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mlxsw: spectrum: Add support for PAUSE frames
When a packet ingress the switch it's placed in its assigned priority group (PG) buffer in the port's headroom buffer while it goes through the switch's pipeline. After going through the pipeline - which determines its egress port(s) and traffic class - it's moved to the switch's shared buffer awaiting transmission. However, some packets are not eligible to enter the shared buffer due to exceeded quotas or insufficient space. Marking their associated PGs as lossless will cause the packets to accumulate in the PG buffer. Another reason for packets accumulation are complicated pipelines (e.g. involving a lot of ACLs). To prevent packets from being dropped a user can enable PAUSE frames on the port. This will mark all the active PGs as lossless and set their size according to the maximum delay, as it's not configured by user. +----------------+ + | | | | | | | | | | | | | | | | | | Delay | | | | | | | | | | | | | | | Xon/Xoff threshold +----------------+ + | | | | | | 2 * MTU | | | +----------------+ + The delay (612 [Cells]) was calculated according to worst-case scenario involving maximum MTU and 100m cables. After marking the PGs as lossless the device is configured to respect incoming PAUSE frames (Rx PAUSE) and generate PAUSE frames (Tx PAUSE) according to user's settings. Whenever the port's headroom configuration changes we take into account the PAUSE configuration, so that we correctly set the PG's type (lossy / lossless), size and threshold. This can happen when: a) The port's MTU changes, as it directly affects the PG's size. b) A PG is created following user configuration, by binding a priority to it. Note that the relevant SUPPORTED flags were already mistakenly set by the driver before this commit. Signed-off-by: Ido Schimmel <idosch@mellanox.com> Signed-off-by: Jiri Pirko <jiri@mellanox.com> Signed-off-by: David S. Miller <davem@davemloft.net>
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Ido Schimmel
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David S. Miller
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Apr 6, 2016
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