From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pj1-f97.google.com (mail-pj1-f97.google.com [209.85.216.97]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 4A4A03B1014 for ; Mon, 12 Oct 2026 21:38:14 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.216.97 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791841095; cv=none; b=IFPbnJWUiVy1Oj7BXO8+PZcTE4zuGRsjbisFUJn4Vc0xcTc4+Ybzr+tv6HdMC34zPrtoyH6p2a0qboha1tuD8A6Wo9kE8JNDjXNt6S6yUsotC6L7s/KjrR/vEyorNpY2GF63/2HmF+jxSquWAS4n51vBv1/z9c+/k0hOeOJsodI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791841095; c=relaxed/simple; bh=qQaH3L8BpbCXELnWiv04IgP9typ9bfpn74Gyn/ZyzO8=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=VMA1GHxTgtzlIlda5ZR0G6FBop98GjOUADHYFCOIYk2VjZTJPDr0qIy/457LgZqmp6kZUJFhyJaslSRmRGPc+nbXth/lxQbbrWEACeCiagbgLlhhqO3+jmZmjHLYtgrFSdgk4aw+g5zc/e6QbR/WJSft6nZVTfLuLEhhG4NUOAM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=broadcom.com; spf=fail smtp.mailfrom=broadcom.com; dkim=pass (1024-bit key) header.d=broadcom.com header.i=@broadcom.com header.b=VeJmzXAk; arc=none smtp.client-ip=209.85.216.97 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=broadcom.com Authentication-Results: smtp.subspace.kernel.org; spf=fail smtp.mailfrom=broadcom.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=broadcom.com header.i=@broadcom.com header.b="VeJmzXAk" Received: by mail-pj1-f97.google.com with SMTP id 98e67ed59e1d1-39647aa9d52so1343220a91.0 for ; Mon, 12 Oct 2026 14:38:14 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1791841094; x=1792445894; h=content-transfer-encoding:content-type:in-reply-to:autocrypt:from :content-language:references:cc:to:subject:user-agent:mime-version :date:message-id:dkim-signature:x-gm-gg:x-gm-message-state:from:to :cc:subject:date:message-id:reply-to:content-type; bh=3vlSbo4Pdnjbh8waT5OPK3ABW3rN2NX05GJe3pGPoqU=; b=IOFAyzh5gBrOZNw7WWvizY4Wb60u/BOwpUod0S2tfjd4S3G59FRSZzqnGIUWMeZNz6 JzjHXeBtAKNRxpMLE9ZpPE44exTeYbwJ2/0M196SpkcGROLErGPd7O3vjez1HIeEkjWx S6AEvGgMgBotXk2ZX2d+QDAKAmbDyzy84OeFPLjRjXBn+H5H08VB8eBKHIiSQydJZmxo nWfNNgNb/khov1wS6ZfGC+eP23XiFrHaE73hOR6D4l/tTJU6+qI242qy6h9MFpdA6DF+ FVKNofS/KurDiNx755W0N40PrWkZ+hVAb/i2Fvq7mA0OYouPdmfnR0/BdlMmmise6ryQ Ofvg== X-Forwarded-Encrypted: i=1; AKwUvBy3ft6MX8fD3RTpNM5V8H0RHqCSqCeIyEzD7n1uvPx5NM1eACtpy4+BM3nDlHa9qv9oXURWOpUTPUqDqNU=@vger.kernel.org X-Gm-Message-State: