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 X-Spam-Level: X-Spam-Status: No, score=-3.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8F41AC4338F for ; Mon, 16 Aug 2021 12:33:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6B47363260 for ; Mon, 16 Aug 2021 12:33:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229879AbhHPMeD (ORCPT ); Mon, 16 Aug 2021 08:34:03 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37342 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234035AbhHPMdq (ORCPT ); Mon, 16 Aug 2021 08:33:46 -0400 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 B0212C061764 for ; Mon, 16 Aug 2021 05:33:14 -0700 (PDT) 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 1mFbnl-00010C-3c; Mon, 16 Aug 2021 14:33:13 +0200 Received: from pengutronix.de (unknown [IPv6:2a02:810a:8940:aa0:3272:cc96:80a9:1a01]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange ECDHE (P-384) 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 6482F6682CA; Mon, 16 Aug 2021 12:33:11 +0000 (UTC) Date: Mon, 16 Aug 2021 14:33:09 +0200 From: Marc Kleine-Budde To: Vincent MAILHOL Cc: linux-can , Stefan =?utf-8?B?TcOkdGpl?= , netdev , open list Subject: Re: [PATCH v5 2/7] can: bittiming: allow TDC{V,O} to be zero and add can_tdc_const::tdc{v,o,f}_min Message-ID: <20210816123309.pfa57tke5hrycqae@pengutronix.de> References: <20210815033248.98111-1-mailhol.vincent@wanadoo.fr> <20210815033248.98111-3-mailhol.vincent@wanadoo.fr> <20210816084235.fr7fzau2ce7zl4d4@pengutronix.de> <20210816122519.mme272z6tqrkyc6x@pengutronix.de> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="mous7h2ch4x6sr3w" Content-Disposition: inline In-Reply-To: <20210816122519.mme272z6tqrkyc6x@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 --mous7h2ch4x6sr3w Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On 16.08.2021 14:25:19, Marc Kleine-Budde wrote: > > > I'm not sure, if we talked about the mcp251xfd's tcdo, valid values a= re > > > -64...63. > >=20 > > Yes! Stefan shed some light on this. The mcp251xfd uses a tdco > > value which is relative to the sample point. >=20 > I don't read the documentation this way.... >=20 > > | SSP =3D TDCV + absolute TDCO > > | =3D TDCV + SP + relative TDCO > >=20 > > Consequently: > > | relative TDCO =3D absolute TDCO - SP >=20 > In the mcp15xxfd family manual > (http://ww1.microchip.com/downloads/en/DeviceDoc/MCP251XXFD-CAN-FD-Contro= ller-Module-Family-Reference-Manual-20005678B.pdf) > in the 2mbit/s data bit rate example in table 3-5 (page 21) it says: >=20 > | DTSEG1 15 DTQ > | DTSEG2 4 DTQ > | TDCO 15 DTQ >=20 > The mcp251xfd driver uses 15, the framework calculates 16 (=3D=3D Sync Se= g+ > tseg1, which is correct), and relative tdco would be 0: >=20 > | mcp251xfd_set_bittiming: tdco=3D15, priv->tdc.tdc=3D16, relative_tdco= =3D0 >=20 > Here the output with the patched ip tool: Sorry, the previous output was not using the sample points of the example in the data sheet, this is the fixed output: | 6: mcp251xfd0: mtu 72 qdisc pfifo_fast state UP = mode DEFAULT group default qlen 10 | link/can promiscuity 0 minmtu 0 maxmtu 0=20 | can state ERROR-ACTIVE (berr-counter tx 0 rx 0) restart= -ms 100=20 | bitrate 500000 sample-point 0.800 | tq 25 prop-seg 31 phase-seg1 32 phase-seg2 16 sjw 1 brp 1 | mcp251xfd: tseg1 2..256 tseg2 1..128 sjw 1..128 brp 1..256 brp_= inc 1 | dbitrate 2000000 dsample-point 0.800 | dtq 25 dprop-seg 7 dphase-seg1 8 dphase-seg2 4 dsjw 1 dbrp 1 | tdco 16 | mcp251xfd: dtseg1 1..32 dtseg2 1..16 dsjw 1..16 dbrp 1..256 dbr= p_inc 1 | tdco 0..127 | clock 40000000 numtxqueues 1 numrxqueues 1 gso_max_size 65536 g= so_max_segs 65535 parentbus spi parentdev spi0.0=20 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 | --mous7h2ch4x6sr3w Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAABCgAdFiEEK3kIWJt9yTYMP3ehqclaivrt76kFAmEaWwMACgkQqclaivrt 76mIdQf/ZjXMNJovC6gVsk7bpzr0KHJZB1YmUOFDoboV3Ghv/YuNx5X3nPbtM4S4 TrfQOhjkYVV6Xi0ONIygWnlUXQQP5GeemF8tbK1GeO9ZNaOexwjWU5/mR2xJQQki Ubj+wtI80hde07RVuDhQRTde3ugn5lzDtXFL6xYKJ5Zb9Nz/TUkxgbdluTj2v6lo VTbBpzJwZwMDtIlg/1MRRD79/DkOLLycAQCK4F6OhU6488hyPIJxLKFes1kq+1zE VpwuElW386P4g0BBjpP6sXmg9o1V3gSmdhkjYZHMCGBdz0zW4K7hCz6NAEzZGrS9 qH6HZnDStHbg1KECeadK+NwZdF0caw== =xVXe -----END PGP SIGNATURE----- --mous7h2ch4x6sr3w--