Re: [PATCH net-next] net: macb: add support for 1000BASE-X autonegotiation to PCS

The current PCS code unconditionally uses SGMII autonegotiation, though
the hardware supports both SGMII and 1000BASE-X modes. Decouple the
choice of PCS enablement from use of the SGMII mode when running at
gigabit rates and announce to phylink that 1000BASE-X is a supported
operating mode. This enables direct attachment of the PCS to e.g. an
SFP.

Tested and developed on Microchip Polarfire SoC hardware.

Signed-off-by: Nathan Whitehorn <redacted>
---
 drivers/net/ethernet/cadence/macb_main.c | 31 ++++++++++++++++++------
 1 file changed, 24 insertions(+), 7 deletions(-)

diff --git a/drivers/net/ethernet/cadence/macb_main.c b/drivers/net/ethernet/cadence/macb_main.c
index d394f1f43b68..284a3b03f8c7 100644
--- a/drivers/net/ethernet/cadence/macb_main.c
+++ b/drivers/net/ethernet/cadence/macb_main.c

@@ -583,7 +583,13 @@ static void macb_pcs_get_state(struct phylink_pcs *pcs, unsigned int neg_mode,
 
 static void macb_pcs_an_restart(struct phylink_pcs *pcs)
 {
-	/* Not supported */
+	struct macb *bp = container_of(pcs, struct macb, phylink_sgmii_pcs);
+	u32 old, new;
+
+	old = gem_readl(bp, PCSCNTRL);
+	new = old | BMCR_ANRESTART;
+	if (old != new)
+		gem_writel(bp, PCSCNTRL, new);

 }
 
 static int macb_pcs_config(struct phylink_pcs *pcs,

@@ -750,7 +756,9 @@ static void macb_mac_config(struct phylink_config *config, unsigned int mode,
 		ctrl &= ~(GEM_BIT(SGMIIEN) | GEM_BIT(PCSSEL));
 		ncr &= ~GEM_BIT(ENABLE_HS_MAC);
 
-		if (state->interface == PHY_INTERFACE_MODE_SGMII) {
+		if (state->interface == PHY_INTERFACE_MODE_1000BASEX) {
+			ctrl |= GEM_BIT(PCSSEL);
+		} else if (state->interface == PHY_INTERFACE_MODE_SGMII) {
 			ctrl |= GEM_BIT(SGMIIEN) | GEM_BIT(PCSSEL);
 		} else if (state->interface == PHY_INTERFACE_MODE_10GBASER) {
 			ctrl |= GEM_BIT(PCSSEL);

@@ -957,7 +965,8 @@ static struct phylink_pcs *macb_mac_select_pcs(struct phylink_config *config,
 
 	if (interface == PHY_INTERFACE_MODE_10GBASER)
 		return &bp->phylink_usx_pcs;
-	else if (interface == PHY_INTERFACE_MODE_SGMII)
+	else if (interface == PHY_INTERFACE_MODE_1000BASEX ||
+	         interface == PHY_INTERFACE_MODE_SGMII)
 		return &bp->phylink_sgmii_pcs;
 	else
 		return NULL;

@@ -1025,13 +1034,15 @@ static int macb_mii_probe(struct net_device *dev)
 	struct macb *bp = netdev_priv(dev);
 
 	bp->phylink_sgmii_pcs.ops = &macb_phylink_pcs_ops;
+	bp->phylink_sgmii_pcs.poll = true;