From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from esa.microchip.iphmx.com (esa.microchip.iphmx.com [68.232.154.123]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 13CD0350D46; Tue, 3 Mar 2026 18:04:46 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=68.232.154.123 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772561087; cv=none; b=DaRRVLRjcBAYqpkUq5CRXW0RJQC6N7bxkKU3s3UuHkgSc/PqEXtIkHrqobwBIBqufFJYSYYBwpFUd3AobJQnXrglS3SOhBCeR7HeDsaopqe4q2zhHJXxUSRSOpYmnlrikqhJloLbTFJoowq1JPyH76ov9e6Y2Wxojryl/qe5G0U= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772561087; c=relaxed/simple; bh=GTKkgOixrxzmHD3zUijlM5vksm6oyDRMA71BnCEXes0=; h=From:To:CC:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=rTInptnDKtNnOh6XvDMZ/xkoq7XeMSJQJ5sLUqektq7J6VgX9X8rqPi/9ldQIwvDbSMG8Yk2BibRsYcaqYD6qST0gXwVlTEMOBSpTKH2oi/Zd3vOalFRBFKAQxDGVZRvk15QZUu6vd+fHKpIePOLJPc825tTvJzEAYmNQouFznw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=microchip.com; spf=pass smtp.mailfrom=microchip.com; dkim=pass (2048-bit key) header.d=microchip.com header.i=@microchip.com header.b=pmvoDyjZ; arc=none smtp.client-ip=68.232.154.123 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=microchip.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=microchip.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=microchip.com header.i=@microchip.com header.b="pmvoDyjZ" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=microchip.com; i=@microchip.com; q=dns/txt; s=mchp; t=1772561086; x=1804097086; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=GTKkgOixrxzmHD3zUijlM5vksm6oyDRMA71BnCEXes0=; b=pmvoDyjZHd29uYp1y3LLMREylu+SgKgEhzOGgheDqVHDv9qf4Pv+fPDQ VCsxXrx1ai0BW3ImlwMQ8bEEqp9hKmLN+RG14gU5HJwAn19VS4C87er8D NP8WDM1sYhH3BVkeO+YDHRtw1Hl9y3CaLZ1aP9jcHMNJdOIv6q3iVZay/ CyY9GyoRwE40+vSFAq1m355lZhCWiUa47d1D2hhDfhRRdFNKsAZrgOxBB xCNXdXr55AoiDPHhG4CpDcs20GwBLq5bMj16EfgUgXNnVXlqil8+b2ZMm ljayttnCeTUVfxNiLLgFEPaS6K7B6N8vXEVzQG9528TC462PU1J4PSHzJ g==; X-CSE-ConnectionGUID: GMMSakTvRG+HtI9KzbPdDQ== X-CSE-MsgGUID: 5wdVKI+wQIGsdOoHkk7eZA== X-IronPort-AV: E=Sophos;i="6.21,322,1763449200"; d="scan'208";a="221432061" X-Amp-Result: SKIPPED(no attachment in message) Received: from unknown (HELO email.microchip.com) ([170.129.1.10]) by esa6.microchip.iphmx.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 03 Mar 2026 11:04:44 -0700 Received: from chn-vm-ex03.mchp-main.com (10.10.87.152) by chn-vm-ex4.mchp-main.com (10.10.87.33) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.2.2562.35; Tue, 3 Mar 2026 11:04:22 -0700 Received: from bby-cbu-swbuild03.eng.microchip.com (10.10.85.11) by chn-vm-ex03.mchp-main.com (10.10.85.151) with Microsoft SMTP Server id 15.1.2507.58 via Frontend Transport; Tue, 3 Mar 2026 11:04:21 -0700 From: Charles Perry To: CC: Charles Perry , Andrew Lunn , "David S. Miller" , "Eric Dumazet" , Jakub Kicinski , Paolo Abeni , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Nicolas Ferre , Claudiu Beznea , , Subject: [PATCH net-next 3/4] net: macb: add safeguards for jumbo frame larger than 10240 Date: Tue, 3 Mar 2026 10:03:17 -0800 Message-ID: <20260303180318.1814791-4-charles.perry@microchip.com> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260303180318.1814791-1-charles.perry@microchip.com> References: <20260303180318.1814791-1-charles.perry@microchip.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain The RX buffers for GEM can have a maximum size of 16320 bytes (0xff in the RXBS field of the DMACFG register means 255*64 = 16320 bytes). The "jumbo_max_length" field (bits 0..13) of the DCFG2 register can take a value of up to 16383 (0x3FFF). This field is not used when determining the max MTU, instead an hardcoded value (jumbo_max_len) is used for each platform. Right now the maximum value for jumbo_max_len is 10240 (0x2800). GEM uses one buffer per packet which means that one buffer must allow room for the max MTU plus L2 encapsulation and alignment. This commit adds a limit to max_mtu and rx_buffer_size so that the RXBS field can never overflow when a large MTU is used. With this commit, it is now possible to add new platforms that have their gem_jumbo_max_length set to 16383. Signed-off-by: Charles Perry --- drivers/net/ethernet/cadence/macb_main.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/drivers/net/ethernet/cadence/macb_main.c b/drivers/net/ethernet/cadence/macb_main.c index c39a5a1e5732..cc48fd494458 100644 --- a/drivers/net/ethernet/cadence/macb_main.c +++ b/drivers/net/ethernet/cadence/macb_main.c @@ -50,6 +50,7 @@ struct sifive_fu540_macb_mgmt { #define MACB_RX_BUFFER_SIZE 128 #define RX_BUFFER_MULTIPLE 64 /* bytes */ +#define RX_BUFFER_MAX (0xFF * RX_BUFFER_MULTIPLE) /* 16320 bytes */ #define DEFAULT_RX_RING_SIZE 512 /* must be power of 2 */ #define MIN_RX_RING_SIZE 64 @@ -2387,7 +2388,7 @@ static void macb_init_rx_buffer_size(struct macb *bp, size_t size) if (!macb_is_gem(bp)) { bp->rx_buffer_size = MACB_RX_BUFFER_SIZE; } else { - bp->rx_buffer_size = size; + bp->rx_buffer_size = MIN(size, RX_BUFFER_MAX); if (bp->rx_buffer_size % RX_BUFFER_MULTIPLE) { netdev_dbg(bp->dev, @@ -5582,7 +5583,8 @@ static int macb_probe(struct platform_device *pdev) /* MTU range: 68 - 1518 or 10240 */ dev->min_mtu = GEM_MTU_MIN_SIZE; if ((bp->caps & MACB_CAPS_JUMBO) && bp->jumbo_max_len) - dev->max_mtu = bp->jumbo_max_len - ETH_HLEN - ETH_FCS_LEN; + dev->max_mtu = MIN(bp->jumbo_max_len, RX_BUFFER_MAX) - + ETH_HLEN - ETH_FCS_LEN; else dev->max_mtu = 1536 - ETH_HLEN - ETH_FCS_LEN; -- 2.47.3