diff options
| -rw-r--r-- | drivers/net/dsa/ocelot/felix_vsc9959.c | 35 |
1 files changed, 31 insertions, 4 deletions
diff --git a/drivers/net/dsa/ocelot/felix_vsc9959.c b/drivers/net/dsa/ocelot/felix_vsc9959.c index 1cdce8a98d1d..262be2cf4e4b 100644 --- a/drivers/net/dsa/ocelot/felix_vsc9959.c +++ b/drivers/net/dsa/ocelot/felix_vsc9959.c @@ -22,6 +22,7 @@ #define VSC9959_NUM_PORTS 6 #define VSC9959_TAS_GCL_ENTRY_MAX 63 +#define VSC9959_TAS_MIN_GATE_LEN_NS 33 #define VSC9959_VCAP_POLICER_BASE 63 #define VSC9959_VCAP_POLICER_MAX 383 #define VSC9959_SWITCH_PCI_BAR 4 @@ -1478,6 +1479,23 @@ static void vsc9959_mdio_bus_free(struct ocelot *ocelot) mdiobus_free(felix->imdio); } +/* The switch considers any frame (regardless of size) as eligible for + * transmission if the traffic class gate is open for at least 33 ns. + * Overruns are prevented by cropping an interval at the end of the gate time + * slot for which egress scheduling is blocked, but we need to still keep 33 ns + * available for one packet to be transmitted, otherwise the port tc will hang. + * This function returns the size of a gate interval that remains available for + * setting the guard band, after reserving the space for one egress frame. + */ +static u64 vsc9959_tas_remaining_gate_len_ps(u64 gate_len_ns) +{ + /* Gate always open */ + if (gate_len_ns == U64_MAX) + return U64_MAX; + + return (gate_len_ns - VSC9959_TAS_MIN_GATE_LEN_NS) * PSEC_PER_NSEC; +} + /* Extract shortest continuous gate open intervals in ns for each traffic class * of a cyclic tc-taprio schedule. If a gate is always open, the duration is * considered U64_MAX. If the gate is always closed, it is considered 0. @@ -1596,10 +1614,13 @@ static void vsc9959_tas_guard_bands_update(struct ocelot *ocelot, int port) vsc9959_tas_min_gate_lengths(ocelot_port->taprio, min_gate_len); for (tc = 0; tc < OCELOT_NUM_TC; tc++) { + u64 remaining_gate_len_ps; u32 max_sdu; - if (min_gate_len[tc] == U64_MAX /* Gate always open */ || - min_gate_len[tc] * PSEC_PER_NSEC > needed_bit_time_ps) { + remaining_gate_len_ps = + vsc9959_tas_remaining_gate_len_ps(min_gate_len[tc]); + + if (remaining_gate_len_ps > needed_bit_time_ps) { /* Setting QMAXSDU_CFG to 0 disables oversized frame * dropping. */ @@ -1612,9 +1633,15 @@ static void vsc9959_tas_guard_bands_update(struct ocelot *ocelot, int port) /* If traffic class doesn't support a full MTU sized * frame, make sure to enable oversize frame dropping * for frames larger than the smallest that would fit. + * + * However, the exact same register, QSYS_QMAXSDU_CFG_*, + * controls not only oversized frame dropping, but also + * per-tc static guard band lengths, so it reduces the + * useful gate interval length. Therefore, be careful + * to calculate a guard band (and therefore max_sdu) + * that still leaves 33 ns available in the time slot. */ - max_sdu = div_u64(min_gate_len[tc] * PSEC_PER_NSEC, - picos_per_byte); + max_sdu = div_u64(remaining_gate_len_ps, picos_per_byte); /* A TC gate may be completely closed, which is a * special case where all packets are oversized. * Any limit smaller than 64 octets accomplishes this |