Hello,

On 04/06/2024 22:49, Woojung.Huh@microchip.com wrote:

Hi Enguerrand,

Can you help me to understand your setup? I could see you are using
  - Host CPU : i.MX6ULL
  - DSA Switch : KSZ9897R (https://www.microchip.com/en-us/product/ksz9897)
  - Host-to-KSZ interface : RGMII for data path & SPI for control
Based on this, CPU port is either GMAC6 or GMAC7 (Figure 2-1 of [1])

I have two questions for you.
1. PHY on CPU port
    Which GMAC (or port number) is connected between Host CPU and KSZ9897R?
    If CPU port is either GMAC6 or GMAC7, it is just a MAC-to-MAC connection over RGMII.

I'm using port number 6 as the CPU port for KSZ9897R. GMAC6 is directly 
connected to the MAC of i.MX6ULL (driver is i.MX fec). I'm using RMII 
since gigabit is not supported by the i.MX6ULL.

2. PHY ID
    Its PHY ID is different when checking datasheet of KSZ9897 and KSZ8081.
    PHY ID of Port 1-5 of KSZ9897 is 0x0022-0x1631 per [1]
    PHY ID of KSZ8081 is 0x0022-0x0156x per [2]

That's true for port 1-5, however, I found out that the phy_id emitted 
by GMAC6 is 0x00221561. It is the same as KSZ8081-revA3 according to the 
datasheet. I also studied all registers at runtime for a reliable 
difference to implement something like ksz8051_ksz8795_match_phy_device 
between GMAC6 and KSZ8081, but none appeared to me. Following 
suggestions by Andrew Lunn, I added this virtual phy_id (0x002217ff) to 
hardcode in the devicetree. I'm happy with this solution.

Beside patch, you can create a ticket to Microchip site (https://microchipsupport.force.com/s/supportservice)
if you think it is easier to solve your problem.

I created a joined ticket for tracking (Case number 01457279).

Thank you very much for your time,

Enguerrand de Ribaucourt

Best regards,
Woojung

[1] https://ww1.microchip.com/downloads/aemDocuments/documents/OTH/ProductDocuments/DataSheets/KSZ9897R-Data-Sheet-DS00002330D.pdf
[2] https://www.microchip.com/en-us/product/ksz8081#document-table

quoted

-----Original Message-----
From: Enguerrand de Ribaucourt <enguerrand.de-
ribaucourt@savoirfairelinux.com>
Sent: Tuesday, June 4, 2024 5:23 AM
To: netdev@vger.kernel.org
Cc: andrew@lunn.ch; hkallweit1@gmail.com; linux@armlinux.org.uk; Woojung Huh
- C21699 [off-list ref]; UNGLinuxDriver
[off-list ref]; horms@kernel.org; Tristram Ha - C24268
[off-list ref]; Arun Ramadoss - I17769
[off-list ref]; Enguerrand de Ribaucourt <enguerrand.de-
ribaucourt@savoirfairelinux.com>
Subject: [PATCH net v5 1/4] net: phy: micrel: add Microchip KSZ 9897 Switch
PHY support

EXTERNAL EMAIL: Do not click links or open attachments unless you know the
content is safe

There is a DSA driver for microchip,ksz9897 which can be controlled
through SPI or I2C. This patch adds support for it's CPU ports PHYs to
also allow network access to the switch's CPU port.

The CPU ports PHYs of the KSZ9897 are not documented in the datasheet.
They weirdly use the same PHY ID as the KSZ8081, which is a different
PHY and that driver isn't compatible with KSZ9897. Before this patch,
the KSZ8081 driver was used for the CPU ports of the KSZ9897 but the
link would never come up.

A new driver for the KSZ9897 is added, based on the compatible KSZ87XX.
I could not test if Gigabit Ethernet works, but the link comes up and
can successfully allow packets to be sent and received with DSA tags.

