[PATCH net v2 2/2] net: ethernet: oa_tc6: Improvement in buffer overflow handling
From: Selvamani Rajagopal via B4 Relay
Date: Fri Jun 26 2026 - 11:36:23 EST
From: Selvamani Rajagopal <Selvamani.Rajagopal@xxxxxxxxxx>
When oversubscribed traffic causes lot of buffer overflow errors,
probably due to loss of data chunks, driver fails to find a
data chunk with end_valid bit set, before it runs out of sk buffer
space. As a result, assert is seen during skb_put.
Now check is made if tail + len > end, driver abandons the current
data and starts look for a data chunk with start_valid bit,
that is a new frame.
Fixes: d70a0d8f2f2d ("net: ethernet: oa_tc6: implement receive path to receive rx ethernet frames")
Signed-off-by: Selvamani Rajagopal <Selvamani.Rajagopal@xxxxxxxxxx>
---
changes in v2
- Check rx_skb pointer before new allocation and NULL before use.
---
drivers/net/ethernet/oa_tc6.c | 69 +++++++++++++++++++++++++++++++------------
1 file changed, 50 insertions(+), 19 deletions(-)
diff --git a/drivers/net/ethernet/oa_tc6.c b/drivers/net/ethernet/oa_tc6.c
index 3fd4851ee66d..c59daa032e70 100644
--- a/drivers/net/ethernet/oa_tc6.c
+++ b/drivers/net/ethernet/oa_tc6.c
@@ -692,6 +692,12 @@ static void oa_tc6_free_pending_skbs(struct oa_tc6 *tc6)
oa_tc6_cleanup_waiting_tx_skb(tc6);
}
+static void oa_tc6_look_for_new_frame(struct oa_tc6 *tc6)
+{
+ tc6->rx_buf_overflow = true;
+ oa_tc6_cleanup_ongoing_rx_skb(tc6);
+}
+
/* If the failure is at SPI interface level, masking and clearing
* the interrupt of the device won't work. Since SPI interrupt is
* disabled, it should stop the repeated interrupts.
@@ -729,8 +735,7 @@ static int oa_tc6_process_extended_status(struct oa_tc6 *tc6)
}
if (FIELD_GET(STATUS0_RX_BUFFER_OVERFLOW_ERROR, value)) {
- tc6->rx_buf_overflow = true;
- oa_tc6_cleanup_ongoing_rx_skb(tc6);
+ oa_tc6_look_for_new_frame(tc6);
net_err_ratelimited("%s: Receive buffer overflow error\n",
tc6->netdev->name);
return -EAGAIN;
@@ -811,13 +816,35 @@ static void oa_tc6_submit_rx_skb(struct oa_tc6 *tc6)
tc6->rx_skb = NULL;
}
-static void oa_tc6_update_rx_skb(struct oa_tc6 *tc6, u8 *payload, u8 length)
+/* On oversubscribed traffic condition, particularly with overwhelming rx
+ * buffer overflow errors, there could be data chunk loss. If tail + length
+ * goes beyond end pointer, that is an indication that the data chunk with
+ * end_valid bit is lost. Time to look for a data chunk with start_valid bit.
+ *
+ * If rx_skb is NULL, it is time to start looking for data chunk with
+ * start_bit.
+ */
+static int oa_tc6_update_rx_skb(struct oa_tc6 *tc6, u8 *payload, u8 length)
{
+ if (!tc6->rx_skb ||
+ (tc6->rx_skb->tail + length) > tc6->rx_skb->end) {
+ oa_tc6_look_for_new_frame(tc6);
+ return -EAGAIN;
+ }
+
memcpy(skb_put(tc6->rx_skb, length), payload, length);
+ return 0;
}
+/* On overwhelming rx buffer overflow errors, due to data chunk loss, it is
+ * possible that we get two data chunks with start_valid bit set, without
+ * end_valid bit set in between. In this case, rx_skb would have a valid
+ * buffer pointer. We should release, if a valid pointer is found before
+ * allocating a new one.
