net: dsa: felix: fix min gate len calculation for tc when its first gate is closed
min_gate_len[tc] is supposed to track the shortest interval of continuously open gates for a traffic class. For example, in the following case: TC 76543210 t0 00000001b 200000 ns t1 00000010b 200000 ns min_gate_len[0] and min_gate_len[1] should be 200000, while min_gate_len[2-7] should be 0. However what happens is that min_gate_len[0] is 200000, but min_gate_len[1] ends up being 0 (despite gate_len[1] being 200000 at the point where the logic detects the gate close event for TC 1). The problem is that the code considers a "gate close" event whenever it sees that there is a 0 for that TC (essentially it's level rather than edge triggered). By doing that, any time a gate is seen as closed without having been open prior, gate_len, which is 0, will be written into min_gate_len. Once min_gate_len becomes 0, it's impossible for it to track anything higher than that (the length of actually open intervals). To fix this, we make the writing to min_gate_len[tc] be edge-triggered, which avoids writes for gates that are closed in consecutive intervals. However what this does is it makes us need to special-case the permanently closed gates at the end. Fixes: 55a515b1 ("net: dsa: felix: drop oversized frames with tc-taprio instead of hanging the port") Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com> Link: https://lore.kernel.org/r/20220804202817.1677572-1-vladimir.oltean@nxp.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>
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