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

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Message-ID:
 <DM3PR11MB873655B75D0FF0E386567293EC2CA@DM3PR11MB8736.namprd11.prod.outlook.com>
Date: Thu, 7 Aug 2025 00:53:26 +0000
From: <Tristram.Ha@...rochip.com>
To: <o.rempel@...gutronix.de>
CC: <linux@...pel-privat.de>, <Woojung.Huh@...rochip.com>, <andrew@...n.ch>,
	<olteanv@...il.com>, <maxime.chevallier@...tlin.com>, <davem@...emloft.net>,
	<edumazet@...gle.com>, <kuba@...nel.org>, <pabeni@...hat.com>,
	<UNGLinuxDriver@...rochip.com>, <netdev@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>
Subject: RE: [PATCH net] net: dsa: microchip: Fix KSZ8863 reset problem

> On Fri, Aug 01, 2025 at 05:22:53PM -0700, Tristram.Ha@...rochip.com wrote:
> > From: Tristram Ha <tristram.ha@...rochip.com>
> >
> > 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!
> 
> > Fixes: d0dec3333040 ("net: dsa: microchip: Add register access control for KSZ8873
> chip")
> > Signed-off-by: Tristram Ha <tristram.ha@...rochip.com>
> > ---
> >  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.

> >  }
> >
> >  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
> > 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[] =
> {
> >       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.