linux-phytec-ti

HACK: drivers: net: cpsw: add broadcast/multicast rate limit support

Add broadcast/multicast rate limit support via switch config ioctl to
limit the number of broadcast/multicast packets processed by ALE.

For CPSW ALE multicast (MC) / broadcast (BC) Rate limit, ENABLE_RATE_LIMIT
bit has to be set in ALE_CONTROL Register.

The MC/BC Rate limit feature expected to limit number of BC/MC packets per
sec which need to be configured as below:

- ale_port.BCASTMCAST/_LIMIT fields and ALE_PRESCALE register have to be
  configured to achieve desired MC/BC Rate limit:

 number_of_packets/sec = (Fclk / ALE_PRESCALE) * port.BCASTMCAST/_LIMIT
 where: ALE_PRESCALE width is 19bit and min value 0x10.

 with Fclk = 125MHz and port.BCASTMCAST/_LIMIT = 1
  max number_of_packets/sec = (125MHz / 0x10) * 1 = 7 812 500
  min number_of_packets/sec = (125MHz / 0xFFFFF) * 1 = 119

above values are more than enough (with higher Fclk they will be just
better), so port.BCASTMCAST/_LIMIT can be selected to be 1 while
ALE_PRESCALE is calculated as:

 ALE_PRESCALE = Fclk / number_of_packets

- RATE_LIMIT_TX bit has to be set in ALE_CONTROL Register to 1 for TX and 0
  for RX

- ENABLE_RATE_LIMIT bit has to be set in ALE_CONTROL Register

This patch implements above logic.

Testing:
 # ifconfig - check "RX packets:X"
 # switch-config --add-multi 01:00:5E:00:00:05 -n 7
 # switch-config -l -n 1 -L 1000 -B 1000
 # on host PC generate BC/MC traffic
  (packeth: gen-b->num_packets=10000
  gen-b->delay=100
 # ifconfig - check "RX packets:X+1000"

TODO:
The patch is marked as a hack because switch-configuration in general
uses some non-standard private ioctls. This needs to be moved to a
standard kernel framework.

Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.com>
Signed-off-by: Mugunthan V N <mugunthanvnm@ti.com>
Signed-off-by: Sekhar Nori <nsekhar@ti.com>