net: stmmac: dwmac4: extend timeout for VLAN Tag register busy bit check

Increase the timeout for checking the busy bit of the VLAN Tag register
from 10µs to 500ms. This change is necessary to accommodate scenarios
where Energy Efficient Ethernet (EEE) is enabled.

Overnight testing revealed that when EEE is active, the busy bit can
remain set for up to approximately 300ms. The new 500ms timeout provides
a safety margin.

Fixes: ed64639 ("net: stmmac: Add support for VLAN Rx filtering")
Signed-off-by: Shenwei Wang <shenwei.wang@nxp.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: NipaLocal <nipa@local>

drivers/net/ethernet/stmicro/stmmac/dwmac4_core.c

@@ -14,6 +14,7 @@
 #include <linux/slab.h>
 #include <linux/ethtool.h>
 #include <linux/io.h>
+#include <linux/iopoll.h>
 #include "stmmac.h"
 #include "stmmac_pcs.h"
 #include "dwmac4.h"
@@ -471,7 +472,7 @@ static int dwmac4_write_vlan_filter(struct net_device *dev,
 				    u8 index, u32 data)
 {
 	void __iomem *ioaddr = (void __iomem *)dev->base_addr;
-	int i, timeout = 10;
+	int ret, timeout = 500000; //500ms
 	u32 val;
 
 	if (index >= hw->num_vlan)
@@ -487,12 +488,11 @@ static int dwmac4_write_vlan_filter(struct net_device *dev,
 
 	writel(val, ioaddr + GMAC_VLAN_TAG);
 
-	for (i = 0; i < timeout; i++) {
-		val = readl(ioaddr + GMAC_VLAN_TAG);
-		if (!(val & GMAC_VLAN_TAG_CTRL_OB))
-			return 0;
-		udelay(1);
-	}
+	ret = readl_poll_timeout(ioaddr + GMAC_VLAN_TAG, val,
+				 !(val & GMAC_VLAN_TAG_CTRL_OB),
+				 1000, timeout);
+	if (!ret)
+		return 0;
 
 	netdev_err(dev, "Timeout accessing MAC_VLAN_Tag_Filter\n");