From: Jakub Kicinski <kuba@kernel.org>
To: Nicolai Buchwitz <nb@tipi-net.de>
Cc: Doug Berger <opendmb@gmail.com>,
Florian Fainelli <florian.fainelli@broadcom.com>,
Broadcom internal kernel review list
<bcm-kernel-feedback-list@broadcom.com>,
Andrew Lunn <andrew+netdev@lunn.ch>,
"David S. Miller" <davem@davemloft.net>,
Eric Dumazet <edumazet@kernel.org>,
Paolo Abeni <pabeni@redhat.com>,
netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
Dave Stevenson <dave.stevenson@raspberrypi.com>,
Justin Chen <justin.chen@broadcom.com>,
Pierre-Marin Leclercq <pierremarinleclercq88@gmail.com>,
Florian Fainelli <f.fainelli@gmail.com>
Subject: Re: [PATCH net-next v5 6/8] net: bcmgenet: pad transmit frames out of the packet ready window
Date: Fri, 16 Oct 2026 18:25:08 -0700 [thread overview]
Message-ID: <20261016182508.1100f391@kernel.org> (raw)
In-Reply-To: <20261013-nb-genet-mtu-nn-v2-v5-6-076b6fc240be@tipi-net.de>
On Tue, 13 Oct 2026 16:20:35 +0200 Nicolai Buchwitz wrote:
> A frame that ends a few bytes past the transmit packet ready threshold
> stops the transmitter as soon as a shorter frame follows. Tx DMA then
> refuses to halt, so every later bcmgenet_init_dma() fails and the interface
> cannot be opened again. IP fragmentation generates that pattern on every
> datagram, full frames and a short tail.
This is really odd. Sounds like the IP can't really support high MTU
properly. Should the user be somehow informed that the driver will
append out-of-spec bytes to their frames or better still opt into
this hack?
next prev parent reply other threads:[~2026-10-17 1:25 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-13 14:20 [PATCH net-next v5 0/8] net: bcmgenet: support larger MTUs Nicolai Buchwitz
2026-10-13 14:20 ` [PATCH net-next v5 1/8] net: bcmgenet: ring the doorbell when the last frame of a batch is dropped Nicolai Buchwitz
2026-10-13 14:20 ` [PATCH net-next v5 2/8] net: bcmgenet: let the caller decide whether to start the PHY Nicolai Buchwitz
2026-10-13 14:20 ` [PATCH net-next v5 3/8] net: bcmgenet: allow a continuation descriptor without the alignment pad Nicolai Buchwitz
2026-10-13 14:20 ` [PATCH net-next v5 4/8] net: bcmgenet: rename ENET_MAX_MTU_SIZE to ENET_MAX_FRAME_LEN Nicolai Buchwitz
2026-10-13 14:20 ` [PATCH net-next v5 5/8] net: bcmgenet: derive the receive buffer length from the MTU Nicolai Buchwitz
2026-10-13 14:20 ` [PATCH net-next v5 6/8] net: bcmgenet: pad transmit frames out of the packet ready window Nicolai Buchwitz
2026-10-14 14:22 ` netdev-bot+sashiko
2026-10-15 8:48 ` Nicolai Buchwitz
2026-10-17 1:25 ` Jakub Kicinski [this message]
2026-10-17 6:29 ` Nicolai Buchwitz
2026-10-13 14:20 ` [PATCH net-next v5 7/8] net: bcmgenet: allow the MTU to be changed Nicolai Buchwitz
2026-10-14 14:22 ` netdev-bot+sashiko
2026-10-15 8:55 ` Nicolai Buchwitz
2026-10-17 1:24 ` Jakub Kicinski
2026-10-17 6:26 ` Nicolai Buchwitz
2026-10-13 14:20 ` [PATCH net-next v5 8/8] net: bcmgenet: reassemble jumbo frames from status block fragments Nicolai Buchwitz
2026-10-14 14:22 ` netdev-bot+sashiko
2026-10-15 8:56 ` Nicolai Buchwitz
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