Re: [PATCH net-next v3 7/7] net: dsa: microchip: Disable PTP function of KSZ8463

[Vladimir Oltean <olteanv@gmail.com>]

On Tue, Jul 08, 2025 at 05:32:33PM -0700, Tristram.Ha@microchip.com wrote:
> From: Tristram Ha <tristram.ha@microchip.com>
> 
> The PTP function of KSZ8463 is on by default.  However, its proprietary
> way of storing timestamp directly in a reserved field inside the PTP
> message header is not suitable for use with the current Linux PTP stack
> implementation.  It is necessary to disable the PTP function to not
> interfere the normal operation of the MAC.
> 
> Signed-off-by: Tristram Ha <tristram.ha@microchip.com>
> ---
>  drivers/net/dsa/microchip/ksz8.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> diff --git a/drivers/net/dsa/microchip/ksz8.c b/drivers/net/dsa/microchip/ksz8.c
> index ddbd05c44ce5..fd4a000487d6 100644
> --- a/drivers/net/dsa/microchip/ksz8.c
> +++ b/drivers/net/dsa/microchip/ksz8.c
> @@ -1761,6 +1761,17 @@ void ksz8_config_cpu_port(struct dsa_switch *ds)
>  					   reg16(dev, KSZ8463_REG_DSP_CTRL_6),
>  					   COPPER_RECEIVE_ADJUSTMENT, 0);
>  		}
> +
> +		/* Turn off PTP function as the switch's proprietary way of
> +		 * handling timestamp is not supported in current Linux PTP
> +		 * stack implementation.
> +		 */
> +		regmap_update_bits(ksz_regmap_16(dev),
> +				   reg16(dev, KSZ8463_PTP_MSG_CONF1),
> +				   PTP_ENABLE, 0);
> +		regmap_update_bits(ksz_regmap_16(dev),
> +				   reg16(dev, KSZ8463_PTP_CLK_CTRL),
> +				   PTP_CLK_ENABLE, 0);
>  	}
>  }
>  
> -- 
> 2.34.1
> 

What prevents the user from later enabling this through
ksz_set_hwtstamp_config(HWTSTAMP_TX_ONESTEP_P2P)?