[PATCH RFC net-next 1/7] net: stmmac: add BASE-X support to integrated PCS

["Russell King (Oracle)" <rmk+kernel@armlinux.org.uk>]

The integrated PCS supports 802.3z (BASE-X) modes when the Synopsys
IP is coupled with an appropriate SerDes to provide the electrical
interface. The PCS presents a TBI interface to the SerDes for this.
Thus, the BASE-X related registers are only present when TBI mode is
supported.

dwmac-qcom-ethqos added support for using 2.5G with the integrated PCS
by calling dwmac_ctrl_ane() directly.

Add support for the following to the integrated PCS:
- 1000BASE-X protocol unconditionally.
- 2500BASE-X if the coupled SerDes supports 2.5G speed.
- The above without autonegotiation.
- If the PCS supports TBI, then optional BASE-X autonegotiation for each
  of the above.

Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
---
 .../net/ethernet/stmicro/stmmac/stmmac_pcs.c  | 96 ++++++++++++++++++-
 .../net/ethernet/stmicro/stmmac/stmmac_pcs.h  |  1 +
 include/linux/stmmac.h                        |  1 +
 3 files changed, 95 insertions(+), 3 deletions(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_pcs.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_pcs.c
index 88fa359ea716..e606dfb85f94 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_pcs.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_pcs.c
@@ -16,6 +16,27 @@
 #define GMAC_ANE_LPA	0x0c	/* ANE link partener ability */
 #define GMAC_TBI	0x14	/* TBI extend status */
 
+static unsigned int dwmac_integrated_pcs_inband_caps(struct phylink_pcs *pcs,
+						     phy_interface_t interface)
+{
+	struct stmmac_pcs *spcs = phylink_pcs_to_stmmac_pcs(pcs);
+	unsigned int ib_caps;
+
+	if (phy_interface_mode_is_8023z(interface)) {
+		ib_caps = LINK_INBAND_DISABLE;
+
+		/* If the PCS supports TBI/RTBI, then BASE-X negotiation is
+		 * supported.
+		 */
+		if (spcs->support_tbi_rtbi)
+			ib_caps |= LINK_INBAND_ENABLE;
+
+		return ib_caps;
+	}
+
+	return 0;
+}
+
 static int dwmac_integrated_pcs_enable(struct phylink_pcs *pcs)
 {
 	struct stmmac_pcs *spcs = phylink_pcs_to_stmmac_pcs(pcs);
@@ -36,7 +57,39 @@ static void dwmac_integrated_pcs_get_state(struct phylink_pcs *pcs,
 					   unsigned int neg_mode,
 					   struct phylink_link_state *state)
 {
-	state->link = false;
+	struct stmmac_pcs *spcs = phylink_pcs_to_stmmac_pcs(pcs);
+	u32 status, lpa;
+
+	status = readl(spcs->base + GMAC_AN_STATUS);
+
+	if (phy_interface_mode_is_8023z(state->interface)) {
+		/* For BASE-X modes, the PCS block supports the advertisement
+		 * and link partner advertisement registers using standard
+		 * 802.3 format. The status register also has the link status
+		 * and AN complete bits in the same bit location. This will
+		 * only be used when AN is enabled.
+		 */
+		lpa = readl(spcs->base + GMAC_ANE_LPA);
+
+		phylink_mii_c22_pcs_decode_state(state, neg_mode, status, lpa);
+	} else {
+		state->link = false;
+	}
+}
+
+static int dwmac_integrated_pcs_config_aneg(struct stmmac_pcs *spcs,
+					    phy_interface_t interface,
+					    const unsigned long *advertising)
+{
+	bool changed = false;
+	u32 adv;
+
+	adv = phylink_mii_c22_pcs_encode_advertisement(interface, advertising);
+	if (readl(spcs->base + GMAC_ANE_ADV) != adv)
+		changed = true;
+	writel(adv, spcs->base + GMAC_ANE_ADV);
+
+	return changed;
 }
 
 static int dwmac_integrated_pcs_config(struct phylink_pcs *pcs,
@@ -46,13 +99,28 @@ static int dwmac_integrated_pcs_config(struct phylink_pcs *pcs,
 				       bool permit_pause_to_mac)
 {
 	struct stmmac_pcs *spcs = phylink_pcs_to_stmmac_pcs(pcs);
+	bool changed = false, ane = true;
+
+	/* Only configure the advertisement and allow AN in BASE-X mode if
+	 * the core supports TBI/RTBI. AN will be filtered out by via phylink
+	 * and the .pcs_inband_caps() method above.
+	 */
+	if (phy_interface_mode_is_8023z(interface) &&
+	    spcs->support_tbi_rtbi) {
+		ane = neg_mode == PHYLINK_PCS_NEG_INBAND_ENABLED;
+
+		changed = dwmac_integrated_pcs_config_aneg(spcs, interface,
+							   advertising);
+	}
 
