4.20-stable review patch. If anyone has any objections, please let me know.
------------------
[ Upstream commit 6571ebce112a21ec9be68ef2f53b96fcd41fd81b ]
If fill_level was not zero and status was not BUSY,
result of "tx_prod - tx_cons - inuse" might be zero.
Subtracting 1 unconditionally results invalid negative return value
on this case.
Make sure not to return an negative value.
Signed-off-by: Tomonori Sakita <tomonori.sakita@xxxxxxxxxx>
Signed-off-by: Atsushi Nemoto <atsushi.nemoto@xxxxxxxxxx>
Reviewed-by: Dalon L Westergreen <dalon.westergreen@xxxxxxxxxxxxxxx>
Acked-by: Thor Thayer <thor.thayer@xxxxxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
drivers/net/ethernet/altera/altera_msgdma.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/drivers/net/ethernet/altera/altera_msgdma.c b/drivers/net/ethernet/altera/altera_msgdma.c
index 0fb986ba3290..0ae723f75341 100644
--- a/drivers/net/ethernet/altera/altera_msgdma.c
+++ b/drivers/net/ethernet/altera/altera_msgdma.c
@@ -145,7 +145,8 @@ u32 msgdma_tx_completions(struct altera_tse_private *priv)
& 0xffff;
if (inuse) { /* Tx FIFO is not empty */
- ready = priv->tx_prod - priv->tx_cons - inuse - 1;
+ ready = max_t(int,
+ priv->tx_prod - priv->tx_cons - inuse - 1, 0);
} else {
/* Check for buffered last packet */
status = csrrd32(priv->tx_dma_csr, msgdma_csroffs(status));
--
2.19.1
