From: Florian Fainelli <florian.fainelli@broadcom.com>
To: Nicolai Buchwitz <nb@tipi-net.de>,
Doug Berger <opendmb@gmail.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>,
Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>
Cc: 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 v4 5/8] net: bcmgenet: derive the receive buffer length from the MTU
Date: Mon, 12 Oct 2026 14:45:36 -0700 [thread overview]
Message-ID: <8f019666-30cd-4c64-a40f-43982b297d2b@broadcom.com> (raw)
In-Reply-To: <20261012-nb-genet-mtu-nn-v2-v4-5-2e2e3bfaf8cc@tipi-net.de>
On 10/12/26 02:00, Nicolai Buchwitz wrote:
> The receive buffer length is a fixed 2048 bytes. The packet ready
> thresholds keep whatever value the reset left. Neither follows the MTU.
>
> Compute the receive threshold from the MTU and program it into RBUF. The
> buffer length follows from it, with the status block on top. The MTU is
> still fixed at ETH_DATA_LEN, so the threshold comes out at the reset
> default and the buffer only grows by the status block the hardware already
> wrote. Derive UMAC_MAX_FRAME_LEN and the flow period from the MTU too, with
> a floor at ETH_DATA_LEN so a lower MTU does not stop the MAC accepting a
> standard frame.
>
> Suggested-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
> Signed-off-by: Nicolai Buchwitz <nb@tipi-net.de>
Reviewed-by: Florian Fainelli <florian.fainelli@broadcom.com>
--
Florian
next prev parent reply other threads:[~2026-10-12 21:45 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-12 9:00 [PATCH net-next v4 0/8] net: bcmgenet: support larger MTUs Nicolai Buchwitz
2026-10-12 9:00 ` [PATCH net-next v4 1/8] net: bcmgenet: ring the doorbell when the last frame of a batch is dropped Nicolai Buchwitz
2026-10-12 21:29 ` Florian Fainelli
2026-10-12 9:00 ` [PATCH net-next v4 2/8] net: bcmgenet: let the caller decide whether to start the PHY Nicolai Buchwitz
2026-10-12 9:00 ` [PATCH net-next v4 3/8] net: bcmgenet: allow a continuation descriptor without the alignment pad Nicolai Buchwitz
2026-10-13 9:19 ` netdev-bot+sashiko
2026-10-12 9:00 ` [PATCH net-next v4 4/8] net: bcmgenet: rename ENET_MAX_MTU_SIZE to ENET_MAX_FRAME_LEN Nicolai Buchwitz
2026-10-12 9:00 ` [PATCH net-next v4 5/8] net: bcmgenet: derive the receive buffer length from the MTU Nicolai Buchwitz
2026-10-12 21:45 ` Florian Fainelli [this message]
2026-10-12 9:00 ` [PATCH net-next v4 6/8] net: bcmgenet: pad transmit frames out of the packet ready window Nicolai Buchwitz
2026-10-12 21:48 ` Florian Fainelli
2026-10-13 9:19 ` netdev-bot+sashiko
2026-10-12 9:00 ` [PATCH net-next v4 7/8] net: bcmgenet: allow the MTU to be changed Nicolai Buchwitz
2026-10-12 21:38 ` Florian Fainelli
2026-10-13 9:19 ` netdev-bot+sashiko
2026-10-12 9:00 ` [PATCH net-next v4 8/8] net: bcmgenet: reassemble jumbo frames from status block fragments Nicolai Buchwitz
2026-10-12 21:49 ` Florian Fainelli
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