+ */
static int oa_tc6_allocate_rx_skb(struct oa_tc6 *tc6)
{
+ oa_tc6_cleanup_ongoing_rx_skb(tc6);
tc6->rx_skb = netdev_alloc_skb_ip_align(tc6->netdev, tc6->netdev->mtu +
ETH_HLEN + ETH_FCS_LEN);
if (!tc6->rx_skb) {
@@ -837,7 +864,9 @@ static int oa_tc6_prcs_complete_rx_frame(struct oa_tc6 *tc6, u8 *payload,
if (ret)
return ret;
- oa_tc6_update_rx_skb(tc6, payload, size);
+ ret = oa_tc6_update_rx_skb(tc6, payload, size);
+ if (ret)
+ return ret;
oa_tc6_submit_rx_skb(tc6);
@@ -852,22 +881,24 @@ static int oa_tc6_prcs_rx_frame_start(struct oa_tc6 *tc6, u8 *payload, u16 size)
if (ret)
return ret;
- oa_tc6_update_rx_skb(tc6, payload, size);
-
- return 0;
+ return oa_tc6_update_rx_skb(tc6, payload, size);
}
-static void oa_tc6_prcs_rx_frame_end(struct oa_tc6 *tc6, u8 *payload, u16 size)
+static int oa_tc6_prcs_rx_frame_end(struct oa_tc6 *tc6, u8 *payload, u16 size)
{
- oa_tc6_update_rx_skb(tc6, payload, size);
+ int ret;
- oa_tc6_submit_rx_skb(tc6);
+ ret = oa_tc6_update_rx_skb(tc6, payload, size);
+ if (!ret)
+ oa_tc6_submit_rx_skb(tc6);
+ return ret;
}
-static void oa_tc6_prcs_ongoing_rx_frame(struct oa_tc6 *tc6, u8 *payload,
- u32 footer)
+static int oa_tc6_prcs_ongoing_rx_frame(struct oa_tc6 *tc6, u8 *payload,
+ u32 footer)
{
- oa_tc6_update_rx_skb(tc6, payload, OA_TC6_CHUNK_PAYLOAD_SIZE);
+ return oa_tc6_update_rx_skb(tc6, payload,
+ OA_TC6_CHUNK_PAYLOAD_SIZE);
}
static int oa_tc6_prcs_rx_chunk_payload(struct oa_tc6 *tc6, u8 *data,
@@ -880,6 +911,7 @@ static int oa_tc6_prcs_rx_chunk_payload(struct oa_tc6 *tc6, u8 *data,
bool start_valid = FIELD_GET(OA_TC6_DATA_FOOTER_START_VALID, footer);
bool end_valid = FIELD_GET(OA_TC6_DATA_FOOTER_END_VALID, footer);
u16 size;
+ int ret;
/* Restart the new rx frame after receiving rx buffer overflow error */
if (start_valid && tc6->rx_buf_overflow)
@@ -907,8 +939,7 @@ static int oa_tc6_prcs_rx_chunk_payload(struct oa_tc6 *tc6, u8 *data,
/* Process the chunk with only rx frame end */
if (end_valid && !start_valid) {
size = end_byte_offset + 1;
- oa_tc6_prcs_rx_frame_end(tc6, data, size);
- return 0;
+ return oa_tc6_prcs_rx_frame_end(tc6, data, size);
}
/* Process the chunk with previous rx frame end and next rx frame
@@ -921,7 +952,9 @@ static int oa_tc6_prcs_rx_chunk_payload(struct oa_tc6 *tc6, u8 *data,
*/
if (tc6->rx_skb) {
size = end_byte_offset + 1;
- oa_tc6_prcs_rx_frame_end(tc6, data, size);
+ ret = oa_tc6_prcs_rx_frame_end(tc6, data, size);
+ if (ret)
+ return ret;
}
size = OA_TC6_CHUNK_PAYLOAD_SIZE - start_byte_offset;
return oa_tc6_prcs_rx_frame_start(tc6,
@@ -930,9 +963,7 @@ static int oa_tc6_prcs_rx_chunk_payload(struct oa_tc6 *tc6, u8 *data,
}
/* Process the chunk with ongoing rx frame data */
- oa_tc6_prcs_ongoing_rx_frame(tc6, data, footer);
-
- return 0;
+ return oa_tc6_prcs_ongoing_rx_frame(tc6, data, footer);
}
static u32 oa_tc6_get_rx_chunk_footer(struct oa_tc6 *tc6, u16 footer_offset)
--
2.43.0