-	dwmac_ctrl_ane(spcs->base, 0, 1, spcs->priv->hw->reverse_sgmii_enable);
+	dwmac_ctrl_ane(spcs->base, 0, ane,
+		       spcs->priv->hw->reverse_sgmii_enable);
 
-	return 0;
+	return changed;
 }
 
 static const struct phylink_pcs_ops dwmac_integrated_pcs_ops = {
+	.pcs_inband_caps = dwmac_integrated_pcs_inband_caps,
 	.pcs_enable = dwmac_integrated_pcs_enable,
 	.pcs_disable = dwmac_integrated_pcs_disable,
 	.pcs_get_state = dwmac_integrated_pcs_get_state,
@@ -84,9 +152,18 @@ void stmmac_integrated_pcs_irq(struct stmmac_priv *priv, u32 status,
 int stmmac_integrated_pcs_get_phy_intf_sel(struct phylink_pcs *pcs,
 					   phy_interface_t interface)
 {
+	struct stmmac_pcs *spcs = phylink_pcs_to_stmmac_pcs(pcs);
+
 	if (interface == PHY_INTERFACE_MODE_SGMII)
 		return PHY_INTF_SEL_SGMII;
 
+	if (phy_interface_mode_is_8023z(interface)) {
+		if (spcs->support_tbi_rtbi)
+			return PHY_INTF_SEL_TBI;
+		else
+			return PHY_INTF_SEL_SGMII;
+	}
+
 	return -EINVAL;
 }
 
@@ -104,7 +181,20 @@ int stmmac_integrated_pcs_init(struct stmmac_priv *priv, unsigned int offset,
 	spcs->int_mask = int_mask;
 	spcs->pcs.ops = &dwmac_integrated_pcs_ops;
 
+	/* If the PCS supports extended status, then it supports BASE-X AN
+	 * with a TBI interface to the SerDes. Otherwise, we can support
+	 * BASE-X without AN using SGMII, which is required for qcom-ethqos.
+	 */
+	if (readl(spcs->base + GMAC_AN_STATUS) & BMSR_ESTATEN)
+		spcs->support_tbi_rtbi = true;
+
 	__set_bit(PHY_INTERFACE_MODE_SGMII, spcs->pcs.supported_interfaces);
+	__set_bit(PHY_INTERFACE_MODE_1000BASEX, spcs->pcs.supported_interfaces);
+
+	/* Only allow 2500BASE-X if the SerDes has support. */
+	if (priv->plat->flags & STMMAC_FLAG_SERDES_SUPPORTS_2500M)
+		__set_bit(PHY_INTERFACE_MODE_2500BASEX,
+			  spcs->pcs.supported_interfaces);
 
 	priv->integrated_pcs = spcs;
 
diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_pcs.h b/drivers/net/ethernet/stmicro/stmmac/stmmac_pcs.h
index 23bbd4f10bf8..12ea87792fcb 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_pcs.h
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_pcs.h
@@ -32,6 +32,7 @@ struct stmmac_pcs {
 	void __iomem *base;
 	u32 int_mask;
 	struct phylink_pcs pcs;
+	bool support_tbi_rtbi;
 };
 
 static inline struct stmmac_pcs *
diff --git a/include/linux/stmmac.h b/include/linux/stmmac.h
index b96ae9dadfab..aa57ee327606 100644
--- a/include/linux/stmmac.h
+++ b/include/linux/stmmac.h
@@ -192,6 +192,7 @@ enum dwmac_core_type {
 #define STMMAC_FLAG_EN_TX_LPI_CLK_PHY_CAP	BIT(12)
 #define STMMAC_FLAG_HWTSTAMP_CORRECT_LATENCY	BIT(13)
 #define STMMAC_FLAG_KEEP_PREAMBLE_BEFORE_SFD	BIT(14)
+#define STMMAC_FLAG_SERDES_SUPPORTS_2500M	BIT(15)
 
 struct mac_device_info;
 
-- 
2.47.3