[net-next,v2,3/3] net: phy: at803x: Support downstream SFP cage

Commit Message

Robert Hancock Jan. 11, 2022, 9:55 p.m. UTC

Add support for downstream SFP cages for AR8031 and AR8033. This is
primarily intended for fiber modules or direct-attach cables, however
copper modules which work in 1000Base-X mode may also function. Such
modules are allowed with a warning.

Signed-off-by: Robert Hancock <[e-mail]>
---
 drivers/net/phy/at803x.c | 56 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 56 insertions(+)

Comments

Andrew Lunn Jan. 12, 2022, 12:14 a.m. UTC | #1

On Tue, Jan 11, 2022 at 03:55:04PM -0600, Robert Hancock wrote:
> Add support for downstream SFP cages for AR8031 and AR8033. This is
> primarily intended for fiber modules or direct-attach cables, however
> copper modules which work in 1000Base-X mode may also function. Such
> modules are allowed with a warning.

The previous patch added:

AT803X_MODE_CFG_BASET_SGMII

So it seems it has some support for SGMII? Cannot it be used?

   Andrew

Robert Hancock Jan. 12, 2022, 12:24 a.m. UTC | #2

On Wed, 2022-01-12 at 01:14 +0100, Andrew Lunn wrote:
> On Tue, Jan 11, 2022 at 03:55:04PM -0600, Robert Hancock wrote:
> > Add support for downstream SFP cages for AR8031 and AR8033. This is
> > primarily intended for fiber modules or direct-attach cables, however
> > copper modules which work in 1000Base-X mode may also function. Such
> > modules are allowed with a warning.
> 
> The previous patch added:
> 
> AT803X_MODE_CFG_BASET_SGMII
> 
> So it seems it has some support for SGMII? Cannot it be used?

According to Qualcomm, the AR8031 PHY has one SERDES block which can either be
used in SGMII mode on the MAC side, or in 1000Base-X mode on the line side, but
not in SGMII mode on the line side, so only 1000Base-X mode can be used there.
So that means no SGMII support for SFP modules unfortunately.

In practice, it does seem to work with most of the copper modules we have
tried, though in some cases (like where the module defaults to SGMII mode, or
1000Base-X mode with auto-negotiation disabled) we need to disable auto-
negotiation on the interface to get the link to come up (the module still does
its own auto-negotiation on the copper side regardless). Of course without
SGMII, 100 or 10 Mbps speeds won't work.

> 
>    Andrew

Patch

diff --git a/drivers/net/phy/at803x.c b/drivers/net/phy/at803x.c
index 63d84eb2eddb..c4e87c76edcb 100644
--- a/drivers/net/phy/at803x.c
+++ b/drivers/net/phy/at803x.c
@@ -19,6 +19,8 @@ 
 #include <linux/regulator/of_regulator.h>
 #include <linux/regulator/driver.h>
 #include <linux/regulator/consumer.h>
+#include <linux/phylink.h>
+#include <linux/sfp.h>
 #include <dt-bindings/net/qca-ar803x.h>
 
 #define AT803X_SPECIFIC_FUNCTION_CONTROL	0x10
@@ -664,6 +666,55 @@  static int at8031_register_regulators(struct phy_device *phydev)
 	return 0;
 }
 
+static int at803x_sfp_insert(void *upstream, const struct sfp_eeprom_id *id)
+{
+	struct phy_device *phydev = upstream;
+	__ETHTOOL_DECLARE_LINK_MODE_MASK(phy_support);
+	__ETHTOOL_DECLARE_LINK_MODE_MASK(sfp_support);
+	phy_interface_t iface;
+
+	linkmode_zero(phy_support);
+	phylink_set(phy_support, 1000baseX_Full);
+	phylink_set(phy_support, 1000baseT_Full);
+	phylink_set(phy_support, Autoneg);
+	phylink_set(phy_support, Pause);
+	phylink_set(phy_support, Asym_Pause);
+
+	linkmode_zero(sfp_support);
+	sfp_parse_support(phydev->sfp_bus, id, sfp_support);
+	/* Some modules support 10G modes as well as others we support.
+	 * Mask out non-supported modes so the correct interface is picked.
+	 */
+	linkmode_and(sfp_support, phy_support, sfp_support);
+
+	if (linkmode_empty(sfp_support)) {
+		dev_err(&phydev->mdio.dev, "incompatible SFP module inserted\n");
+		return -EINVAL;
+	}
+
+	iface = sfp_select_interface(phydev->sfp_bus, sfp_support);
+
+	/* Only 1000Base-X is supported by AR8031/8033 as the downstream SerDes
+	 * interface for use with SFP modules.
+	 * However, some copper modules detected as having a preferred SGMII
+	 * interface do default to and function in 1000Base-X mode, so just
+	 * print a warning and allow such modules, as they may have some chance
+	 * of working.
+	 */
+	if (iface == PHY_INTERFACE_MODE_SGMII)
+		dev_warn(&phydev->mdio.dev, "module may not function if 1000Base-X not supported\n");
+	else if (iface != PHY_INTERFACE_MODE_1000BASEX)
+		return -EINVAL;
+
+	return 0;
+}
+
+static const struct sfp_upstream_ops at803x_sfp_ops = {
+	.attach = phy_sfp_attach,
+	.detach = phy_sfp_detach,
+	.module_insert = at803x_sfp_insert,
+};
+
 static int at803x_parse_dt(struct phy_device *phydev)
 {
 	struct device_node *node = phydev->mdio.dev.of_node;
@@ -771,6 +822,11 @@  static int at803x_parse_dt(struct phy_device *phydev)
 			phydev_err(phydev, "failed to get VDDIO regulator\n");
 			return PTR_ERR(priv->vddio);
 		}
+
+		/* Only AR8031/8033 support 1000Base-X for SFP modules */
+		ret = phy_sfp_probe(phydev, &at803x_sfp_ops);
+		if (ret < 0)
+			return ret;
 	}
 
 	return 0;