To resolve the KSZ8081/KSZ9897 phy_id conflicts, I could not find any
stable register to distinguish them. Instead of a match_phy_device() ,
I've declared a virtual phy_id with the highest value in Microchip's OUI
range.

Example usage in the device tree:
         compatible = "ethernet-phy-id0022.17ff";

A discussion to find better alternatives had been opened with the
Microchip team, with no response yet.

See https://lore.kernel.org/all/20220207174532.362781-1-enguerrand.de-
ribaucourt@savoirfairelinux.com/

Fixes: b987e98e50ab ("dsa: add DSA switch driver for Microchip KSZ9477")
Signed-off-by: Enguerrand de Ribaucourt <enguerrand.de-
ribaucourt@savoirfairelinux.com>
---
v5:
  - rewrap comments
  - restore suspend/resume for KSZ9897
v4: https://lore.kernel.org/all/20240531142430.678198-2-enguerrand.de-
ribaucourt@savoirfairelinux.com/
  - rebase on net/main
  - add Fixes tag
  - use pseudo phy_id instead of of_tree search
v3: https://lore.kernel.org/all/20240530102436.226189-2-enguerrand.de-
ribaucourt@savoirfairelinux.com/
---
  drivers/net/phy/micrel.c   | 13 ++++++++++++-
  include/linux/micrel_phy.h |  4 ++++
  2 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/drivers/net/phy/micrel.c b/drivers/net/phy/micrel.c
index 8c20cf937530..11e58fc628df 100644
--- a/drivers/net/phy/micrel.c
+++ b/drivers/net/phy/micrel.c

@@ -16,7 +16,7 @@
   *                        ksz8081, ksz8091,
   *                        ksz8061,
   *             Switch : ksz8873, ksz886x
- *                      ksz9477, lan8804
+ *                      ksz9477, ksz9897, lan8804
   */

  #include <linux/bitfield.h>

@@ -5545,6 +5545,16 @@ static struct phy_driver ksphy_driver[] = {
         .suspend        = genphy_suspend,
         .resume         = ksz9477_resume,
         .get_features   = ksz9477_get_features,
+}, {
+       .phy_id         = PHY_ID_KSZ9897,
+       .phy_id_mask    = MICREL_PHY_ID_MASK,
+       .name           = "Microchip KSZ9897 Switch",
+       /* PHY_BASIC_FEATURES */
+       .config_init    = kszphy_config_init,
+       .config_aneg    = ksz8873mll_config_aneg,
+       .read_status    = ksz8873mll_read_status,
+       .suspend        = genphy_suspend,
+       .resume         = genphy_resume,
  } };

  module_phy_driver(ksphy_driver);

@@ -5570,6 +5580,7 @@ static struct mdio_device_id __maybe_unused

micrel_tbl[] = {
         { PHY_ID_LAN8814, MICREL_PHY_ID_MASK },
         { PHY_ID_LAN8804, MICREL_PHY_ID_MASK },
         { PHY_ID_LAN8841, MICREL_PHY_ID_MASK },
+       { PHY_ID_KSZ9897, MICREL_PHY_ID_MASK },
         { }
  };

diff --git a/include/linux/micrel_phy.h b/include/linux/micrel_phy.h
index 591bf5b5e8dc..81cc16dc2ddf 100644
--- a/include/linux/micrel_phy.h
+++ b/include/linux/micrel_phy.h

@@ -39,6 +39,10 @@
  #define PHY_ID_KSZ87XX         0x00221550

  #define        PHY_ID_KSZ9477          0x00221631
+/* Pseudo ID to specify in compatible field of device tree.
+ * Otherwise the device reports the same ID as KSZ8081 on CPU ports.
+ */
+#define        PHY_ID_KSZ9897          0x002217ff

  /* struct phy_device dev_flags definitions */
  #define MICREL_PHY_50MHZ_CLK   BIT(0)
--

2.34.1