AFq9FYKbkoxhi2e1JGltIEnSj2RYdxjFF922GaWXAMJYHliUJ+m10RUg G5qzw/UzQBHIbuqs7+rkZqC2yjWgl2BXggwAmuzHpC+aLb3T/OFopF7Oy3m45N09EeBKewiby5x U0ItXYjf+qH1xfLnLe5O9OiwbYS0BCW9ag3HT3ufA8Qau9bPDVXW8yE9IcchdNNHMH6NDkOe00T tSeDW81BZhNnN7CFOFFFk5JG2dgvNz+YP0ZAOQUsXqNf4T7X3/F2O5kEyhDMCLpx0MOZ7/OPnhv +xx6YSOlDluVoiQpK1/f6u9 X-Gm-Gg: AYBFou0Lbvaf4UFuD1esQfJOak+mFJuh0Shyb0irn4Utqr34Bdpi2P0ab/SOk1u7Uit M32/jxVRz4BljOFIEc83oWBomY/L7m3sTllnz9jO/2v357WDdw3vNN5ZH8Bgdcxd9gn6EpgA0z7 1JqL9ZwMwLIynTRGYb/z+V67rQWpxiwyYCaKWZX7oG0IL3ujVWVIvpGTY8nULQ1GWHVJ/FJBrxK EmzeIdum+RDiNFn3z61PzI+GWzIrPLe2uCvQby11A/Go8XsqbEp1kkKZLgHjpwPvwJrPZ0eDpsf KP6U1e4+vsOVxAJWybNMv5KuXRsk2dXkCsI2aKqD8s9K/qV/FtwOD1Cjltunx7l252xcCmaRRte aaoRQA1nEkAYfQ+MydsUz+/bka/m6pELGUMK/9D3AbQsSGJLXypHy+Ezz589F6CowTvTGN4Mkzg m4HGaVOaTpXO72Gjp9c675tjGTc0v5tQDrodpNxRjrJ+U= X-Received: by 2002:a17:90b:2d06:b0:3a7:cffb:8b8c with SMTP id 98e67ed59e1d1-3ab3ad0e976mr5455828a91.43.1791841093312; Mon, 12 Oct 2026 14:38:13 -0700 (PDT) Received: from smtp-us-east1-p01-i01-si01.dlp.protect.broadcom.com (address-144-49-247-120.dlp.protect.broadcom.com. [144.49.247.120]) by smtp-relay.gmail.com with ESMTPS id 98e67ed59e1d1-3abdd5d09d2sm2560871a91.8.2026.10.12.14.38.12 for (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Mon, 12 Oct 2026 14:38:13 -0700 (PDT) X-Relaying-Domain: broadcom.com X-CFilter-Loop: Reflected Received: by mail-dy1-f200.google.com with SMTP id 5a478bee46e88-35b68bc1985so981601eec.1 for ; Mon, 12 Oct 2026 14:38:12 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=broadcom.com; s=google; t=1791841091; x=1792445891; darn=vger.kernel.org; h=content-transfer-encoding:content-type:in-reply-to:autocrypt:from :content-language:references:cc:to:subject:user-agent:mime-version :date:message-id:from:to:cc:subject:date:message-id:reply-to :content-type; bh=3vlSbo4Pdnjbh8waT5OPK3ABW3rN2NX05GJe3pGPoqU=; b=VeJmzXAkN/EWp8o3UehtbNvLRrnHv/mHMkHpWBiWtRVKUs9YBsZRG60qmxcUglBrlq RFTAITuJpiZBXvocOjV4CKivJnOfZ74PCjKZaH0aDMuEaVjWtrgU07Hd4ZGkKNGZWWov dIyZ+tEvHk47BqhYs+YF8iuQ+aEtmon6qRRrU= X-Forwarded-Encrypted: i=1; AKwUvBxqgEosTyH9kdFZD05kmC0R7d/kXCvbLiBpCI1sxKljUycZcwfrYx5emL0TxZ5WNiMcRmf5n8g6nKTGnHs=@vger.kernel.org X-Received: by 2002:a05:7022:e804:b0:13c:f65c:d5b5 with SMTP id a92af1059eb24-16a0b37d130mr15430924c88.3.1791841091450; Mon, 12 Oct 2026 14:38:11 -0700 (PDT) X-Received: by 