Re: [PATCH net-next v4] net: dsa: mv88e6xxx: Add erratum 3.14 for 88E6390X and 88E6190X

[Vladimir Oltean <olteanv@gmail.com>]

On Thu, Jul 27, 2023 at 10:25:50AM +0200, Ante Knezic wrote:
> Fixes XAUI/RXAUI lane alignment errors.
> Issue causes dropped packets when trying to communicate over
> fiber via SERDES lanes of port 9 and 10.
> Errata document applies only to 88E6190X and 88E6390X devices.
> Requires poking in undocumented registers.
> 
> Signed-off-by: Ante Knezic <ante.knezic@helmholz.de>
> ---
> V4 : Rework as suggested by Vladimir Oltean <olteanv@gmail.com>
>      and Russell King <linux@armlinux.org.uk>
>  * print error in case of failure to apply erratum
>  * use mdiobus_c45_write instead of mdiodev_c45_write
>  * use bool variable instead of embedding a chip pointer inside
>    pcs struct.
> V3 : Rework to fit the new phylink_pcs infrastructure
> V2 : Rework as suggested by Andrew Lunn <andrew@lun.ch> 
>  * make int lanes[] const 
>  * reorder prod_nums
>  * update commit message to indicate we are dealing with
>    undocumented Marvell registers and magic values
> ---
>  drivers/net/dsa/mv88e6xxx/pcs-639x.c | 45 ++++++++++++++++++++++++++++++++++++
>  1 file changed, 45 insertions(+)
> 
> diff --git a/drivers/net/dsa/mv88e6xxx/pcs-639x.c b/drivers/net/dsa/mv88e6xxx/pcs-639x.c
> index 98dd49dac421..ba373656bfe1 100644
> --- a/drivers/net/dsa/mv88e6xxx/pcs-639x.c
> +++ b/drivers/net/dsa/mv88e6xxx/pcs-639x.c
> @@ -20,6 +20,7 @@ struct mv88e639x_pcs {
>  	struct mdio_device mdio;
>  	struct phylink_pcs sgmii_pcs;
>  	struct phylink_pcs xg_pcs;
> +	bool erratum_3_14;
>  	bool supports_5g;
>  	phy_interface_t interface;
>  	unsigned int irq;
> @@ -205,13 +206,53 @@ static void mv88e639x_sgmii_pcs_pre_config(struct phylink_pcs *pcs,
>  	mv88e639x_sgmii_pcs_control_pwr(mpcs, false);
>  }
>  
> +static int mv88e6390_erratum_3_14(struct mv88e639x_pcs *mpcs)
> +{
> +	const int lanes[] = { MV88E6390_PORT9_LANE0, MV88E6390_PORT9_LANE1,
> +		MV88E6390_PORT9_LANE2, MV88E6390_PORT9_LANE3,
> +		MV88E6390_PORT10_LANE0, MV88E6390_PORT10_LANE1,
> +		MV88E6390_PORT10_LANE2, MV88E6390_PORT10_LANE3 };
> +	int err, i;
> +
> +	/* 88e6190x and 88e6390x errata 3.14:
> +	 * After chip reset, SERDES reconfiguration or SERDES core
> +	 * Software Reset, the SERDES lanes may not be properly aligned
> +	 * resulting in CRC errors
> +	 */
> +
> +	for (i = 0; i < ARRAY_SIZE(lanes); i++) {
> +		err = mdiobus_c45_write(mpcs->mdio.bus, lanes[i],
> +					MDIO_MMD_PHYXS,
> +					0xf054, 0x400C);
> +		if (err)
> +			return err;
> +
> +		err = mdiobus_c45_write(mpcs->mdio.bus, lanes[i],
> +					MDIO_MMD_PHYXS,
> +					0xf054, 0x4000);
> +		if (err)
> +			return err;
> +	}
> +
> +	return 0;
> +}
> +
>  static int mv88e639x_sgmii_pcs_post_config(struct phylink_pcs *pcs,
>  					   phy_interface_t interface)
>  {
>  	struct mv88e639x_pcs *mpcs = sgmii_pcs_to_mv88e639x_pcs(pcs);
> +	int err;
>  
>  	mv88e639x_sgmii_pcs_control_pwr(mpcs, true);
>  
> +	if (mpcs->erratum_3_14) {
> +		err = mv88e6390_erratum_3_14(mpcs);
> +		if (err)
> +			dev_err(mpcs->mdio.dev.parent,
> +				"failed to apply erratum 3.14: %pe\n",
> +				ERR_PTR(err));
> +	}
> +
>  	return 0;
>  }
>  
> @@ -524,6 +565,10 @@ static int mv88e6390_pcs_init(struct mv88e6xxx_chip *chip, int port)
>  	mpcs->xg_pcs.ops = &mv88e6390_xg_pcs_ops;
>  	mpcs->xg_pcs.neg_mode = true;
>  
> +	if (chip->info->prod_num == MV88E6XXX_PORT_SWITCH_ID_PROD_6190X ||
> +	    chip->info->prod_num == MV88E6XXX_PORT_SWITCH_ID_PROD_6390X)
> +		mpcs->erratum_3_14 = true;
> +
>  	err = mv88e639x_pcs_setup_irq(mpcs, chip, port);
>  	if (err)
>  		goto err_free;
> -- 
> 2.11.0
> 

It's good practice that, if you had a conversation with Russell on previous
versions of the patch, to keep him CCed on newer versions of it.