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>
---
v2 -> v3
Addressed below review comment
- Replaced hard-coded values with ARRAY_SIZE(rawtable).
---
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 | 155 +++++++++++++++++++++++++++++++++
 1 file changed, 155 insertions(+)

diff --git a/drivers/net/phy/microchip_t1.c b/drivers/net/phy/microchip_t1.c
index 5732ad65e7f9..29ab45b919dc 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 +1435,144 @@ 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 = ARRAY_SIZE(rawtable) / 5;
+	     i < ARRAY_SIZE(rawtable) / 5 * 4; 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 +1621,8 @@ 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 = ARRAY_SIZE(rawtable) / 5;
> +	     i < ARRAY_SIZE(rawtable) / 5 * 4; i++)
> +		sqiavg += rawtable[i];
> +
> +	/* Get SQI average */
> +	sqiavg /= 120;

120?

Isn't that ARRAY_SIZE(rawtable) / 5 * 4 - ARRAY_SIZE(rawtable) / 5 

Please think about the comments being given. I said you should not
assume 200, but use ARRAY_SIZE, so it is possible to change the size
of the array and not get buffer overruns etc. So you need to review
all the code.

Better still, change it to 50 and make sure you get sensible values
from it. The accuracy won't be as good, but i would expect it to be
still about right. But with the current code, i guess you get 7 no
matter what the actual quality is.

This is a general principle in C code, and coding in general. Don't
scatter the same knowledge repeatedly everywhere, because it makes it
error prone to change. You have to find and change them all, rather
than just one central value.

    Andrew

---
pw-bot: cr