2002:a05:7022:e804:b0:13c:f65c:d5b5 with SMTP id a92af1059eb24-16a0b37d130mr15430890c88.3.1791841090564; Mon, 12 Oct 2026 14:38:10 -0700 (PDT) Received: from [10.67.48.245] ([192.19.223.252]) by smtp.gmail.com with ESMTPSA id a92af1059eb24-1699718c547sm31698113c88.3.2026.10.12.14.38.08 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 12 Oct 2026 14:38:09 -0700 (PDT) Message-ID: <6ad6d66a-57a2-4f9e-8245-0ab060f07606@broadcom.com> Date: Mon, 12 Oct 2026 14:38:07 -0700 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH net-next v4 7/8] net: bcmgenet: allow the MTU to be changed To: Nicolai Buchwitz , Doug Berger , Broadcom internal kernel review list , Andrew Lunn , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Dave Stevenson , Justin Chen , Pierre-Marin Leclercq , Florian Fainelli References: <20261012-nb-genet-mtu-nn-v2-v4-0-2e2e3bfaf8cc@tipi-net.de> <20261012-nb-genet-mtu-nn-v2-v4-7-2e2e3bfaf8cc@tipi-net.de> Content-Language: en-US, fr-FR From: Florian Fainelli Autocrypt: addr=florian.fainelli@broadcom.com; keydata= xsBNBFPAG8ABCAC3EO02urEwipgbUNJ1r6oI2Vr/+uE389lSEShN2PmL3MVnzhViSAtrYxeT M0Txqn1tOWoIc4QUl6Ggqf5KP6FoRkCrgMMTnUAINsINYXK+3OLe7HjP10h2jDRX4Ajs4Ghs JrZOBru6rH0YrgAhr6O5gG7NE1jhly+EsOa2MpwOiXO4DE/YKZGuVe6Bh87WqmILs9KvnNrQ PcycQnYKTVpqE95d4M824M5cuRB6D1GrYovCsjA9uxo22kPdOoQRAu5gBBn3AdtALFyQj9DQ KQuc39/i/Kt6XLZ/RsBc6qLs+p+JnEuPJngTSfWvzGjpx0nkwCMi4yBb+xk7Hki4kEslABEB AAHNMEZsb3JpYW4gRmFpbmVsbGkgPGZsb3JpYW4uZmFpbmVsbGlAYnJvYWRjb20uY29tPsLB IQQQAQgAywUCZWl41AUJI+Jo+hcKAAG/SMv+fS3xUQWa0NryPuoRGjsA3SAUAAAAAAAWAAFr ZXktdXNhZ2UtbWFza0BwZ3AuY29tjDAUgAAAAAAgAAdwcmVmZXJyZWQtZW1haWwtZW5jb2Rp bmdAcGdwLmNvbXBncG1pbWUICwkIBwMCAQoFF4AAAAAZGGxkYXA6Ly9rZXlzLmJyb2FkY29t Lm5ldAUbAwAAAAMWAgEFHgEAAAAEFQgJChYhBNXZKpfnkVze1+R8aIExtcQpvGagAAoJEIEx tcQpvGagWPEH/2l0DNr9QkTwJUxOoP9wgHfmVhqc0ZlDsBFv91I3BbhGKI5UATbipKNqG13Z TsBrJHcrnCqnTRS+8n9/myOF0ng2A4YT0EJnayzHugXm+hrkO5O9UEPJ8a+0553VqyoFhHqA zjxj8fUu1px5cbb4R9G4UAySqyeLLeqnYLCKb4+GklGSBGsLMYvLmIDNYlkhMdnnzsSUAS61 WJYW6jjnzMwuKJ0ZHv7xZvSHyhIsFRiYiEs44kiYjbUUMcXor/uLEuTIazGrE3MahuGdjpT2 IOjoMiTsbMc0yfhHp6G/2E769oDXMVxCCbMVpA+LUtVIQEA+8Zr6mX0Yk4nDS7OiBlvOwE0E U8AbwQEIAKxr71oqe+0+MYCc7WafWEcpQHFUwvYLcdBoOnmJPxDwDRpvU5LhqSPvk/yJdh9k 4xUDQu3rm1qIW2I9Puk5n/Jz/lZsqGw8T13DKyu8eMcvaA/irm9lX9El27DPHy/0qsxmxVmU pu9y9S+BmaMb2CM9IuyxMWEl9ruWFS2jAWh/R8CrdnL6+zLk60R7XGzmSJqF09vYNlJ6Bdbs