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

[Abdul Rahim, Faizal]

On 6/3/2025 8:48 am, Vladimir Oltean wrote:
> 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?
Hi Vladimir,

These are part of the statistic registers, which in IGC, reset upon read. 
When they reach their maximum value, each field remain at 0xFF.