[PATCH 1/4] ethtool: implement Energy Detect Powerdown support via phy-tunable

[Alexandru Ardelean]

The `phy_tunable_id` has been named `ETHTOOL_PHY_EDPD` since it looks like
this feature is common across other PHYs (like EEE), and defining
`ETHTOOL_PHY_ENERGY_DETECT_POWER_DOWN` seems too long.

The way EDPD works, is that the RX block is put to a lower power mode,
except for link-pulse detection circuits. The TX block is also put to low
power mode, but the PHY wakes-up periodically to send link pulses, to avoid
lock-ups in case the other side is also in EDPD mode.

Currently, there are 2 PHY drivers that look like they could use this new
PHY tunable feature: the `adin` && `micrel` PHYs.

The ADIN's datasheet mentions that TX pulses are at intervals of 1 second
default each, and they can be disabled. For the Micrel KSZ9031 PHY, the
datasheet does not mention whether they can be disabled, but mentions that
they can modified.

The way this change is structured, is similar to the PHY tunable downshift
control:
* a `ETHTOOL_PHY_EDPD_DFLT_TX_INTERVAL` value is exposed to cover a default
  TX interval; some PHYs could specify a certain value that makes sense
* `ETHTOOL_PHY_EDPD_NO_TX` would disable TX when EDPD is enabled
* `ETHTOOL_PHY_EDPD_DISABLE` will disable EDPD

This should allow PHYs to:
* enable EDPD and not enable TX pulses (interval would be 0)
* enable EDPD and configure TX pulse interval; note that TX interval units
  would be PHY specific; we could consider `seconds` as units, but it could
  happen that some PHYs would be prefer 500 milliseconds as a unit;
  a maximum of 32766 units should be sufficient
* disable EDPD

Signed-off-by: Alexandru Ardelean <alexandru.ardelean@xxxxxxxxxx>
---
 include/uapi/linux/ethtool.h | 5 +++++
 net/core/ethtool.c           | 6 ++++++
 2 files changed, 11 insertions(+)

diff --git a/include/uapi/linux/ethtool.h b/include/uapi/linux/ethtool.h
index dd06302aa93e..0349e9c4350f 100644
--- a/include/uapi/linux/ethtool.h
+++ b/include/uapi/linux/ethtool.h
@@ -259,10 +259,15 @@ struct ethtool_tunable {
 #define ETHTOOL_PHY_FAST_LINK_DOWN_ON	0
 #define ETHTOOL_PHY_FAST_LINK_DOWN_OFF	0xff
 
+#define ETHTOOL_PHY_EDPD_DFLT_TX_INTERVAL	0x7fff
+#define ETHTOOL_PHY_EDPD_NO_TX			0x8000
+#define ETHTOOL_PHY_EDPD_DISABLE		0
+
 enum phy_tunable_id {
 	ETHTOOL_PHY_ID_UNSPEC,
 	ETHTOOL_PHY_DOWNSHIFT,
 	ETHTOOL_PHY_FAST_LINK_DOWN,
+	ETHTOOL_PHY_EDPD,
 	/*
 	 * Add your fresh new phy tunable attribute above and remember to update
 	 * phy_tunable_strings[] in net/core/ethtool.c
diff --git a/net/core/ethtool.c b/net/core/ethtool.c
index 6288e69e94fc..c763106c73fc 100644
--- a/net/core/ethtool.c
+++ b/net/core/ethtool.c
@@ -133,6 +133,7 @@ phy_tunable_strings[__ETHTOOL_PHY_TUNABLE_COUNT][ETH_GSTRING_LEN] = {
 	[ETHTOOL_ID_UNSPEC]     = "Unspec",
 	[ETHTOOL_PHY_DOWNSHIFT]	= "phy-downshift",
 	[ETHTOOL_PHY_FAST_LINK_DOWN] = "phy-fast-link-down",
+	[ETHTOOL_PHY_EDPD]	= "phy-energy-detect-power-down",
 };
 
 static int ethtool_get_features(struct net_device *dev, void __user *useraddr)
@@ -2451,6 +2452,11 @@ static int ethtool_phy_tunable_valid(const struct ethtool_tunable *tuna)
 		    tuna->type_id != ETHTOOL_TUNABLE_U8)
 			return -EINVAL;
 		break;
+	case ETHTOOL_PHY_EDPD:
+		if (tuna->len != sizeof(u16) ||
+		    tuna->type_id != ETHTOOL_TUNABLE_U16)
+			return -EINVAL;
+		break;
 	default:
 		return -EINVAL;
 	}
-- 
2.20.1