Re: [PATCH v2] net: stmmac: correct MAC propagation delay

[Johannes Zink]

Hi Richard,

On 7/26/23 22:57, Richard Cochran wrote:
> On Mon, Jul 24, 2023 at 12:01:31PM +0200, Johannes Zink wrote:
>
> Earlier versions of the IP core return zero from these...
>
> > +#define	PTP_TS_INGR_LAT	0x68	/* MAC internal Ingress Latency */
> > +#define	PTP_TS_EGR_LAT	0x6c	/* MAC internal Egress Latency */

good catch. Gonna send a v3 with a check to and set the values for dwmac v5 only.

Best regards
Johannes


> and so...
>
> > +static void correct_latency(struct stmmac_priv *priv)
> > +{
> > +	void __iomem *ioaddr = priv->ptpaddr;
> > +	u32 reg_tsic, reg_tsicsns;
> > +	u32 reg_tsec, reg_tsecsns;
> > +	u64 scaled_ns;
> > +	u32 val;
> > +
> > +	/* MAC-internal ingress latency */
> > +	scaled_ns = readl(ioaddr + PTP_TS_INGR_LAT);
> > +
> > +	/* See section 11.7.2.5.3.1 "Ingress Correction" on page 4001 of
> > +	 * i.MX8MP Applications Processor Reference Manual Rev. 1, 06/2021
> > +	 */
> > +	val = readl(ioaddr + PTP_TCR);
> > +	if (val & PTP_TCR_TSCTRLSSR)
> > +		/* nanoseconds field is in decimal format with granularity of 1ns/bit */
> > +		scaled_ns = ((u64)NSEC_PER_SEC << 16) - scaled_ns;
> > +	else
> > +		/* nanoseconds field is in binary format with granularity of ~0.466ns/bit */
> > +		scaled_ns = ((1ULL << 31) << 16) -
> > +			DIV_U64_ROUND_CLOSEST(scaled_ns * PSEC_PER_NSEC, 466U);
> > +
> > +	reg_tsic = scaled_ns >> 16;
> > +	reg_tsicsns = scaled_ns & 0xff00;
> > +
> > +	/* set bit 31 for 2's compliment */
> > +	reg_tsic |= BIT(31);
> > +
> > +	writel(reg_tsic, ioaddr + PTP_TS_INGR_CORR_NS);
>
> here reg_tsic = 0x80000000 for a correction of -2.15 seconds! >
> @Jakub  Can you please revert this patch?
>
> Thanks,
> Richard

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