Merge tag 'mlx5e-updates-2018-05-19' of git://git.kernel.org/pub/scm/linux/kernel/git/saeed/linux
Saeed Mahameed says:
====================
mlx5e-updates-2018-05-19
This series contains updates for mlx5e netdevice driver with one subject,
DSCP to priority mapping, in the first patch Huy adds the needed API in
dcbnl, the second patch adds the needed mlx5 core capability bits for the
feature, and all other patches are mlx5e (netdev) only changes to add
support for the feature.
From: Huy Nguyen
Dscp to priority mapping for Ethernet packet:
These patches enable differentiated services code point (dscp) to
priority mapping for Ethernet packet. Once this feature is
enabled, the packet is routed to the corresponding priority based on its
dscp. User can combine this feature with priority flow control (pfc)
feature to have priority flow control based on the dscp.
Firmware interface:
Mellanox firmware provides two control knobs for this feature:
QPTS register allow changing the trust state between dscp and
pcp mode. The default is pcp mode. Once in dscp mode, firmware will
route the packet based on its dscp value if the dscp field exists.
QPDPM register allow mapping a specific dscp (0 to 63) to a
specific priority (0 to 7). By default, all the dscps are mapped to
priority zero.
Software interface:
This feature is controlled via application priority TLV. IEEE
specification P802.1Qcd/D2.1 defines priority selector id 5 for
application priority TLV. This APP TLV selector defines DSCP to priority
map. This APP TLV can be sent by the switch or can be set locally using
software such as lldptool. In mlx5 drivers, we add the support for net
dcb's getapp and setapp call back. Mlx5 driver only handles the selector
id 5 application entry (dscp application priority application entry).
If user sends multiple dscp to priority APP TLV entries on the same
dscp, the last sent one will take effect. All the previous sent will be
deleted.
This attribute combined with pfc attribute allows advanced user to
fine tune the qos setting for specific priority queue. For example,
user can give dedicated buffer for one or more priorities or user
can give large buffer to certain priorities.
The dcb buffer configuration will be controlled by lldptool.
>> lldptool -T -i eth2 -V BUFFER prio 0,2,5,7,1,2,3,6
maps priorities 0,1,2,3,4,5,6,7 to receive buffer 0,2,5,7,1,2,3,6
>> lldptool -T -i eth2 -V BUFFER size 87296,87296,0,87296,0,0,0,0
sets receive buffer size for buffer 0,1,2,3,4,5,6,7 respectively
After discussion on mailing list with Jakub, Jiri, Ido and John, we agreed to
choose dcbnl over devlink interface since this feature is intended to set
port attributes which are governed by the netdev instance of that port, where
devlink API is more suitable for global ASIC configurations.
The firmware trust state (in QPTS register) is changed based on the
number of dscp to priority application entries. When the first dscp to
priority application entry is added by the user, the trust state is
changed to dscp. When the last dscp to priority application entry is
deleted by the user, the trust state is changed to pcp.
When the port is in DSCP trust state, the transmit queue is selected
based on the dscp of the skb.
When the port is in DSCP trust state and vport inline mode is not NONE,
firmware requires mlx5 driver to copy the IP header to the
wqe ethernet segment inline header if the skb has it.
This is done by changing the transmit queue sq's min inline mode to L3.
Note that the min inline mode of sqs that belong to other features
such as xdpsq, icosq are not modified.
====================
Signed-off-by: David S. Miller <davem@davemloft.net>
