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
