[RFC net-next PATCH 10/13] net: macb: Support external PCSs

[Sean Anderson <sean.anderson@linux.dev>]

This adds support for external PCSs. For example, the Xilinx UltraScale+
processor exposes its GMII interface to the FPGA fabric. This fabric may
implement PCS to convert GMII to a serial interface such as SGMII or
1000BASE-X. When present, the external PCS takes precedence over the
internal PCSs.

Signed-off-by: Sean Anderson <sean.anderson@linux.dev>
---

 drivers/net/ethernet/cadence/macb.h      |  1 +
 drivers/net/ethernet/cadence/macb_main.c | 30 ++++++++++++++++++++----
 2 files changed, 27 insertions(+), 4 deletions(-)

diff --git a/drivers/net/ethernet/cadence/macb.h b/drivers/net/ethernet/cadence/macb.h
index c9a5c8beb2fa..9d310814f052 100644
--- a/drivers/net/ethernet/cadence/macb.h
+++ b/drivers/net/ethernet/cadence/macb.h
@@ -1291,6 +1291,7 @@ struct macb {
 	struct phylink_config	phylink_config;
 	struct phylink_pcs	phylink_usx_pcs;
 	struct phylink_pcs	phylink_sgmii_pcs;
+	struct phylink_pcs	*phylink_ext_pcs;
 
 	u32			caps;
 	unsigned int		dma_burst_length;
diff --git a/drivers/net/ethernet/cadence/macb_main.c b/drivers/net/ethernet/cadence/macb_main.c
index 665fc3c4d39a..65cdf3b478fc 100644
--- a/drivers/net/ethernet/cadence/macb_main.c
+++ b/drivers/net/ethernet/cadence/macb_main.c
@@ -21,6 +21,7 @@
 #include <linux/netdevice.h>
 #include <linux/etherdevice.h>
 #include <linux/dma-mapping.h>
+#include <linux/pcs.h>
 #include <linux/platform_device.h>
 #include <linux/phylink.h>
 #include <linux/of.h>
@@ -549,12 +550,12 @@ static void macb_set_tx_clk(struct macb *bp, int speed)
 		netdev_err(bp->dev, "adjusting tx_clk failed.\n");
 }
 
-static void macb_pcs_get_state(struct phylink_pcs *pcs,
+static void macb_pcs_get_state(struct phylink_pcs *pcs, unsigned int neg_mode,
 			       struct phylink_link_state *state)
 {
 	struct macb *bp = container_of(pcs, struct macb, phylink_sgmii_pcs);
 
-	phylink_mii_c22_pcs_decode_state(state, gem_readl(bp, PCSSTS),
+	phylink_mii_c22_pcs_decode_state(state, neg_mode, gem_readl(bp, PCSSTS),
 					 gem_readl(bp, PCSANLPBASE));
 }
 
@@ -707,7 +708,10 @@ static struct phylink_pcs *macb_mac_select_pcs(struct phylink_config *config,
 	struct net_device *ndev = to_net_dev(config->dev);
 	struct macb *bp = netdev_priv(ndev);
 
-	if (interface == PHY_INTERFACE_MODE_10GBASER)
+	if (bp->phylink_ext_pcs &&
+	    test_bit(interface, bp->phylink_ext_pcs->supported_interfaces))
+		return bp->phylink_ext_pcs;
+	else if (interface == PHY_INTERFACE_MODE_10GBASER)
 		return &bp->phylink_usx_pcs;
 	else if (interface == PHY_INTERFACE_MODE_SGMII)
 		return &bp->phylink_sgmii_pcs;
@@ -733,7 +737,10 @@ static void macb_mac_config(struct phylink_config *config, unsigned int mode,
 		if (state->interface == PHY_INTERFACE_MODE_RMII)
 			ctrl |= MACB_BIT(RM9200_RMII);
 	} else if (macb_is_gem(bp)) {
-		if (macb_mac_select_pcs(config, state->interface))
+		struct phylink_pcs *pcs = macb_mac_select_pcs(config,
+							      state->interface);
+
+		if (pcs && pcs != bp->phylink_ext_pcs)
 			ctrl |= GEM_BIT(PCSSEL);
 		else
 			ctrl &= ~GEM_BIT(PCSSEL);
@@ -907,6 +914,14 @@ static int macb_mii_probe(struct net_device *dev)
 	bp->phylink_sgmii_pcs.ops = &macb_phylink_pcs_ops;
 	bp->phylink_usx_pcs.ops = &macb_phylink_usx_pcs_ops;
 
+	bp->phylink_ext_pcs = pcs_get_by_fwnode_optional(&bp->pdev->dev,
+							 bp->pdev->dev.fwnode,
+							 NULL);
+	if (IS_ERR(bp->phylink_ext_pcs))
+		return dev_err_probe(&bp->pdev->dev,
+				     PTR_ERR(bp->phylink_ext_pcs),
+				     "Could not get external PCS\n");
+
 	bp->phylink_config.dev = &dev->dev;
 	bp->phylink_config.type = PHYLINK_NETDEV;
 	bp->phylink_config.mac_managed_pm = true;
@@ -924,6 +939,11 @@ static int macb_mii_probe(struct net_device *dev)
 	__set_bit(PHY_INTERFACE_MODE_RMII,
 		  bp->phylink_config.supported_interfaces);
 
+	if (bp->phylink_ext_pcs)
+		phy_interface_or(bp->phylink_config.supported_interfaces,
+				 bp->phylink_config.supported_interfaces,
+				 bp->phylink_ext_pcs->supported_interfaces);
+
 	/* Determine what modes are supported */
 	if (macb_is_gem(bp) && (bp->caps & MACB_CAPS_GIGABIT_MODE_AVAILABLE)) {
 		bp->phylink_config.mac_capabilities |= MAC_1000FD;
@@ -950,6 +970,7 @@ static int macb_mii_probe(struct net_device *dev)
 	if (IS_ERR(bp->phylink)) {
 		netdev_err(dev, "Could not create a phylink instance (%ld)\n",
 			   PTR_ERR(bp->phylink));
+		pcs_put(&bp->pdev->dev, bp->phylink_ext_pcs);
 		return PTR_ERR(bp->phylink);
 	}
 
@@ -5462,6 +5483,7 @@ static void macb_remove(struct platform_device *pdev)
 					  bp->rx_clk, bp->tsu_clk);
 			pm_runtime_set_suspended(&pdev->dev);
 		}
+		pcs_put(&pdev->dev, bp->phylink_ext_pcs);
 		phylink_destroy(bp->phylink);
 		free_netdev(dev);
 	}
-- 
2.35.1.1320.gc452695387.dirty