[PATCH net 8/8] net: bcmgenet: mask DMA_TIMEOUT_MASK when reading DMA_RING0_TIMEOUT

[Florian Fainelli <florian.fainelli@broadcom.com>]

bcmgenet_get_coalesce() reads DMA_RING0_TIMEOUT to calculate
rx_coalesce_usecs without masking out bits outside DMA_TIMEOUT_MASK
(16 bits). If upper bits are non-zero or contain status/flags, the
computed value of rx_coalesce_usecs returned to userspace via ethtool
becomes corrupted.

Mask the register read with DMA_TIMEOUT_MASK before computing the
timeout in microseconds.

Fixes: 4a29645bfe6c ("net: bcmgenet: Implement RX coalescing control knobs")
Assisted-by: LLM
Co-authored-by: Cursor <cursoragent@cursor.com>
Change-Id: I4c5b5019e764dbd0c7e51bd8c7365939a4736e44
---
 drivers/net/ethernet/broadcom/genet/bcmgenet.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/broadcom/genet/bcmgenet.c b/drivers/net/ethernet/broadcom/genet/bcmgenet.c
index 3a6a2f075959..b15e64a484b4 100644
--- a/drivers/net/ethernet/broadcom/genet/bcmgenet.c
+++ b/drivers/net/ethernet/broadcom/genet/bcmgenet.c
@@ -852,7 +852,8 @@ static int bcmgenet_get_coalesce(struct net_device *dev,
 	ec->rx_max_coalesced_frames =
 		bcmgenet_rdma_ring_readl(priv, 0, DMA_MBUF_DONE_THRESH);
 	ec->rx_coalesce_usecs =
-		bcmgenet_rdma_readl(priv, DMA_RING0_TIMEOUT) * 8192 / 1000;
+		(bcmgenet_rdma_readl(priv, DMA_RING0_TIMEOUT) &
+		 DMA_TIMEOUT_MASK) * 8192 / 1000;
 
 	for (i = 0; i <= priv->hw_params->rx_queues; i++) {
 		ring = &priv->rx_rings[i];
-- 
2.34.1