From: Tarun Alle <Tarun.Alle@microchip.com>

Add support for measuring Signal Quality Index for LAN887x T1 PHY.
Signal Quality Index (SQI) is measure of Link Channel Quality from
0 to 7, with 7 as the best. By default, a link loss event shall
indicate an SQI of 0.

Signed-off-by: Tarun Alle <Tarun.Alle@microchip.com>
---
v1->v2
Addressed below review comments
- Replaced hard-coded 200 with ARRAY_SIZE(rawtable).
- Replaced return value -EINVAL with -ENETDOWN.
- Changed link checks.
---
 drivers/net/phy/microchip_t1.c | 154 +++++++++++++++++++++++++++++++++
 1 file changed, 154 insertions(+)

diff --git a/drivers/net/phy/microchip_t1.c b/drivers/net/phy/microchip_t1.c
index 5732ad65e7f9..22a5214acf86 100644
--- a/drivers/net/phy/microchip_t1.c
+++ b/drivers/net/phy/microchip_t1.c
@@ -2,6 +2,7 @@
 // Copyright (C) 2018 Microchip Technology
 
 #include <linux/kernel.h>
+#include <linux/sort.h>
 #include <linux/module.h>
 #include <linux/delay.h>
 #include <linux/mii.h>
@@ -188,6 +189,20 @@
 #define LAN887X_EFUSE_READ_DAT9_SGMII_DIS	BIT(9)
 #define LAN887X_EFUSE_READ_DAT9_MAC_MODE	GENMASK(1, 0)
 
+#define LAN887X_COEFF_PWR_DN_CONFIG_100		0x0404
+#define LAN887X_COEFF_PWR_DN_CONFIG_100_V	0x16d6
+#define LAN887X_SQI_CONFIG_100			0x042e
+#define LAN887X_SQI_CONFIG_100_V		0x9572
+#define LAN887X_SQI_MSE_100			0x483
+
+#define LAN887X_POKE_PEEK_100			0x040d
+#define LAN887X_POKE_PEEK_100_EN		BIT(0)
+
+#define LAN887X_COEFF_MOD_CONFIG		0x080d
+#define LAN887X_COEFF_MOD_CONFIG_DCQ_COEFF_EN	BIT(8)
+
+#define LAN887X_DCQ_SQI_STATUS			0x08b2
+
 #define DRIVER_AUTHOR	"Nisar Sayed <nisar.sayed@microchip.com>"
 #define DRIVER_DESC	"Microchip LAN87XX/LAN937x/LAN887x T1 PHY driver"
 
@@ -1420,6 +1435,143 @@ static void lan887x_get_strings(struct phy_device *phydev, u8 *data)
 		ethtool_puts(&data, lan887x_hw_stats[i].string);
 }
 
