linux-kernel - [PATCH 1/2] ethtool: transceiver reset and presence pin control

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Message-ID: <20250407123714.21646-1-mpazdan@arista.com>
Date: Mon,  7 Apr 2025 12:35:37 +0000
From: Marek Pazdan <mpazdan@...sta.com>
To: linux-kernel@...r.kernel.org,
	netdev@...r.kernel.org,
	intel-wired-lan@...ts.osuosl.org
Cc: Tony Nguyen <anthony.l.nguyen@...el.com>,
	Przemek Kitszel <przemyslaw.kitszel@...el.com>,
	Andrew Lunn <andrew+netdev@...n.ch>,
	"David S . Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>,
	Simon Horman <horms@...nel.org>,
	Kory Maincent <kory.maincent@...tlin.com>,
	Willem de Bruijn <willemb@...gle.com>,
	Alexander Lobakin <aleksander.lobakin@...el.com>,
	Mina Almasry <almasrymina@...gle.com>,
	Edward Cree <ecree.xilinx@...il.com>,
	Daniel Zahka <daniel.zahka@...il.com>,
	Jianbo Liu <jianbol@...dia.com>,
	Gal Pressman <gal@...dia.com>,
	Marek Pazdan <mpazdan@...sta.com>
Subject: [PATCH 1/2] ethtool: transceiver reset and presence pin control

Signal Definition section (Other signals) of SFF-8636 Spec mentions that
additional signals like reset and module present may be implemented for
a specific hardware. There is currently no user space API for control of
those signals so user space management applications have no chance to
perform some diagnostic or configuration operations. This patch uses
get_phy_tunable/set_phy_tunable ioctl API to provide above control to
user space. Despite ethtool reset option seems to be more suitable for
transceiver module reset control, ethtool reset doesn't allow for reset
pin assertion and deassertion. Userspace API may require control over
when pin will be asserte and deasserted so we cannot trigger reset and
leave it to the driver when deassert should be perfromed.

Signed-off-by: Marek Pazdan <mpazdan@...sta.com>
---
 include/uapi/linux/ethtool.h | 14 ++++++++++++++
 net/ethtool/common.c         |  1 +
 net/ethtool/ioctl.c          |  1 +
 3 files changed, 16 insertions(+)

diff --git a/include/uapi/linux/ethtool.h b/include/uapi/linux/ethtool.h
index 84833cca29fe..36c363b0ddd4 100644
--- a/include/uapi/linux/ethtool.h
+++ b/include/uapi/linux/ethtool.h
@@ -289,11 +289,24 @@ struct ethtool_tunable {
 #define ETHTOOL_PHY_EDPD_NO_TX			0xfffe
 #define ETHTOOL_PHY_EDPD_DISABLE		0
 
+/**
+ * SFF-8636 Spec in Signal Definition section (Other signals) mentions
+ * that 'Additional signals such as power, module present, interrupt, reset,
+ * and low-power mode may be implemented'. Below defines reflect present
+ * and reset signal statuses. Additionally ETHTOOL_PHY_MODULE_RESET
+ * in 'enum phy_tunable_id' will be used for reset pin toggle.
+ */
+#define ETHTOOL_PHY_MODULE_RESET_OFF            0x00
+#define ETHTOOL_PHY_MODULE_RESET_ON             0x01
+/* Not Available if module not present */
+#define ETHTOOL_PHY_MODULE_RESET_NA             0xff
+
 enum phy_tunable_id {
 	ETHTOOL_PHY_ID_UNSPEC,
 	ETHTOOL_PHY_DOWNSHIFT,
 	ETHTOOL_PHY_FAST_LINK_DOWN,
 	ETHTOOL_PHY_EDPD,
+	ETHTOOL_PHY_MODULE_RESET,
 	/*
 	 * Add your fresh new phy tunable attribute above and remember to update
 	 * phy_tunable_strings[] in net/ethtool/common.c
diff --git a/net/ethtool/common.c b/net/ethtool/common.c
index 0cb6da1f692a..3d35d3e77348 100644
--- a/net/ethtool/common.c
+++ b/net/ethtool/common.c
@@ -101,6 +101,7 @@ phy_tunable_strings[__ETHTOOL_PHY_TUNABLE_COUNT][ETH_GSTRING_LEN] = {
 	[ETHTOOL_PHY_DOWNSHIFT]	= "phy-downshift",
 	[ETHTOOL_PHY_FAST_LINK_DOWN] = "phy-fast-link-down",
 	[ETHTOOL_PHY_EDPD]	= "phy-energy-detect-power-down",
+	[ETHTOOL_PHY_MODULE_RESET]   = "phy-transceiver-module-reset",
 };
 
 #define __LINK_MODE_NAME(speed, type, duplex) \
diff --git a/net/ethtool/ioctl.c b/net/ethtool/ioctl.c
index 221639407c72..f1f4270cdb69 100644
--- a/net/ethtool/ioctl.c
+++ b/net/ethtool/ioctl.c
@@ -2954,6 +2954,7 @@ static int ethtool_phy_tunable_valid(const struct ethtool_tunable *tuna)
 	switch (tuna->id) {
 	case ETHTOOL_PHY_DOWNSHIFT:
 	case ETHTOOL_PHY_FAST_LINK_DOWN:
+	case ETHTOOL_PHY_MODULE_RESET:
 		if (tuna->len != sizeof(u8) ||
 		    tuna->type_id != ETHTOOL_TUNABLE_U8)
 			return -EINVAL;
-- 
2.47.0