[PATCH v4 2/5] net: lan743x: read SFP straps from PCI11x1x device

[Thangaraj Samynathan <thangaraj.s@microchip.com>]

Reads the SFP enable bits from the strap registers to determine
if the hardware is configured for SFP usage.

Introduce CONFIG_LAN743X_SFP to guard SFP-specific code and select
the required peripheral dependencies (I2C_PCI1XXXX, GP_PCI1XXXX, SFP,
PCS_XPCS) only when SFP hardware is present. HWMON is also selected to
support thermal monitoring of SFP modules via the sfp subsystem.

- Add STRAP_SFP_USE_EN_ and STRAP_SFP_EN_ definitions to read SFP
  straps.
- Store SFP status in the adapter's is_sfp_support_en flag.
- Add a validation check when SFP support is requested without SGMII_EN
  strap; log the invalid combination and force is_sfp_support_en to false
  so subsequent SFP/PCS paths are safely skipped.
- Add debug logging for is_sfp_support_en using str_enable_disable()
  helper, consistent with the existing PCS debug log.

Signed-off-by: Thangaraj Samynathan <thangaraj.s@microchip.com>
---
 drivers/net/ethernet/microchip/Kconfig        | 15 ++++++++++++
 drivers/net/ethernet/microchip/lan743x_main.c | 23 +++++++++++++++++++
 drivers/net/ethernet/microchip/lan743x_main.h |  3 +++
 3 files changed, 41 insertions(+)

diff --git a/drivers/net/ethernet/microchip/Kconfig b/drivers/net/ethernet/microchip/Kconfig
index ee046468652c..0cc55d00ab52 100644
--- a/drivers/net/ethernet/microchip/Kconfig
+++ b/drivers/net/ethernet/microchip/Kconfig
@@ -57,6 +57,21 @@ config LAN743X
 	  To compile this driver as a module, choose M here. The module will be
 	  called lan743x.
 
+config LAN743X_SFP
+	bool "SFP support for PCI11x1x"
+	depends on LAN743X
+	select HWMON if LAN743X=y
+	select I2C_PCI1XXXX
+	select GP_PCI1XXXX
+	select SFP
+	select PCS_XPCS
+	help
+	  Enable SFP module support for the Microchip PCI11x1x Ethernet
+	  controller. Requires the GPIO and I2C peripheral controllers on
+	  the PCI11x1x device to be present and probed.
+
+	  If unsure, say N.
+
 source "drivers/net/ethernet/microchip/lan865x/Kconfig"
 source "drivers/net/ethernet/microchip/lan966x/Kconfig"
 source "drivers/net/ethernet/microchip/sparx5/Kconfig"
diff --git a/drivers/net/ethernet/microchip/lan743x_main.c b/drivers/net/ethernet/microchip/lan743x_main.c
index fad4a246e06e..77a554a0432c 100644
--- a/drivers/net/ethernet/microchip/lan743x_main.c
+++ b/drivers/net/ethernet/microchip/lan743x_main.c
@@ -62,6 +62,14 @@ static void pci11x1x_strap_get_status(struct lan743x_adapter *adapter)
 			adapter->is_pcs_en = true;
 		else
 			adapter->is_pcs_en = false;
+
+#ifdef CONFIG_LAN743X_SFP
+		if ((strap & STRAP_SFP_USE_EN_) && (strap & STRAP_SFP_EN_))
+			adapter->is_sfp_support_en = true;
+		else
+			adapter->is_sfp_support_en = false;
+#endif
+
 	} else {
 		fpga_rev = lan743x_csr_read(adapter, FPGA_REV);
 		if (fpga_rev) {
@@ -73,8 +81,22 @@ static void pci11x1x_strap_get_status(struct lan743x_adapter *adapter)
 			adapter->is_pcs_en = false;
 		}
 	}
+
+#ifdef CONFIG_LAN743X_SFP
+	if (adapter->is_pci11x1x && !adapter->is_pcs_en &&
+	    adapter->is_sfp_support_en) {
+		netif_err(adapter, drv, adapter->netdev,
+			  "Invalid EEPROM configuration: SFP_EN strap specified without SGMII_EN strap\n");
+		adapter->is_sfp_support_en = false;
+	}
+#endif
+
 	netif_dbg(adapter, drv, adapter->netdev,
 		  "PCS I/F %s\n", str_enable_disable(adapter->is_pcs_en));
+#ifdef CONFIG_LAN743X_SFP
+	netif_dbg(adapter, drv, adapter->netdev,
+		  "SFP support %s\n", str_enable_disable(adapter->is_sfp_support_en));
+#endif
 }
 
 static bool is_pci11x1x_chip(struct lan743x_adapter *adapter)
@@ -3665,6 +3687,7 @@ static int lan743x_pcidev_probe(struct pci_dev *pdev,
 			      NETIF_MSG_LINK | NETIF_MSG_IFUP |
 			      NETIF_MSG_IFDOWN | NETIF_MSG_TX_QUEUED;
 	netdev->max_mtu = LAN743X_MAX_FRAME_SIZE;
+	adapter->is_sfp_support_en = false;
 
 	of_get_mac_address(pdev->dev.of_node, adapter->mac_address);
 
diff --git a/drivers/net/ethernet/microchip/lan743x_main.h b/drivers/net/ethernet/microchip/lan743x_main.h
index f0fa0580b04e..d9eb10ffac6c 100644
--- a/drivers/net/ethernet/microchip/lan743x_main.h
+++ b/drivers/net/ethernet/microchip/lan743x_main.h
@@ -37,6 +37,8 @@
 
 #define STRAP_READ			(0x0C)
 #define STRAP_READ_USE_SGMII_EN_	BIT(22)
+#define STRAP_SFP_USE_EN_		BIT(31)
+#define STRAP_SFP_EN_			BIT(15)
 #define STRAP_READ_SGMII_EN_		BIT(6)
 #define STRAP_READ_SGMII_REFCLK_	BIT(5)
 #define STRAP_READ_SGMII_2_5G_		BIT(4)
@@ -1081,6 +1083,7 @@ struct lan743x_adapter {
 	u8			max_tx_channels;
 	u8			used_tx_channels;
 	u8			max_vector_count;
+	bool			is_sfp_support_en;
 
 #define LAN743X_ADAPTER_FLAG_OTP		BIT(0)
 	u32			flags;
-- 
2.34.1