[PATCH net-next v3 1/3] net: dsa: motorcomm: Isolate all ports during chip setup

[David Yang <mmyangfl@gmail.com>]

Chip setup only blocks unknown unicast and unknown multicast frames,
leaving known multicast and broadcast open, though known multicast
cannot appear while the FDB is still empty.

Isolate every port right after the hardware reset, in preparation for
the isolation refactoring. Note that this only minimizes the window: a
reset always brings the hardware back to a dumb switch, so traffic can
leak before and during it.

Signed-off-by: David Yang <mmyangfl@gmail.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
---
 drivers/net/dsa/motorcomm/chip.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/drivers/net/dsa/motorcomm/chip.c b/drivers/net/dsa/motorcomm/chip.c
index 33e5fc127244..e1fa82c6db95 100644
--- a/drivers/net/dsa/motorcomm/chip.c
+++ b/drivers/net/dsa/motorcomm/chip.c
@@ -2221,6 +2221,7 @@ static int yt921x_chip_reset(struct yt921x_priv *priv)
 {
 	struct device *dev = yt921x_priv_to_device(priv);
 	u16 eth_p_tag;
+	u32 ctrl;
 	u32 val;
 	int res;
 
@@ -2258,6 +2259,17 @@ static int yt921x_chip_reset(struct yt921x_priv *priv)
 		return -EINVAL;
 	}
 
+	/* Block all traffic as soon as we reset the hardware since it now acts
+	 * as a dumb switch.
+	 */
+	for (int port = 0; port < YT921X_PORT_NUM; port++) {
+		ctrl = ~(u32)0;
+		res = yt921x_reg_write(priv, YT921X_PORTn_ISOLATION(port),
+				       ctrl);
+		if (res)
+			return res;
+	}
+
 	return 0;
 }
 
-- 
2.53.0