqclaivrt 76mDEAgAk8PATw8kxRwiaSnMttpDpZvtNw0+DZv77W9c1QEMs2QS9M8GwYSEJm5X ISGemVa60BhUhi00ayTjF/KtPw5p1nDWV5zbVMonOWoEINxtVDnanag/sFmpL5eW 6DZSPdM/+eL7gUSdhGodaveqXBPRkpONRI6iZ1xuIT1uodQNKP3OAlPflbvzLVxm 8wBIkodc9G/JkZLnoQj9GkigxvClI2a/nCAl4+DMsaKlVaaXm3Re49oF1J+ptO0i Hzz++QXN4tSvq7LW0oHCwcLI5CeN1ucgv66QFrBDvG5Prgmombh9WBbWfm9ZHCM3 xY4L2ne9acCJSG+ggVm7iBLQq7A5Gg== =u+eM -----END PGP SIGNATURE----- --wv5znby7ov7f3bvj--