When reading buffer descriptors on RX or on TX completion, an
RX_USED/TX_USED bit is checked first to ensure that the descriptor has
been populated. However, there are no memory barriers to ensure that the
data protected by the RX_USED/TX_USED bit is up-to-date with respect to
that bit.
Fix that by adding DMA read memory barriers on those paths.
I did not observe any actual issues caused by these being missing,
though.
Tested on a ZynqMP based system.
Signed-off-by: Anssi Hannula <anssi.hann...@bitwise.fi>
Fixes: 89e5785fc8a6 ("[PATCH] Atmel MACB ethernet driver")
Cc: Nicolas Ferre <nicolas.fe...@microchip.com>
---
drivers/net/ethernet/cadence/macb_main.c | 20 ++++++++++++++++----
1 file changed, 16 insertions(+), 4 deletions(-)
diff --git a/drivers/net/ethernet/cadence/macb_main.c
b/drivers/net/ethernet/cadence/macb_main.c
index 430b7a0f5436..c93baa8621d5 100644
--- a/drivers/net/ethernet/cadence/macb_main.c
+++ b/drivers/net/ethernet/cadence/macb_main.c
@@ -861,6 +861,11 @@ static void macb_tx_interrupt(struct macb_queue *queue)
/* First, update TX stats if needed */
if (skb) {
+ /* Ensure all of desc is at least as up-to-date
+ * as ctrl (TX_USED bit)
+ */
+ dma_rmb();
+
if (gem_ptp_do_txstamp(queue, skb, desc) == 0) {
/* skb now belongs to timestamp buffer
* and will be removed later
@@ -1000,12 +1005,16 @@ static int gem_rx(struct macb_queue *queue, int budget)
rmb();
rxused = (desc->addr & MACB_BIT(RX_USED)) ? true : false;
- addr = macb_get_addr(bp, desc);
- ctrl = desc->ctrl;
if (!rxused)
break;
+ /* Ensure other data is at least as up-to-date as rxused */
+ dma_rmb();
+
+ addr = macb_get_addr(bp, desc);
+ ctrl = desc->ctrl;
+
queue->rx_tail++;
count++;
@@ -1180,11 +1189,14 @@ static int macb_rx(struct macb_queue *queue, int budget)
/* Make hw descriptor updates visible to CPU */
rmb();
- ctrl = desc->ctrl;
-
if (!(desc->addr & MACB_BIT(RX_USED)))
break;
+ /* Ensure other data is at least as up-to-date as addr */
+ dma_rmb();
+
+ ctrl = desc->ctrl;
+
if (ctrl & MACB_BIT(RX_SOF)) {
if (first_frag != -1)
discard_partial_frame(queue, first_frag, tail);
--
2.17.2
