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

[Horatiu Vultur <horatiu.vultur@microchip.com>]

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@microchip.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@vger.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