[PATCH v3 0/4] can: c_can: cache frames to operate as a true FIFO

Performance tests of the c_can driver led to the patch that gives the
series its name. I also added two patches not really related to the topic
of the series.

Run test succesfully on a custom board having two CAN ports.
I connected the CAN1 port to the CAN2 port with a cable. Then I
opened two terminals. On one I issued a dump command and on the
other the transmit command used in the tests described in
https://marc.info/?l=linux-can&m=139746476821294&w=2.

Terminal-1:
$ ip link set can1 type can bitrate <bitrate>
$ ip link set up can1
$ candump can1 >/tmp/can-test-<bitrate>

Terminal-2
$ ip link set can0 type can bitrate <bitrate>
$ ip link set up can0
$ time cangen can0 -g0 -p1 -I5A5 -L0 -x -n 1000000

Then I applied the following commands to the file generated by the dump
command:
$ wc -l </tmp/can-test-<bitrate>                                 # ca
$ egrep -v '  can1  5A5   \[0\]' /tmp/can-test-<bitrate> | wc -l # cb

I repeated the tests for 1000000, 500000, 250000 and 125000 bitrates,
before and after applying the series.
Here are the results:

Before applying the series:
 bitrate       time         ca         cb
  125000    6m 42.71s    1000000        0
  250000    3m 23.28s    1000000        0
  500000    1m 44.04s    1000000        0
 1000000    1m  8.44s    1000000        0

After applying ring-FIFO series:
 bitrate       time         ca         cb
  125000    6m 40.48s    1000000        0
  250000    3m 20.80s    1000000        0
  500000    1m 42.56s    1000000        0
 1000000    1m  7.89s    1000000        0


Changes in v3:
- Remove the transmission spin_lock.
- Use IF_RX in c_can_do_tx().

Changes in v2:
- Move c_can_get_tx_free() from c_can_main.c to c_can.h.

Dario Binacchi (4):
  can: c_can: remove struct c_can_priv::priv field
  can: c_can: exit c_can_do_tx() early if no frames have been sent
  can: c_can: support tx ring algorithm
  can: c_can: cache frames to operate as a true FIFO

 drivers/net/can/c_can/c_can.h          | 25 ++++++-
 drivers/net/can/c_can/c_can_main.c     | 95 +++++++++++++++++++-------
 drivers/net/can/c_can/c_can_platform.c |  1 -
 3 files changed, 94 insertions(+), 27 deletions(-)

-- 
2.17.1