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Message-Id: <20221123155116.484163-1-alexandr.lobakin@intel.com>
Date: Wed, 23 Nov 2022 16:51:16 +0100
From: Alexander Lobakin <alexandr.lobakin@...el.com>
To: Vladimir Oltean <vladimir.oltean@....com>
Cc: Alexander Lobakin <alexandr.lobakin@...el.com>,
netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>,
Eric Dumazet <edumazet@...gle.com>,
Jakub Kicinski <kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>,
Claudiu Manoil <claudiu.manoil@....com>,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH net] net: enetc: preserve TX ring priority across reconfiguration
From: Vladimir Oltean <vladimir.oltean@....com>
Date: Tue, 22 Nov 2022 15:09:36 +0200
> In the blamed commit, a rudimentary reallocation procedure for RX buffer
> descriptors was implemented, for the situation when their format changes
> between normal (no PTP) and extended (PTP).
>
> enetc_hwtstamp_set() calls enetc_close() and enetc_open() in a sequence,
> and this sequence loses information which was previously configured in
> the TX BDR Mode Register, specifically via the enetc_set_bdr_prio() call.
> The TX ring priority is configured by tc-mqprio and tc-taprio, and
> affects important things for TSN such as the TX time of packets. The
> issue manifests itself most visibly by the fact that isochron --txtime
> reports premature packet transmissions when PTP is first enabled on an
> enetc interface.
>
> Save the TX ring priority in a new field in struct enetc_bdr (occupies a
> 2 byte hole on arm64) in order to make this survive a ring reconfiguration.
>
> Fixes: 434cebabd3a2 ("enetc: Add dynamic allocation of extended Rx BD rings")
> Signed-off-by: Vladimir Oltean <vladimir.oltean@....com>
> ---
> drivers/net/ethernet/freescale/enetc/enetc.c | 8 ++++---
> drivers/net/ethernet/freescale/enetc/enetc.h | 1 +
> .../net/ethernet/freescale/enetc/enetc_qos.c | 21 ++++++++++++-------
> 3 files changed, 19 insertions(+), 11 deletions(-)
[...]
> err = enetc_setup_taprio(ndev, taprio);
> -
> - if (err)
> - for (i = 0; i < priv->num_tx_rings; i++)
> - enetc_set_bdr_prio(hw, priv->tx_ring[i]->index,
> - taprio->enable ? 0 : i);
> + if (err) {
> + for (i = 0; i < priv->num_tx_rings; i++) {
> + tx_ring = priv->tx_ring[i];
> + tx_ring->prio = taprio->enable ? 0 : i;
Side note: is that `taprio ? 0 : i` correct? It's an error path
IIUC, why not just unconditional 0?
I guess it is, so
Reviewed-by: Alexander Lobakin <alexandr.lobakin@...el.com>
> + enetc_set_bdr_prio(hw, tx_ring->index, tx_ring->prio);
> + }
> + }
>
> return err;
> }
> --
> 2.34.1
Thanks,
Olek
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