RE: [PATCH net] net: dsa: microchip: Fix KSZ8863 reset problem

On Fri, Aug 01, 2025 at 05:22:53PM -0700, Tristram.Ha@microchip.com wrote:

quoted

From: Tristram Ha <redacted>

ksz8873_valid_regs[] was added for register access for KSZ8863/KSZ8873
switches, but the reset register is not in the list so
ksz8_reset_switch() does not take any effect.

ksz_cfg() is updated to display an error so that there will be a future
check for adding new register access code.

A side effect of not resetting the switch is the static MAC table is not
cleared.  Further additions to the table will show write error as there
are only 8 entries in the table.

Thank you for fixing it!

quoted

Fixes: d0dec3333040 ("net: dsa: microchip: Add register access control for KSZ8873

chip")

quoted

Signed-off-by: Tristram Ha <redacted>
---
 drivers/net/dsa/microchip/ksz8.c       | 7 ++++++-
 drivers/net/dsa/microchip/ksz_common.c | 1 +
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/net/dsa/microchip/ksz8.c b/drivers/net/dsa/microchip/ksz8.c
index 76e490070e9c..6d282a8e3684 100644
--- a/drivers/net/dsa/microchip/ksz8.c
+++ b/drivers/net/dsa/microchip/ksz8.c

@@ -36,7 +36,12 @@

 static void ksz_cfg(struct ksz_device *dev, u32 addr, u8 bits, bool set)
 {
-     regmap_update_bits(ksz_regmap_8(dev), addr, bits, set ? bits : 0);
+     int ret;
+
+     ret = regmap_update_bits(ksz_regmap_8(dev), addr, bits, set ? bits : 0);
+     if (ret)
+             dev_err(dev->dev, "can't update reg 0x%x: %pe\n", addr,
+                     ERR_PTR(ret));

Better using ksz_rmw8() instead. It is already providing error message.

In this file there is 4 direct accesses to regmap_update_bits() without
error handling. It would be great if you have chance to replace it with
ksz_rmw8() too.

Will do.

quoted

 }

 static void ksz_port_cfg(struct ksz_device *dev, int port, int offset, u8 bits,

diff --git a/drivers/net/dsa/microchip/ksz_common.c

b/drivers/net/dsa/microchip/ksz_common.c

quoted

index 7292bfe2f7ca..4cb14288ff0f 100644

--- a/drivers/net/dsa/microchip/ksz_common.c
+++ b/drivers/net/dsa/microchip/ksz_common.c

@@ -1447,6 +1447,7 @@ static const struct regmap_range ksz8873_valid_regs[] =

{

quoted

      regmap_reg_range(0x3f, 0x3f),

      /* advanced control registers */
+     regmap_reg_range(0x43, 0x43),

This register is no documented in the public documentation. Out of
curiosity, are there some where more information about this two
"reserved" register ranges: 0x3A-0x3E and 0x40-0x5F?

The current KSZ8863 and KSZ8873 datasheets available from Microchip
website do define this 0x43 register as it is a basic operation to reset
the chip.  One thing is the register bits are automatically cleared so it
does not require a second write.

Registers 0x1A-1E and 0x2A-2E are used for LinkMD feature of the PHY and
other PHY related status, so they do not apply for port 3 with 0x3A-3E.

Registers 0x40-0x5F are not used as they are not in the datasheet.