This is a note to let you know that I've just added the patch titled
igc: Fix packet still tx after gate close by reducing i226 MAC retry buffer
to the 6.6-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:
igc-fix-packet-still-tx-after-gate-close-by-reducing.patch
and it can be found in the queue-6.6 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 3a799096cedb22239a468aa2736f08938311db2c
Author: Faizal Rahim <faizal.abdul.rahim@xxxxxxxxxxxxxxx>
Date: Sat Jul 6 11:38:07 2024 -0400
igc: Fix packet still tx after gate close by reducing i226 MAC retry buffer
[ Upstream commit e037a26ead187901f83cad9c503ccece5ff6817a ]
Testing uncovered that even when the taprio gate is closed, some packets
still transmit.
According to i225/6 hardware errata [1], traffic might overflow the
planned QBV window. This happens because MAC maintains an internal buffer,
primarily for supporting half duplex retries. Therefore, even when the
gate closes, residual MAC data in the buffer may still transmit.
To mitigate this for i226, reduce the MAC's internal buffer from 192 bytes
to the recommended 88 bytes by modifying the RETX_CTL register value.
This follows guidelines from:
[1] Ethernet Controller I225/I22 Spec Update Rev 2.1 Errata Item 9:
TSN: Packet Transmission Might Cross Qbv Window
[2] I225/6 SW User Manual Rev 1.2.4: Section 8.11.5 Retry Buffer Control
Note that the RETX_CTL register can't be used in TSN mode because half
duplex feature cannot coexist with TSN.
Test Steps:
1. Send taprio cmd to board A:
tc qdisc replace dev enp1s0 parent root handle 100 taprio \
num_tc 4 \
map 3 2 1 0 3 3 3 3 3 3 3 3 3 3 3 3 \
queues 1@0 1@1 1@2 1@3 \
base-time 0 \
sched-entry S 0x07 500000 \
sched-entry S 0x0f 500000 \
flags 0x2 \
txtime-delay 0
Note that for TC3, gate should open for 500us and close for another
500us.
3. Take tcpdump log on Board B.
4. Send udp packets via UDP tai app from Board A to Board B.
5. Analyze tcpdump log via wireshark log on Board B. Ensure that the
total time from the first to the last packet received during one cycle
for TC3 does not exceed 500us.
Fixes: 43546211738e ("igc: Add new device ID's")
Signed-off-by: Faizal Rahim <faizal.abdul.rahim@xxxxxxxxxxxxxxx>
Acked-by: Vinicius Costa Gomes <vinicius.gomes@xxxxxxxxx>
Tested-by: Mor Bar-Gabay <morx.bar.gabay@xxxxxxxxx>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@xxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/drivers/net/ethernet/intel/igc/igc_defines.h b/drivers/net/ethernet/intel/igc/igc_defines.h
index b3037016f31d2..a18af5c87cde4 100644
--- a/drivers/net/ethernet/intel/igc/igc_defines.h
+++ b/drivers/net/ethernet/intel/igc/igc_defines.h
@@ -402,6 +402,12 @@
#define IGC_DTXMXPKTSZ_TSN 0x19 /* 1600 bytes of max TX DMA packet size */
#define IGC_DTXMXPKTSZ_DEFAULT 0x98 /* 9728-byte Jumbo frames */
+/* Retry Buffer Control */
+#define IGC_RETX_CTL 0x041C
+#define IGC_RETX_CTL_WATERMARK_MASK 0xF
+#define IGC_RETX_CTL_QBVFULLTH_SHIFT 8 /* QBV Retry Buffer Full Threshold */
+#define IGC_RETX_CTL_QBVFULLEN 0x1000 /* Enable QBV Retry Buffer Full Threshold */
+
/* Transmit Scheduling Latency */
/* Latency between transmission scheduling (LaunchTime) and the time
* the packet is transmitted to the network in nanosecond.
diff --git a/drivers/net/ethernet/intel/igc/igc_tsn.c b/drivers/net/ethernet/intel/igc/igc_tsn.c
index 22cefb1eeedfa..46d4c3275bbb5 100644
--- a/drivers/net/ethernet/intel/igc/igc_tsn.c
+++ b/drivers/net/ethernet/intel/igc/igc_tsn.c
@@ -78,6 +78,15 @@ void igc_tsn_adjust_txtime_offset(struct igc_adapter *adapter)
wr32(IGC_GTXOFFSET, txoffset);
}
+static void igc_tsn_restore_retx_default(struct igc_adapter *adapter)
+{
+ struct igc_hw *hw = &adapter->hw;
+ u32 retxctl;
+
+ retxctl = rd32(IGC_RETX_CTL) & IGC_RETX_CTL_WATERMARK_MASK;
+ wr32(IGC_RETX_CTL, retxctl);
+}
+
/* Returns the TSN specific registers to their default values after
* the adapter is reset.
*/
@@ -91,6 +100,9 @@ static int igc_tsn_disable_offload(struct igc_adapter *adapter)
wr32(IGC_TXPBS, I225_TXPBSIZE_DEFAULT);
wr32(IGC_DTXMXPKTSZ, IGC_DTXMXPKTSZ_DEFAULT);
+ if (igc_is_device_id_i226(hw))
+ igc_tsn_restore_retx_default(adapter);
+
tqavctrl = rd32(IGC_TQAVCTRL);
tqavctrl &= ~(IGC_TQAVCTRL_TRANSMIT_MODE_TSN |
IGC_TQAVCTRL_ENHANCED_QAV | IGC_TQAVCTRL_FUTSCDDIS);
@@ -111,6 +123,25 @@ static int igc_tsn_disable_offload(struct igc_adapter *adapter)
return 0;
}
+/* To partially fix i226 HW errata, reduce MAC internal buffering from 192 Bytes
+ * to 88 Bytes by setting RETX_CTL register using the recommendation from:
+ * a) Ethernet Controller I225/I226 Specification Update Rev 2.1
+ * Item 9: TSN: Packet Transmission Might Cross the Qbv Window
+ * b) I225/6 SW User Manual Rev 1.2.4: Section 8.11.5 Retry Buffer Control
+ */
+static void igc_tsn_set_retx_qbvfullthreshold(struct igc_adapter *adapter)
+{
+ struct igc_hw *hw = &adapter->hw;
+ u32 retxctl, watermark;
+
+ retxctl = rd32(IGC_RETX_CTL);
+ watermark = retxctl & IGC_RETX_CTL_WATERMARK_MASK;
+ /* Set QBVFULLTH value using watermark and set QBVFULLEN */
+ retxctl |= (watermark << IGC_RETX_CTL_QBVFULLTH_SHIFT) |
+ IGC_RETX_CTL_QBVFULLEN;
+ wr32(IGC_RETX_CTL, retxctl);
+}
+
static int igc_tsn_enable_offload(struct igc_adapter *adapter)
{
struct igc_hw *hw = &adapter->hw;
@@ -123,6 +154,9 @@ static int igc_tsn_enable_offload(struct igc_adapter *adapter)
wr32(IGC_DTXMXPKTSZ, IGC_DTXMXPKTSZ_TSN);
wr32(IGC_TXPBS, IGC_TXPBSIZE_TSN);
+ if (igc_is_device_id_i226(hw))
+ igc_tsn_set_retx_qbvfullthreshold(adapter);
+
for (i = 0; i < adapter->num_tx_queues; i++) {
struct igc_ring *ring = adapter->tx_ring[i];
u32 txqctl = 0;
