This is a note to let you know that I've just added the patch titled net: dsa: felix: fix min gate len calculation for tc when its first gate is closed to the 5.18-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: net-dsa-felix-fix-min-gate-len-calculation-for-tc-when-its-first-gate-is-closed.patch and it can be found in the queue-5.18 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 7e4babffa6f340a74c820d44d44d16511e666424 Mon Sep 17 00:00:00 2001 From: Vladimir Oltean <vladimir.oltean@xxxxxxx> Date: Thu, 4 Aug 2022 23:28:17 +0300 Subject: net: dsa: felix: fix min gate len calculation for tc when its first gate is closed From: Vladimir Oltean <vladimir.oltean@xxxxxxx> commit 7e4babffa6f340a74c820d44d44d16511e666424 upstream. 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: 55a515b1f5a9 ("net: dsa: felix: drop oversized frames with tc-taprio instead of hanging the port") Signed-off-by: Vladimir Oltean <vladimir.oltean@xxxxxxx> Link: https://lore.kernel.org/r/20220804202817.1677572-1-vladimir.oltean@xxxxxxx Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- drivers/net/dsa/ocelot/felix_vsc9959.c | 15 ++++++++++++++- 1 file changed, 14 insertions(+), 1 deletion(-) --- a/drivers/net/dsa/ocelot/felix_vsc9959.c +++ b/drivers/net/dsa/ocelot/felix_vsc9959.c @@ -1133,6 +1133,7 @@ static void vsc9959_tas_min_gate_lengths { struct tc_taprio_sched_entry *entry; u64 gate_len[OCELOT_NUM_TC]; + u8 gates_ever_opened = 0; int tc, i, n; /* Initialize arrays */ @@ -1160,16 +1161,28 @@ static void vsc9959_tas_min_gate_lengths for (tc = 0; tc < OCELOT_NUM_TC; tc++) { if (entry->gate_mask & BIT(tc)) { gate_len[tc] += entry->interval; + gates_ever_opened |= BIT(tc); } else { /* Gate closes now, record a potential new * minimum and reinitialize length */ - if (min_gate_len[tc] > gate_len[tc]) + if (min_gate_len[tc] > gate_len[tc] && + gate_len[tc]) min_gate_len[tc] = gate_len[tc]; gate_len[tc] = 0; } } } + + /* min_gate_len[tc] actually tracks minimum *open* gate time, so for + * permanently closed gates, min_gate_len[tc] will still be U64_MAX. + * Therefore they are currently indistinguishable from permanently + * open gates. Overwrite the gate len with 0 when we know they're + * actually permanently closed, i.e. after the loop above. + */ + for (tc = 0; tc < OCELOT_NUM_TC; tc++) + if (!(gates_ever_opened & BIT(tc))) + min_gate_len[tc] = 0; } /* Update QSYS_PORT_MAX_SDU to make sure the static guard bands added by the Patches currently in stable-queue which might be from vladimir.oltean@xxxxxxx are queue-5.18/net-dsa-felix-keep-reference-on-entire-tc-taprio-con.patch queue-5.18/net-dsa-felix-drop-oversized-frames-with-tc-taprio-i.patch queue-5.18/net-mscc-ocelot-delete-ocelot_port-xmit_template.patch queue-5.18/net-dsa-felix-fix-min-gate-len-calculation-for-tc-when-its-first-gate-is-closed.patch queue-5.18/net-dsa-felix-build-as-module-when-tc-taprio-is-modu.patch queue-5.18/net-mscc-ocelot-minimize-holes-in-struct-ocelot_port.patch queue-5.18/net-sched-provide-shim-definitions-for-taprio_offloa.patch