From mboxrd@z Thu Jan 1 00:00:00 1970 From: Marc Kleine-Budde Subject: Re: [PATCH V2 2/4] can: m_can: workaround for transmit data less than 4 bytes Date: Wed, 05 Nov 2014 11:17:48 +0100 Message-ID: <5459F94C.1030506@pengutronix.de> References: <1415174326-6623-1-git-send-email-b29396@freescale.com> <1415174326-6623-2-git-send-email-b29396@freescale.com> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="e0LjrM5Dx3cFj3uw6fqiW2j5xb6IrhK6B" Cc: wg@grandegger.com, varkabhadram@gmail.com, netdev@vger.kernel.org, socketcan@hartkopp.net, linux-arm-kernel@lists.infradead.org To: Dong Aisheng , linux-can@vger.kernel.org Return-path: In-Reply-To: <1415174326-6623-2-git-send-email-b29396@freescale.com> Sender: linux-can-owner@vger.kernel.org List-Id: netdev.vger.kernel.org This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --e0LjrM5Dx3cFj3uw6fqiW2j5xb6IrhK6B Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable On 11/05/2014 08:58 AM, Dong Aisheng wrote: > At least on the i.MX6SX with M_CAN IP version 3.0.x, an issue with Can you add the imx mask revision, too and the exact m_can version (is available). > the Message RAM was discovered. Sending CAN frames with dlc less > than 4 bytes will lead to bit errors, when the first 8 bytes of > the Message RAM have not been initialized (i.e. written to). > To work around this issue, the first 8 bytes are initialized in open() > function. >=20 > Without the workaround, we can easily see the following errors: > root@imx6qdlsolo:~# ip link set can0 up type can bitrate 1000000 > [ 66.882520] IPv6: ADDRCONF(NETDEV_CHANGE): can0: link becomes ready > root@imx6qdlsolo:~# cansend can0 123#112233 > [ 66.935640] m_can 20e8000.can can0: Bit Error Uncorrected >=20 > Signed-off-by: Dong Aisheng > --- > ChangeLog since v1: > * initialize the first 8 bytes of Tx Buffer of Message RAM in open() > to workaround the issue > --- > drivers/net/can/m_can/m_can.c | 9 +++++++++ > 1 file changed, 9 insertions(+) >=20 > diff --git a/drivers/net/can/m_can/m_can.c b/drivers/net/can/m_can/m_ca= n.c > index 664fe30..f47c200 100644 > --- a/drivers/net/can/m_can/m_can.c > +++ b/drivers/net/can/m_can/m_can.c > @@ -902,6 +902,15 @@ static void m_can_chip_config(struct net_device *d= ev) > /* set bittiming params */ > m_can_set_bittiming(dev); > =20 > + /* At least on the i.MX6SX with M_CAN IP version 3.0.x, an issue with= > + * the Message RAM was discovered. Sending CAN frames with dlc less > + * than 4 bytes will lead to bit errors, when the first 8 bytes of > + * the Message RAM have not been initialized (i.e. written to). > + * To work around this issue, the first 8 bytes are initialized here.= > + */ > + m_can_fifo_write(priv, 0, M_CAN_FIFO_DATA(0), 0x0); > + m_can_fifo_write(priv, 0, M_CAN_FIFO_DATA(1), 0x0); > + > m_can_config_endisable(priv, false); > } > =20 >=20 Marc --=20 Pengutronix e.K. | Marc Kleine-Budde | Industrial Linux Solutions | Phone: +49-231-2826-924 | Vertretung West/Dortmund | Fax: +49-5121-206917-5555 | Amtsgericht Hildesheim, HRA 2686 | http://www.pengutronix.de | --e0LjrM5Dx3cFj3uw6fqiW2j5xb6IrhK6B Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iQIcBAEBAgAGBQJUWflMAAoJECte4hHFiupUKlYQAJQ3rjPY+6SLHlRtDr3hetHd WT0AQpcmSs0HGCxQXe5i7TlN2dR+tyiC6r8TSVDBzUwETV77fwufWzQTp2b8fy3L KJiEHxVnQGaU5g3m+EAZO3rJHndvWeruW9Zpmzoy/FSvPlGpQO3uiTPj/hhtI2T0 DXBUdtgDf4pIbaPjOLQE7Gdd1DNdcyFZwZ2XZb6nUqusliBCwbO87Aat92WjbELX +H0ukQggjVF5rddsKPWVNEl4H0CsdjkZHjDL21C1D++RYAZMOv9rmYiWNoDmZPel d6RnnB72nEq4T0OIldmAvZnQa5Fkdvc9Nns2IQ/3wU8zBjKslLm8UgZG8eR11Xpw q0fxn2o+/vOK7mpN0RhnXHffRacEQKpVBkPQP5+kvpsvT6LHgXBG9FqYIi4Xsa8h tDIl7npJ8D6N35fJ32ekxYpTULaOKS58siRwkcB+5iG4FF8zYLIK4LFF/9B7reLU Ih7POTLeKzIr+G4kQvNgLeSJEHj77xsJAi4dZKo1f4HBcDnjn6YIjgFcIIt0QqoL ANTHT/Rv3yiUQowzOi3R3RqptT9ydelXNCD/6iN+lGI1YN8XrXrKQE+/uTbnlA07 K1ZyYEMwRqhGKyWINYdm0jFPLra1mnE9aMnK6bximLbi4wQrS5DSc7oZETfjR6wB E6mcUBSdQRYcPHK1USiY =WITG -----END PGP SIGNATURE----- --e0LjrM5Dx3cFj3uw6fqiW2j5xb6IrhK6B--