MWDXkYWWP5Ub1ZJGNJQ4qT7g8IN0qXxzLQsmz6tbgLMEHYBGx80bBF8AkdThd6SLhreCN7Uh IR/5NXGqotAZao2xlDpJLuOMQtoH9WVNuuxQQZHVd8if+yp6yRJ5DAmIUt5CCPcAEQEAAcLB gQQYAQIBKwUCU8AbwgUbDAAAAMBdIAQZAQgABgUCU8AbwQAKCRCTYAaomC8PVQ0VCACWk3n+ obFABEp5Rg6Qvspi9kWXcwCcfZV41OIYWhXMoc57ssjCand5noZi8bKg0bxw4qsg+9cNgZ3P N/DFWcNKcAT3Z2/4fTnJqdJS//YcEhlr8uGs+ZWFcqAPbteFCM4dGDRruo69IrHfyyQGx16s CcFlrN8vD066RKevFepb/ml7eYEdN5SRALyEdQMKeCSf3mectdoECEqdF/MWpfWIYQ1hEfdm C2Kztm+h3Nkt9ZQLqc3wsPJZmbD9T0c9Rphfypgw/SfTf2/CHoYVkKqwUIzI59itl5Lze+R5 wDByhWHx2Ud2R7SudmT9XK1e0x7W7a5z11Q6vrzuED5nQvkhAAoJEIExtcQpvGagugcIAJd5 EYe6KM6Y6RvI6TvHp+QgbU5dxvjqSiSvam0Ms3QrLidCtantcGT2Wz/2PlbZqkoJxMQc40rb fXa4xQSvJYj0GWpadrDJUvUu3LEsunDCxdWrmbmwGRKqZraV2oG7YEddmDqOe0Xm/NxeSobc MIlnaE6V0U8f5zNHB7Y46yJjjYT/Ds1TJo3pvwevDWPvv6rdBeV07D9s43frUS6xYd1uFxHC 7dZYWJjZmyUf5evr1W1gCgwLXG0PEi9n3qmz1lelQ8lSocmvxBKtMbX/OKhAfuP/iIwnTsww 95A2SaPiQZA51NywV8OFgsN0ITl2PlZ4Tp9hHERDe6nQCsNI/Us= In-Reply-To: <20261012-nb-genet-mtu-nn-v2-v4-7-2e2e3bfaf8cc@tipi-net.de> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-DetectorID-Processed: b00c1d49-9d2e-4205-b15f-d015386d3d5e On 10/12/26 02:00, Nicolai Buchwitz wrote: > The driver never sets dev->max_mtu, so the MTU is stuck at ETH_DATA_LEN. > > One descriptor reaches as far as the packet ready threshold, so derive the > maximum from it. The threshold registers are 8 bit in units of 16 bytes and > want a multiple of the 256 byte burst size. A descriptor is one page and > also holds skb_shared_info behind the frame. On 4K pages the page is the > tighter limit and leaves 3564 bytes. That includes room for a VLAN tag so a > VLAN interface can run at the parent MTU. The MAC accepts a little more > than one descriptor holds, so a double tagged frame at that maximum is > dropped as fragmented until a later patch reassembles those. > > Resize the buffers and rewrite the registers in place. The PHY keeps > running and the link stays up. Two MTUs at or below ETH_DATA_LEN derive the > same values, so a change between them skips the restart. > > A failed allocation retries at the previous size. If that fails too, take > the interface down. Running on rings that were never allocated is worse. > > Suggested-by: Dave Stevenson > Link: https://github.com/raspberrypi/linux/issues/5561 > Tested-by: Pierre-Marin Leclercq > Signed-off-by: Nicolai Buchwitz Reviewed-by: Florian Fainelli -- Florian