[PATCH net v2] net: bcmgenet: if UMAC was suspended in SW_RESET, restore it to SW_RESET

When the revised suspend/resume sequence was introduced this led to an edge
case where the TX is left disabled in the following sequence.

1. phy link is down, so UMAC is held in reset and then network interface
   is WoL enabled
2. Enter suspend, bcmgenet_wol_power_down_cfg() enables UMAC_RX since MAC
   is in SW_RESET
4. Enter resume, UMAC_RX is left enabled. Since we only enable UMAC_TX
   and UMAC_RX in SW_RESET. The UMAC_TX is never enabled again on link up.

Fixes: 254f3239dd07 ("net: bcmgenet: revise suspend/resume")
Signed-off-by: Justin Chen <justin.chen@broadcom.com>
Reviewed-by: Florian Fainelli <florian.fainelli@broadcom.com>
Reviewed-by: Nicolai Buchwitz <nb@tipi-net.de>
---
v2
	- Dropped fixes tag that did not introduce the bug

 drivers/net/ethernet/broadcom/genet/bcmgenet_wol.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/drivers/net/ethernet/broadcom/genet/bcmgenet_wol.c b/drivers/net/ethernet/broadcom/genet/bcmgenet_wol.c
index 96d5d4f7f51f..984432952963 100644
--- a/drivers/net/ethernet/broadcom/genet/bcmgenet_wol.c
+++ b/drivers/net/ethernet/broadcom/genet/bcmgenet_wol.c

@@ -253,6 +253,17 @@ int bcmgenet_wol_power_up_cfg(struct bcmgenet_priv *priv,
 	reg = bcmgenet_umac_readl(priv, UMAC_CMD);
 	reg &= ~CMD_CRC_FWD;
 	bcmgenet_umac_writel(priv, reg, UMAC_CMD);
+
+	/*
+	 * Mirror wol_power_down_cfg(). If only UMAC_RX
+	 * is enabled, then we must place the UMAC back
+	 * into SW_RESET.
+	 */
+	reg = bcmgenet_umac_readl(priv, UMAC_CMD);
+	if ((reg & CMD_RX_EN) && !(reg & CMD_TX_EN)) {
+		reg |= CMD_SW_RESET;
+		bcmgenet_umac_writel(priv, reg, UMAC_CMD);
+	}
 	spin_unlock_bh(&priv->reg_lock);
 
 	/* Resume link status tracking */

-- 
2.34.1