netdev - Re: [PATCH] net: sparx5: Fix invalid timestamps

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Message-ID: <20240914190343.rq3fhgadxeuvc5qb@DEN-DL-M70577>
Date: Sat, 14 Sep 2024 19:03:43 +0000
From: Daniel Machon <daniel.machon@...rochip.com>
To: Aakash Menon <aakash.r.menon@...il.com>
CC: <davem@...emloft.net>, <edumazet@...gle.com>, <kuba@...nel.org>,
	<pabeni@...hat.com>, <lars.povlsen@...rochip.com>,
	<Steen.Hegelund@...rochip.com>, <UNGLinuxDriver@...rochip.com>,
	<aakash.menon@...tempis.com>, <horms@...nel.org>,
	<horatiu.vultur@...rochip.com>, <netdev@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] net: sparx5: Fix invalid timestamps

> Bit 270-271 are occasionally unexpectedly set by the hardware.
> 
> This issue was observed with 10G SFPs causing huge time errors (> 30ms) in PTP.
> 
> Only 30 bits are needed for the nanosecond part of the timestamp, clear 2 most significant bits before extracting timestamp from the internal frame header.
> 
> Signed-off-by: Aakash Menon <aakash.menon@...tempis.com>
> ---
>  drivers/net/ethernet/microchip/sparx5/sparx5_packet.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/microchip/sparx5/sparx5_packet.c b/drivers/net/ethernet/microchip/sparx5/sparx5_packet.c
> index f3f5fb420468..a05263488851 100644
> --- a/drivers/net/ethernet/microchip/sparx5/sparx5_packet.c
> +++ b/drivers/net/ethernet/microchip/sparx5/sparx5_packet.c
> @@ -45,8 +45,12 @@ void sparx5_ifh_parse(u32 *ifh, struct frame_info *info)
>         fwd = (fwd >> 5);
>         info->src_port = FIELD_GET(GENMASK(7, 1), fwd);
> 
> +       /*
> +        * Bit 270-271 are occasionally unexpectedly set by the hardware,
> +        * clear bits before extracting timestamp
> +        */
>         info->timestamp =
> -               ((u64)xtr_hdr[2] << 24) |
> +               ((u64)(xtr_hdr[2] & 0x3F) << 24) |
>                 ((u64)xtr_hdr[3] << 16) |
>                 ((u64)xtr_hdr[4] <<  8) |
>                 ((u64)xtr_hdr[5] <<  0);
> --
> 2.46.0
>

Hi Aakash,

I will (or somebody else) try to reproduce and test this at the
beginning of the next week.

Meanwhile, you can address the issues that Simon mentioned.

Thanks.

/Daniel