RE: [PATCH net-next] net: phy: micrel: Adding SQI support for lan8814 phy

Hi Michael,

-----Original Message-----
From: Michael Walle <redacted>
Sent: Friday, August 26, 2022 2:13 PM
To: Divya Koppera - I30481 <redacted>
Cc: UNGLinuxDriver <UNGLinuxDriver@microchip.com>; andrew@lunn.ch;
davem@davemloft.net; edumazet@google.com; hkallweit1@gmail.com;
kuba@kernel.org; linux-kernel@vger.kernel.org; linux@armlinux.org.uk;
netdev@vger.kernel.org; pabeni@redhat.com; Michael Walle
[off-list ref]
Subject: Re: [PATCH net-next] net: phy: micrel: Adding SQI support for
lan8814 phy

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Hi,

quoted

Supports SQI(Signal Quality Index) for lan8814 phy, where it has SQI
index of 0-7 values and this indicator can be used for cable integrity
diagnostic and investigating other noise sources.

Signed-off-by: Divya Koppera <redacted>
---
 drivers/net/phy/micrel.c | 35 +++++++++++++++++++++++++++++++++++
 1 file changed, 35 insertions(+)

diff --git a/drivers/net/phy/micrel.c b/drivers/net/phy/micrel.c index

e78d0bf69bc3..3775da7afc64 100644

--- a/drivers/net/phy/micrel.c
+++ b/drivers/net/phy/micrel.c

@@ -1975,6 +1975,13 @@ static int ksz886x_cable_test_get_status(struct

phy_device *phydev,

quoted

 #define LAN8814_CLOCK_MANAGEMENT                     0xd
 #define LAN8814_LINK_QUALITY                         0x8e

+#define LAN8814_DCQ_CTRL                             0xe6
+#define LAN8814_DCQ_CTRL_READ_CAPTURE_                       BIT(15)

Why does it end with an underscore?

All LAN8814 Macros that carries bit numbers are ending with _ in this driver. So following same.

quoted

+#define LAN8814_DCQ_CTRL_CHANNEL_MASK                        GENMASK(1,

0)

quoted

+#define LAN8814_DCQ_SQI                                      0xe4
+#define LAN8814_DCQ_SQI_MAX                          7
+#define LAN8814_DCQ_SQI_VAL_MASK                     GENMASK(3, 1)
+
 static int lanphy_read_page_reg(struct phy_device *phydev, int page,
u32 addr)  {
      int data;

@@ -2927,6 +2934,32 @@ static int lan8814_probe(struct phy_device

*phydev)

quoted

      return 0;
 }

+static int lan8814_get_sqi(struct phy_device *phydev) {
+     int rc, val;
+
+     val = lanphy_read_page_reg(phydev, 1, LAN8814_DCQ_CTRL);
+     if (val < 0)
+             return val;
+
+     val &= ~LAN8814_DCQ_CTRL_CHANNEL_MASK;

I do have a datasheet for this PHY, but it doesn't mention 0xe6 on EP1.

This register values are present in GPHY hard macro as below

4.2.225	DCQ Control Register
Index (In Decimal):	EP 1.230	Size:	16 bits

Can you give me the name of the datasheet which you are following, so that I'll check and let you know the reason.

So I can only guess that this "channel mask" is for the 4 rx/tx pairs on GbE?

Yes channel mask is for wire pair.

And you only seem to evaluate one of them. Is that the correct thing to do
here?

I found in below link is that, get_SQI returns sqi value for 100 base-t1 phy's
https://lore.kernel.org/netdev/20200519075200.24631-2-o.rempel@pengutronix.de/T/ (local)

In lan8814 phy only channel 0 is used for 100base-tx. So returning SQI value for channel 0.

-michael

quoted

+     val |= LAN8814_DCQ_CTRL_READ_CAPTURE_;
+     rc = lanphy_write_page_reg(phydev, 1, LAN8814_DCQ_CTRL, val);
+     if (rc < 0)
+             return rc;
+
+     rc = lanphy_read_page_reg(phydev, 1, LAN8814_DCQ_SQI);
+     if (rc < 0)
+             return rc;
+
+     return FIELD_GET(LAN8814_DCQ_SQI_VAL_MASK, rc); }