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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-11 08:27:49 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-11 08:27:49 +0000 |
commit | ace9429bb58fd418f0c81d4c2835699bddf6bde6 (patch) | |
tree | b2d64bc10158fdd5497876388cd68142ca374ed3 /Documentation/networking/device_drivers/can/freescale/flexcan.rst | |
parent | Initial commit. (diff) | |
download | linux-c5db43d0cef8c4615d5960c43ba45e6dbd0abc00.tar.xz linux-c5db43d0cef8c4615d5960c43ba45e6dbd0abc00.zip |
Adding upstream version 6.6.15.upstream/6.6.15
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'Documentation/networking/device_drivers/can/freescale/flexcan.rst')
-rw-r--r-- | Documentation/networking/device_drivers/can/freescale/flexcan.rst | 54 |
1 files changed, 54 insertions, 0 deletions
diff --git a/Documentation/networking/device_drivers/can/freescale/flexcan.rst b/Documentation/networking/device_drivers/can/freescale/flexcan.rst new file mode 100644 index 0000000000..106cd28901 --- /dev/null +++ b/Documentation/networking/device_drivers/can/freescale/flexcan.rst @@ -0,0 +1,54 @@ +.. SPDX-License-Identifier: GPL-2.0+ + +============================= +Flexcan CAN Controller driver +============================= + +Authors: Marc Kleine-Budde <mkl@pengutronix.de>, +Dario Binacchi <dario.binacchi@amarulasolutions.com> + +On/off RTR frames reception +=========================== + +For most flexcan IP cores the driver supports 2 RX modes: + +- FIFO +- mailbox + +The older flexcan cores (integrated into the i.MX25, i.MX28, i.MX35 +and i.MX53 SOCs) only receive RTR frames if the controller is +configured for RX-FIFO mode. + +The RX FIFO mode uses a hardware FIFO with a depth of 6 CAN frames, +while the mailbox mode uses a software FIFO with a depth of up to 62 +CAN frames. With the help of the bigger buffer, the mailbox mode +performs better under high system load situations. + +As reception of RTR frames is part of the CAN standard, all flexcan +cores come up in a mode where RTR reception is possible. + +With the "rx-rtr" private flag the ability to receive RTR frames can +be waived at the expense of losing the ability to receive RTR +messages. This trade off is beneficial in certain use cases. + +"rx-rtr" on + Receive RTR frames. (default) + + The CAN controller can and will receive RTR frames. + + On some IP cores the controller cannot receive RTR frames in the + more performant "RX mailbox" mode and will use "RX FIFO" mode + instead. + +"rx-rtr" off + + Waive ability to receive RTR frames. (not supported on all IP cores) + + This mode activates the "RX mailbox mode" for better performance, on + some IP cores RTR frames cannot be received anymore. + +The setting can only be changed if the interface is down:: + + ip link set dev can0 down + ethtool --set-priv-flags can0 rx-rtr {off|on} + ip link set dev can0 up |