Subject: Re: [PATCH 4/4] net: dsa: mv88e6xxx: add PTP support for MV88E6250 family

From: Andrew Lunn <[email-masked]>
Date: Tue, 30 Jul 2019 15:58:22 +0200

> diff --git a/drivers/net/dsa/mv88e6xxx/chip.h b/drivers/net/dsa/mv88e6xxx/chip.h
> index 720cace3db4e..64872251e479 100644
> --- a/drivers/net/dsa/mv88e6xxx/chip.h
> +++ b/drivers/net/dsa/mv88e6xxx/chip.h
> @@ -273,6 +273,10 @@ struct mv88e6xxx_chip {
>  	u16 trig_config;
>  	u16 evcap_config;
>  	u16 enable_count;
> +	u32 ptp_cc_shift;
> +	u32 ptp_cc_mult;
> +	u32 ptp_cc_mult_num;
> +	u32 ptp_cc_mult_dem;

Hi Hubert

Please add these to mv88e6xxx_ptp_ops. You can create a new one of
6250 which has the different values.

>  
>  	/* Per-port timestamping resources. */
>  	struct mv88e6xxx_port_hwtstamp port_hwtstamp[DSA_MAX_PORTS];
> diff --git a/drivers/net/dsa/mv88e6xxx/ptp.c b/drivers/net/dsa/mv88e6xxx/ptp.c
> index 768d256f7c9f..51cdf4712517 100644
> --- a/drivers/net/dsa/mv88e6xxx/ptp.c
> +++ b/drivers/net/dsa/mv88e6xxx/ptp.c
> @@ -15,11 +15,38 @@
>  #include "hwtstamp.h"
>  #include "ptp.h"
>  
> -/* Raw timestamps are in units of 8-ns clock periods. */
> -#define CC_SHIFT	28
> -#define CC_MULT		(8 << CC_SHIFT)
> -#define CC_MULT_NUM	(1 << 9)
> -#define CC_MULT_DEM	15625ULL
> +/* The adjfine API clamps ppb between [-32,768,000, 32,768,000], and
> + * therefore scaled_ppm between [-2,147,483,648, 2,147,483,647].
> + * Set the maximum supported ppb to a round value smaller than the maximum.
> + *
> + * Percentually speaking, this is a +/- 0.032x adjustment of the
> + * free-running counter (0.968x to 1.032x).
> + */
> +#define MV88E6XXX_MAX_ADJ_PPB	32000000
> +
> +/* Family MV88E6250:
> + * Raw timestamps are in units of 10-ns clock periods.
> + *
> + * clkadj = scaled_ppm * 10*2^28 / (10^6 * 2^16)
> + * simplifies to
> + * clkadj = scaled_ppm * 2^7 / 5^5
> + */
> +#define MV88E6250_CC_SHIFT	28
> +#define MV88E6250_CC_MULT	(10 << MV88E6250_CC_SHIFT)
> +#define MV88E6250_CC_MULT_NUM	(1 << 7)
> +#define MV88E6250_CC_MULT_DEM	3125ULL
> +
> +/* Other families:
> + * Raw timestamps are in units of 8-ns clock periods.
> + *
> + * clkadj = scaled_ppm * 8*2^28 / (10^6 * 2^16)
> + * simplifies to
> + * clkadj = scaled_ppm * 2^9 / 5^6
> + */
> +#define MV88E6XXX_CC_SHIFT	28
> +#define MV88E6XXX_CC_MULT	(8 << MV88E6XXX_CC_SHIFT)
> +#define MV88E6XXX_CC_MULT_NUM	(1 << 9)
> +#define MV88E6XXX_CC_MULT_DEM	15625ULL

Nice comments :-)

     Andrew