[PATCH net-next] net: lan743x: fix SGMII detection on PCI1xxxx B0+ during warm reset

[Thangaraj Samynathan]

A warm reset on boards using an EEPROM-only strap configuration (where
no MAC address is set in the image) can cause the driver to incorrectly
revert to RGMII mode. This occurs because the ENET_CONFIG_LOAD_STARTED
bit may not persist or behave as expected.

Update pci11x1x_strap_get_status() to use revision-specific validation:

- For PCI11x1x A0: Continue using the legacy check (config load started
  or reset protection) to validate the SGMII strap.
- For PCI11x1x B0 and later: Use the newly available
  STRAP_READ_USE_SGMII_EN_ bit in the upper strap register to validate
  the lower SGMII_EN bit.

This ensures the SGMII interface is correctly identified even after a
warm reboot.

Signed-off-by: Thangaraj Samynathan <thangaraj.s@xxxxxxxxxxxxx>
---
 drivers/net/ethernet/microchip/lan743x_main.c | 11 +++++++----
 drivers/net/ethernet/microchip/lan743x_main.h |  1 +
 2 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/drivers/net/ethernet/microchip/lan743x_main.c b/drivers/net/ethernet/microchip/lan743x_main.c
index a3845edf0e48..866f6a3da0d9 100644
--- a/drivers/net/ethernet/microchip/lan743x_main.c
+++ b/drivers/net/ethernet/microchip/lan743x_main.c
@@ -32,10 +32,12 @@ static void pci11x1x_strap_get_status(struct lan743x_adapter *adapter)
 {
 	u32 chip_rev;
 	u32 cfg_load;
+	u32 dev_rev;
 	u32 hw_cfg;
 	u32 strap;
 	int ret;
 
+	dev_rev = adapter->csr.id_rev & ID_REV_CHIP_REV_MASK_;
 	/* Timeout = 100 (i.e. 1 sec (10 msce * 100)) */
 	ret = lan743x_hs_syslock_acquire(adapter, 100);
 	if (ret < 0) {
@@ -47,10 +49,11 @@ static void pci11x1x_strap_get_status(struct lan743x_adapter *adapter)
 	cfg_load = lan743x_csr_read(adapter, ETH_SYS_CONFIG_LOAD_STARTED_REG);
 	lan743x_hs_syslock_release(adapter);
 	hw_cfg = lan743x_csr_read(adapter, HW_CFG);
-
-	if (cfg_load & GEN_SYS_LOAD_STARTED_REG_ETH_ ||
-	    hw_cfg & HW_CFG_RST_PROTECT_) {
-		strap = lan743x_csr_read(adapter, STRAP_READ);
+	strap = lan743x_csr_read(adapter, STRAP_READ);
+	if ((dev_rev == ID_REV_CHIP_REV_PCI11X1X_A0_  &&
+	     (cfg_load & GEN_SYS_LOAD_STARTED_REG_ETH_ ||
+	     hw_cfg & HW_CFG_RST_PROTECT_)) ||
+	     (strap & STRAP_READ_USE_SGMII_EN_)) {
 		if (strap & STRAP_READ_SGMII_EN_)
 			adapter->is_sgmii_en = true;
 		else
diff --git a/drivers/net/ethernet/microchip/lan743x_main.h b/drivers/net/ethernet/microchip/lan743x_main.h
index 02a28b709163..160d94a7cee6 100644
--- a/drivers/net/ethernet/microchip/lan743x_main.h
+++ b/drivers/net/ethernet/microchip/lan743x_main.h
@@ -27,6 +27,7 @@
 #define ID_REV_CHIP_REV_MASK_		(0x0000FFFF)
 #define ID_REV_CHIP_REV_A0_		(0x00000000)
 #define ID_REV_CHIP_REV_B0_		(0x00000010)
+#define ID_REV_CHIP_REV_PCI11X1X_A0_	(0x000000A0)
 #define ID_REV_CHIP_REV_PCI11X1X_B0_	(0x000000B0)
 
 #define FPGA_REV			(0x04)
-- 
2.34.1