+/* Compare block to sort in ascending order */
+static int data_compare(const void *a, const void *b)
+{
+	return  *(u16 *)a - *(u16 *)b;
+}
+
+static int lan887x_get_sqi_100M(struct phy_device *phydev)
+{
+	u16 rawtable[200];
+	u32 sqiavg = 0;
+	u8 sqinum;
+	int rc;
+
+	/* Configuration of SQI 100M */
+	rc = phy_write_mmd(phydev, MDIO_MMD_VEND1,
+			   LAN887X_COEFF_PWR_DN_CONFIG_100,
+			   LAN887X_COEFF_PWR_DN_CONFIG_100_V);
+	if (rc < 0)
+		return rc;
+
+	rc = phy_write_mmd(phydev, MDIO_MMD_VEND1, LAN887X_SQI_CONFIG_100,
+			   LAN887X_SQI_CONFIG_100_V);
+	if (rc < 0)
+		return rc;
+
+	rc = phy_read_mmd(phydev, MDIO_MMD_VEND1, LAN887X_SQI_CONFIG_100);
+	if (rc != LAN887X_SQI_CONFIG_100_V)
+		return -EINVAL;
+
+	rc = phy_modify_mmd(phydev, MDIO_MMD_VEND1, LAN887X_POKE_PEEK_100,
+			    LAN887X_POKE_PEEK_100_EN,
+			    LAN887X_POKE_PEEK_100_EN);
+	if (rc < 0)
+		return rc;
+
+	/* Required before reading register
+	 * otherwise it will return high value
+	 */
+	msleep(50);
+
+	/* Link check before raw readings */
+	rc = genphy_c45_read_link(phydev);
+	if (rc < 0)
+		return rc;
+
+	if (!phydev->link)
+		return -ENETDOWN;
+
+	/* Get 200 SQI raw readings */
+	for (int i = 0; i < ARRAY_SIZE(rawtable); i++) {
+		rc = phy_write_mmd(phydev, MDIO_MMD_VEND1,
+				   LAN887X_POKE_PEEK_100,
+				   LAN887X_POKE_PEEK_100_EN);
+		if (rc < 0)
+			return rc;
+
+		rc = phy_read_mmd(phydev, MDIO_MMD_VEND1,
+				  LAN887X_SQI_MSE_100);
+		if (rc < 0)
+			return rc;
+
+		rawtable[i] = rc;
+	}
+
+	/* Link check after raw readings */
+	rc = genphy_c45_read_link(phydev);
+	if (rc < 0)
+		return rc;
+
+	if (!phydev->link)
+		return -ENETDOWN;
+
+	/* Sort SQI raw readings in ascending order */
+	sort(rawtable, ARRAY_SIZE(rawtable), sizeof(u16), data_compare, NULL);
+
+	/* Keep inliers and discard outliers */
+	for (int i = 40; i < 160; i++)
+		sqiavg += rawtable[i];
+
+	/* Get SQI average */
+	sqiavg /= 120;
+
+	if (sqiavg < 75)
+		sqinum = 7;
+	else if (sqiavg < 94)
+		sqinum = 6;
+	else if (sqiavg < 119)
+		sqinum = 5;
+	else if (sqiavg < 150)
+		sqinum = 4;
+	else if (sqiavg < 189)
+		sqinum = 3;
+	else if (sqiavg < 237)
+		sqinum = 2;
+	else if (sqiavg < 299)
+		sqinum = 1;
+	else
+		sqinum = 0;
+
+	return sqinum;
+}
+
+static int lan887x_get_sqi(struct phy_device *phydev)
+{
+	int rc, val;
+
+	if (phydev->speed != SPEED_1000 &&
+	    phydev->speed != SPEED_100) {
+		return -ENETDOWN;
+	}
+
+	if (phydev->speed == SPEED_100)
+		return lan887x_get_sqi_100M(phydev);
+
+	/* Writing DCQ_COEFF_EN to trigger a SQI read */
+	rc = phy_set_bits_mmd(phydev, MDIO_MMD_VEND1,
+			      LAN887X_COEFF_MOD_CONFIG,
+			      LAN887X_COEFF_MOD_CONFIG_DCQ_COEFF_EN);
+	if (rc < 0)
+		return rc;
+
+	/* Wait for DCQ done */
+	rc = phy_read_mmd_poll_timeout(phydev, MDIO_MMD_VEND1,
+				       LAN887X_COEFF_MOD_CONFIG, val, ((val &
+				       LAN887X_COEFF_MOD_CONFIG_DCQ_COEFF_EN) !=
+				       LAN887X_COEFF_MOD_CONFIG_DCQ_COEFF_EN),
+				       10, 200, true);
+	if (rc < 0)
+		return rc;
+
+	rc = phy_read_mmd(phydev, MDIO_MMD_VEND1, LAN887X_DCQ_SQI_STATUS);
+	if (rc < 0)
+		return rc;
+
+	return FIELD_GET(T1_DCQ_SQI_MSK, rc);
+}
+
 static struct phy_driver microchip_t1_phy_driver[] = {
 	{
 		PHY_ID_MATCH_MODEL(PHY_ID_LAN87XX),
@@ -1468,6 +1620,8 @@ static struct phy_driver microchip_t1_phy_driver[] = {
 		.suspend	= genphy_suspend,
 		.resume		= genphy_resume,
 		.read_status	= genphy_c45_read_status,
+		.get_sqi	= lan887x_get_sqi,
+		.get_sqi_max	= lan87xx_get_sqi_max,
 	}
 };
 
-- 
2.34.1

> +	/* Keep inliers and discard outliers */
> +	for (int i = 40; i < 160; i++)
> +		sqiavg += rawtable[i];

	for (int i = ARRAY_SIZE(rawtable) / 5 ; i < ARRAY_SIZE(rawtable) / 5 * 4; i++) {

You don't want to hard code the size of the array anywhere except for
when actually declaring it. It then becomes easy to change the size of
it.

	Andrew