forked from Minki/linux
e759c626d8
During test transmitting using CAN-FD at high bitrates (> 2 Mbps) would fail. Scoping the signals I noticed that only a single bit was being transmitted and with a bit more investigation realized the actual MCAN IP would go back to initialization mode automatically. It appears this issue is due to the MCAN needing to use the Transmitter Delay Compensation Mode with the correct value for the transmitter delay compensation offset (tdco). What impacts the tdco value isn't 100% clear but to calculate it you use an equation defined in the MCAN User's Guide. The user guide mentions that this register needs to be set based on clock values, secondary sample point and the data bitrate. One of the key variables that can't automatically be determined is the secondary sample point (ssp). This ssp is similar to the sp but is specific to this transmitter delay compensation mode. The guidelines for configuring ssp is rather vague but via some CAN test it appears for DRA76x that putting the value same as data sampling point works. The CAN-CIA's "Bit Time Requirements for CAN FD" paper presented at the International CAN Conference 2013 indicates that this TDC mode is only needed for data bit rates above 2.5 Mbps. Therefore, only enable this mode when the data bit rate is above 2.5 Mbps. Signed-off-by: Franklin S Cooper Jr <fcooper@ti.com> Signed-off-by: Sekhar Nori <nsekhar@ti.com> Signed-off-by: Faiz Abbas <faiz_abbas@ti.com> Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de> |
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| Kconfig | ||
| m_can.c | ||
| Makefile | ||