From mboxrd@z Thu Jan 1 00:00:00 1970 From: mkl@pengutronix.de (Marc Kleine-Budde) Date: Tue, 04 Nov 2014 14:28:52 +0100 Subject: [PATCH 7/7] can: m_can: workaround for transmit data less than 4 bytes In-Reply-To: <5458D0FA.1040504@hartkopp.net> References: <1414579527-31100-1-git-send-email-b29396@freescale.com> <1414579527-31100-7-git-send-email-b29396@freescale.com> <5457B1D1.6080301@pengutronix.de> <20141104082505.GA8060@shlinux1.ap.freescale.net> <54589AC8.4010106@pengutronix.de> <20141104092651.GC8060@shlinux1.ap.freescale.net> <5458AB65.7000500@pengutronix.de> <5458D0FA.1040504@hartkopp.net> Message-ID: <5458D494.3040700@pengutronix.de> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 11/04/2014 02:13 PM, Oliver Hartkopp wrote: > > > On 04.11.2014 11:33, Marc Kleine-Budde wrote: >> On 11/04/2014 10:27 AM, Dong Aisheng wrote: > > >>> + /* We meet an IC issue that we have to write the full 8 >> >> At least on the *insert SoC name here*, 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. > > Yes. Also put the current IP revision (3.0.x) into the comment. Good idea - also add the SoC's mask revision. > Did inform the Bosch guys from this issue - or is it already in some > errata sheet? > >> >>> + * bytes (whatever value for the second word) in Message RAM to >>> + * avoid bit error for transmit data less than 4 bytes at the >>> first >>> + * time. By initializing the first 8 bytes of tx buffer >>> before using >>> + * it can avoid such issue. >>> + */ >>> + 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); >>> } >> >> Can you trigger the issue when sending CAN-FD frames with dlc > 8 && dlc >> < 64? > > Just a nitpick: > > DLC can just be 0 .. 15 Correct, I was talking about the length > and the length (struct canfd_frame.len) can be from 0 .. 64 > > See: > > http://lxr.free-electrons.com/source/include/uapi/linux/can.h#L83 > > That's the reason for all these helpers > > http://lxr.free-electrons.com/source/drivers/net/can/dev.c#L36 > > that hide the evil "DLC" from userspace now and make 'len' a usable loop > variable as we were able to use the former dlc for classic CAN :-) Marc -- 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 | -------------- next part -------------- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 819 bytes Desc: OpenPGP digital signature URL: