[PATCH net-next v2] net: dlink: enable RMON MMIO access on supported devices

[Moon Yeounsu <yyyynoom@gmail.com>]

Enable memory-mapped I/O access to RMON statistics registers for devices
known to work correctly. Currently, only the D-Link DGE-550T (`0x4000`)
with PCI revision A3 (`0x0c`) is allowed.

To support this selectively, a runtime check was added, and the
`MEM_MAPPING` macro was removed in favor of runtime detection.

Tested-on: D-Link DGE-550T Rev-A3
Signed-off-by: Moon Yeounsu <yyyynoom@gmail.com>
---
Changelog:
v1: https://lore.kernel.org/netdev/20250519214046.47856-2-yyyynoom@gmail.com/
v2:
- Remove Kconfig option and do runtime check.
---
 drivers/net/ethernet/dlink/dl2k.c | 57 ++++++++++++++++---------------
 drivers/net/ethernet/dlink/dl2k.h |  2 ++
 2 files changed, 32 insertions(+), 27 deletions(-)

diff --git a/drivers/net/ethernet/dlink/dl2k.c b/drivers/net/ethernet/dlink/dl2k.c
index 232e839a9d07..4e8da21042d5 100644
--- a/drivers/net/ethernet/dlink/dl2k.c
+++ b/drivers/net/ethernet/dlink/dl2k.c
@@ -99,6 +99,13 @@ static const struct net_device_ops netdev_ops = {
 	.ndo_tx_timeout		= rio_tx_timeout,
 };
 
+static bool is_support_rmon_mmio(struct pci_dev *pdev)
+{
+	return pdev->vendor == PCI_VENDOR_ID_DLINK &&
+	       pdev->device == 0x4000 &&
+	       pdev->revision == 0x0c;
+}
+
 static int
 rio_probe1 (struct pci_dev *pdev, const struct pci_device_id *ent)
 {
@@ -131,18 +138,22 @@ rio_probe1 (struct pci_dev *pdev, const struct pci_device_id *ent)
 
 	np = netdev_priv(dev);
 
+	if (is_support_rmon_mmio(pdev))
+		np->rmon_enable = true;
+
 	/* IO registers range. */
 	ioaddr = pci_iomap(pdev, 0, 0);
 	if (!ioaddr)
 		goto err_out_dev;
 	np->eeprom_addr = ioaddr;
 
-#ifdef MEM_MAPPING
-	/* MM registers range. */
-	ioaddr = pci_iomap(pdev, 1, 0);
-	if (!ioaddr)
-		goto err_out_iounmap;
-#endif
+	if (np->rmon_enable) {
+		/* MM registers range. */
+		ioaddr = pci_iomap(pdev, 1, 0);
+		if (!ioaddr)
+			goto err_out_iounmap;
+	}
+
 	np->ioaddr = ioaddr;
 	np->chip_id = chip_idx;
 	np->pdev = pdev;
@@ -287,9 +298,8 @@ rio_probe1 (struct pci_dev *pdev, const struct pci_device_id *ent)
 	dma_free_coherent(&pdev->dev, TX_TOTAL_SIZE, np->tx_ring,
 			  np->tx_ring_dma);
 err_out_iounmap:
-#ifdef MEM_MAPPING
-	pci_iounmap(pdev, np->ioaddr);
-#endif
+	if (np->rmon_enable)
+		pci_iounmap(pdev, np->ioaddr);
 	pci_iounmap(pdev, np->eeprom_addr);
 err_out_dev:
 	free_netdev (dev);
@@ -576,7 +586,8 @@ static void rio_hw_init(struct net_device *dev)
 	dw8(TxDMAPollPeriod, 0xff);
 	dw8(RxDMABurstThresh, 0x30);
 	dw8(RxDMAUrgentThresh, 0x30);
-	dw32(RmonStatMask, 0x0007ffff);
+	if (!np->rmon_enable)
+		dw32(RmonStatMask, 0x0007ffff);
 	/* clear statistics */
 	clear_stats (dev);
 
@@ -1069,9 +1080,6 @@ get_stats (struct net_device *dev)
 {
 	struct netdev_private *np = netdev_priv(dev);
 	void __iomem *ioaddr = np->ioaddr;
-#ifdef MEM_MAPPING
-	int i;
-#endif
 	unsigned int stat_reg;
 
 	/* All statistics registers need to be acknowledged,
@@ -1114,10 +1122,10 @@ get_stats (struct net_device *dev)
 	dr16(MacControlFramesXmtd);
 	dr16(FramesWEXDeferal);
 
-#ifdef MEM_MAPPING
-	for (i = 0x100; i <= 0x150; i += 4)
-		dr32(i);
-#endif
+	if (np->rmon_enable)
+		for (int i = 0x100; i <= 0x150; i += 4)
+			dr32(i);
+
 	dr16(TxJumboFrames);
 	dr16(RxJumboFrames);
 	dr16(TCPCheckSumErrors);
@@ -1131,9 +1139,6 @@ clear_stats (struct net_device *dev)
 {
 	struct netdev_private *np = netdev_priv(dev);
 	void __iomem *ioaddr = np->ioaddr;
-#ifdef MEM_MAPPING
-	int i;
-#endif
 
 	/* All statistics registers need to be acknowledged,
 	   else statistic overflow could cause problems */
@@ -1169,10 +1174,9 @@ clear_stats (struct net_device *dev)
 	dr16(BcstFramesXmtdOk);
 	dr16(MacControlFramesXmtd);
 	dr16(FramesWEXDeferal);
-#ifdef MEM_MAPPING
-	for (i = 0x100; i <= 0x150; i += 4)
-		dr32(i);
-#endif
+	if (np->rmon_enable)
+		for (int i = 0x100; i <= 0x150; i += 4)
+			dr32(i);
 	dr16(TxJumboFrames);
 	dr16(RxJumboFrames);
 	dr16(TCPCheckSumErrors);
@@ -1798,9 +1802,8 @@ rio_remove1 (struct pci_dev *pdev)
 				  np->rx_ring_dma);
 		dma_free_coherent(&pdev->dev, TX_TOTAL_SIZE, np->tx_ring,
 				  np->tx_ring_dma);
-#ifdef MEM_MAPPING
-		pci_iounmap(pdev, np->ioaddr);
-#endif
+		if (np->rmon_enable)
+			pci_iounmap(pdev, np->ioaddr);
 		pci_iounmap(pdev, np->eeprom_addr);
 		free_netdev (dev);
 		pci_release_regions (pdev);
diff --git a/drivers/net/ethernet/dlink/dl2k.h b/drivers/net/ethernet/dlink/dl2k.h
index 0e33e2eaae96..93f2978e8014 100644
--- a/drivers/net/ethernet/dlink/dl2k.h
+++ b/drivers/net/ethernet/dlink/dl2k.h
@@ -401,6 +401,8 @@ struct netdev_private {
 	u16 negotiate;		/* Negotiated media */
 	int phy_addr;		/* PHY addresses. */
 	u16 led_mode;		/* LED mode read from EEPROM (IP1000A only) */
+
+	bool rmon_enable;
 };
 
 /* The station address location in the EEPROM. */
-- 
2.49.0