Re: [PATCH iwl-next v8 11/11] igc: add support to get frame preemption statistics via ethtool

Vladimir Oltean
2025-03-06T00:50:07Z

On Wed, Mar 05, 2025 at 08:00:26AM -0500, Faizal Rahim wrote:
> +/* Received out of order packets with SMD-C */
> +#define IGC_PRMEXCPRCNT_OOO_SMDC 0x000000FF
> +/* Received out of order packets with SMD-C and wrong Frame CNT */
> +#define IGC_PRMEXCPRCNT_OOO_FRAME_CNT 0x0000FF00
> +/* Received out of order packets with SMD-C and wrong Frag CNT */
> +#define IGC_PRMEXCPRCNT_OOO_FRAG_CNT 0x00FF0000
> +/* Received packets with SMD-S and wrong Frag CNT and Frame CNT */
> +#define IGC_PRMEXCPRCNT_MISS_FRAME_FRAG_CNT 0xFF000000
>
> +/**
> + * igc_ethtool_get_frame_ass_error - Get the frame assembly error count.
> + * @reg_value: Register value for IGC_PRMEXCPRCNT
> + * Return: The count of frame assembly errors.
> + */
> +static u64 igc_ethtool_get_frame_ass_error(u32 reg_value)
> +{
> + u32 ooo_frame_cnt, ooo_frag_cnt; /* Out of order statistics */
> + u32 miss_frame_frag_cnt;
> +
> + ooo_frame_cnt = FIELD_GET(IGC_PRMEXCPRCNT_OOO_FRAME_CNT, reg_value);
> + ooo_frag_cnt = FIELD_GET(IGC_PRMEXCPRCNT_OOO_FRAG_CNT, reg_value);
> + miss_frame_frag_cnt = FIELD_GET(IGC_PRMEXCPRCNT_MISS_FRAME_FRAG_CNT, reg_value);
> +
> + return ooo_frame_cnt + ooo_frag_cnt + miss_frame_frag_cnt;
> +}

These counters are quite small (8 bits each). What is their behavior
once they reach 255? Saturate? Truncate? Do they clear on read?