linux-kernel - [PATCH v2] net: mdiobus: Add a function to deassert reset

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Message-ID: <KL1PR01MB54482416A8BE0D80EA27223CE6779@KL1PR01MB5448.apcprd01.prod.exchangelabs.com>
Date:   Wed, 10 May 2023 16:02:52 +0800
From:   Yan Wang <rk.code@...look.com>
To:     andrew@...n.ch
Cc:     Yan Wang <rk.code@...look.com>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Russell King <linux@...linux.org.uk>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        netdev@...r.kernel.org (open list:ETHERNET PHY LIBRARY),
        linux-kernel@...r.kernel.org (open list)
Subject: [PATCH v2] net: mdiobus: Add a function to deassert reset

It is possible to mount multiple sub-devices on the mido bus.
The hardware power-on does not necessarily reset these devices.
The device may be in an uncertain state, causing the device's ID
to be scanned.

So, before adding a reset to the scan, make sure the device is in
normal working mode.

I found that the subsequent drive registers the reset pin into the
structure of the sub-device to prevent conflicts, so release the
reset pin.

Signed-off-by: Yan Wang <rk.code@...look.com>
---
v2:
  - fixed commit message
  - Using gpiod_ replace gpio_
v1: https://lore.kernel.org/all/KL1PR01MB5448631F2D6F71021602117FE6769@KL1PR01MB5448.apcprd01.prod.exchangelabs.com/
  - Incorrect description of commit message.
  - The gpio-api too old
---
 drivers/net/mdio/fwnode_mdio.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/drivers/net/mdio/fwnode_mdio.c b/drivers/net/mdio/fwnode_mdio.c
index 1183ef5e203e..6695848b8ef2 100644
--- a/drivers/net/mdio/fwnode_mdio.c
+++ b/drivers/net/mdio/fwnode_mdio.c
@@ -57,6 +57,20 @@ fwnode_find_mii_timestamper(struct fwnode_handle *fwnode)
 	return register_mii_timestamper(arg.np, arg.args[0]);
 }
 
+static void fwnode_mdiobus_pre_enable_phy(struct fwnode_handle *fwnode)
+{
+	struct gpio_desc *reset;
+
+	reset = fwnode_gpiod_get_index(fwnode, "reset", 0, GPIOD_OUT_HIGH, NULL);
+	if (IS_ERR(reset) && PTR_ERR(reset) != -EPROBE_DEFER)
+		return;
+
+	usleep_range(100, 200);
+	gpiod_set_value_cansleep(reset, 0);
+	/*Release the reset pin,it needs to be registered with the PHY.*/
+	gpiod_put(reset);
+}
+
 int fwnode_mdiobus_phy_device_register(struct mii_bus *mdio,
 				       struct phy_device *phy,
 				       struct fwnode_handle *child, u32 addr)
@@ -119,6 +133,8 @@ int fwnode_mdiobus_register_phy(struct mii_bus *bus,
 	u32 phy_id;
 	int rc;
 
+	fwnode_mdiobus_pre_enable_phy(child);
+
 	psec = fwnode_find_pse_control(child);
 	if (IS_ERR(psec))
 		return PTR_ERR(psec);
-- 
2.17.1