netdev - [RFC PATCH net-next 1/2] net: phy: Add phy latency adjustment support in phy framework.

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Date:   Tue, 19 Apr 2022 10:37:03 +0200
From:   Horatiu Vultur <horatiu.vultur@...rochip.com>
To:     <netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>
CC:     <andrew@...n.ch>, <hkallweit1@...il.com>, <linux@...linux.org.uk>,
        <davem@...emloft.net>, <kuba@...nel.org>, <pabeni@...hat.com>,
        <UNGLinuxDriver@...rochip.com>, <richardcochran@...il.com>,
        Horatiu Vultur <horatiu.vultur@...rochip.com>
Subject: [RFC PATCH net-next 1/2] net: phy: Add phy latency adjustment support in phy framework.

Add adjustment support for latency for the phy using sysfs.
This is used to adjust the latency of the phy based on link mode
and direction.

Signed-off-by: Horatiu Vultur <horatiu.vultur@...rochip.com>
---
 .../ABI/testing/sysfs-class-net-phydev        | 10 ++++
 drivers/net/phy/phy_device.c                  | 58 +++++++++++++++++++
 include/linux/phy.h                           |  9 +++
 3 files changed, 77 insertions(+)

diff --git a/Documentation/ABI/testing/sysfs-class-net-phydev b/Documentation/ABI/testing/sysfs-class-net-phydev
index ac722dd5e694..a99bbfeddb6f 100644
--- a/Documentation/ABI/testing/sysfs-class-net-phydev
+++ b/Documentation/ABI/testing/sysfs-class-net-phydev
@@ -63,3 +63,13 @@ Description:
 		only used internally by the kernel and their placement are
 		not meant to be stable across kernel versions. This is intended
 		for facilitating the debugging of PHY drivers.
+
+What:		/sys/class/mdio_bus/<bus>/<device>/adjust_latency
+Date:		April 2022
+KernelVersion:	5.19
+Contact:	netdev@...r.kernel.org
+Description:
+		This file adjusts the latency in the PHY. To set value,
+		write three integers into the file: interface mode, RX latency,
+		TX latency. When the file is read, it returns the supported
+		interface modes and the latency values.
diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
index 8406ac739def..80bf04ca0e02 100644
--- a/drivers/net/phy/phy_device.c
+++ b/drivers/net/phy/phy_device.c
@@ -529,6 +529,48 @@ static ssize_t phy_dev_flags_show(struct device *dev,
 }
 static DEVICE_ATTR_RO(phy_dev_flags);
 
+static ssize_t adjust_latency_show(struct device *dev,
+				   struct device_attribute *attr, char *buf)
+{
+	struct phy_device *phydev = to_phy_device(dev);
+	ssize_t count = 0;
+	int err, i;
+	s32 rx, tx;
+
+	for (i = 0; i < __ETHTOOL_LINK_MODE_MASK_NBITS; ++i) {
+		err = phydev->drv->get_adj_latency(phydev, i, &rx, &tx);
+		if (err == -EINVAL)
+			continue;
+
+		count += sprintf(&buf[count], "%d rx: %d, tx: %d\n", i, rx, tx);
+	}
+
+	return count;
+}
+
+static ssize_t adjust_latency_store(struct device *dev,
+				    struct device_attribute *attr,
+				    const char *buf, size_t count)
+{
+	struct phy_device *phydev = to_phy_device(dev);
+	enum ethtool_link_mode_bit_indices link_mode;
+	int cnt, err = -EINVAL;
+	s32 rx, tx;
+
+	cnt = sscanf(buf, "%u %d %d", &link_mode, &rx, &tx);
+	if (cnt != 3)
+		goto out;
+
+	err = phydev->drv->set_adj_latency(phydev, link_mode, rx, tx);
+	if (err)
+		goto out;
+
+	return count;
+out:
+	return err;
+}
+static DEVICE_ATTR_RW(adjust_latency);
+
 static struct attribute *phy_dev_attrs[] = {
 	&dev_attr_phy_id.attr,
 	&dev_attr_phy_interface.attr,
@@ -3009,6 +3051,16 @@ static int phy_probe(struct device *dev)
 
 	phydev->drv = phydrv;
 
+	if (phydev->drv &&
+	    phydev->drv->set_adj_latency &&
+	    phydev->drv->get_adj_latency) {
+		err = sysfs_create_file(&phydev->mdio.dev.kobj,
+					&dev_attr_adjust_latency.attr);
+		if (err)
+			phydev_err(phydev, "error creating 'adjust_latency' sysfs entry\n");
+		err = 0;
+	}
+
 	/* Disable the interrupt if the PHY doesn't support it
 	 * but the interrupt is still a valid one
 	 */
@@ -3112,6 +3164,12 @@ static int phy_remove(struct device *dev)
 	if (phydev->drv && phydev->drv->remove)
 		phydev->drv->remove(phydev);
 
+	if (phydev->drv &&
+	    phydev->drv->set_adj_latency &&
+	    phydev->drv->get_adj_latency)
+		sysfs_remove_file(&phydev->mdio.dev.kobj,
+				  &dev_attr_adjust_latency.attr);
+
 	/* Assert the reset signal */
 	phy_device_reset(phydev, 1);
 
diff --git a/include/linux/phy.h b/include/linux/phy.h
index 36ca2b5c2253..584e467ff4d1 100644
--- a/include/linux/phy.h
+++ b/include/linux/phy.h
@@ -932,6 +932,15 @@ struct phy_driver {
 	int (*get_sqi)(struct phy_device *dev);
 	/** @get_sqi_max: Get the maximum signal quality indication */
 	int (*get_sqi_max)(struct phy_device *dev);
+	/** @set_adj_latency: Set the latency values of the PHY */
+	int (*set_adj_latency)(struct phy_device *dev,
+			       enum ethtool_link_mode_bit_indices link_mode,
+			       s32 rx, s32 tx);
+	/** @get_latency: Get the latency values of the PHY */
+	int (*get_adj_latency)(struct phy_device *dev,
+			       enum ethtool_link_mode_bit_indices link_mode,
+			       s32 *rx, s32 *tx);
+
 };
 #define to_phy_driver(d) container_of(to_mdio_common_driver(d),		\
 				      struct phy_driver, mdiodrv)
-- 
2.33.0