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SubjectRe: [PATCH v2] net: stmmac: correct MAC propagation delay
From
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
>
>

--
Pengutronix e.K. | Johannes Zink |
Steuerwalder Str. 21 | https://www.pengutronix.de/ |
31137 Hildesheim, Germany | Phone: +49-5121-206917-0 |
Amtsgericht Hildesheim, HRA 2686| Fax: +49-5121-206917-5555 |

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