From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 EB76A329C43; Mon, 27 Oct 2025 19:28:47 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761593328; cv=none; b=nWH2cffYV1sb65k6dNsjx4oaAhXfuB4Z0vvqrUvH46EMe9yOimJm7vQfGi+MeQO1NjlWp3M5KRLZ70WkXXpevAuaBZQdOgXS5UrlDKlMGbUbG5ulZM/b8T1/qnKlx1cVBlcncJEzdNKbKmOvi0X2zzp+E91h+WKuwYFy5Ji0Pao= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761593328; c=relaxed/simple; bh=4cy9J1q5g8IHSoFogXYOXF8CqlbO4hzRslj73B2HHl8=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=WUneqsCEzdx+gHqJtlk4ttVwHNrPhkjjbxs31wppkcZtGNTUi3lxQx8fzj5xOA5zjixVokF/DV561uhVDjPovwpju/VSv2X+2Bo2DOH5yhVhgQm+YJWuw9gEZO4Ms6SQ985ZTTVZ5dF5dyiwi2WOLI9mAEn9Nc6MeejdgUxYbxA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=bWsBTGTY; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="bWsBTGTY" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E17CEC4CEF1; Mon, 27 Oct 2025 19:28:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1761593327; bh=4cy9J1q5g8IHSoFogXYOXF8CqlbO4hzRslj73B2HHl8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=bWsBTGTYhvMQyYTZGJnDbaNzVo/rXgRJe2WwTZJSLHomgYKl+T47HUqKLd57t7dwM FpcW+bVKGFkjSJtKZ/5BtfKZYtBqCt1HgJe5Yj+lcH0ZFer+8H4EMuiyDfcVQ1dcfn v8XKFKzLeNFxbyKSqg+30ry+ZA6XUhF1hCRcasdI= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Fabrizio Castro , Lad Prabhakar , =?UTF-8?q?Niklas=20S=C3=B6derlund?= , Jakub Kicinski Subject: [PATCH 6.17 099/184] net: ravb: Enforce descriptor type ordering Date: Mon, 27 Oct 2025 19:36:21 +0100 Message-ID: <20251027183517.578591273@linuxfoundation.org> X-Mailer: git-send-email 2.51.1 In-Reply-To: <20251027183514.934710872@linuxfoundation.org> References: <20251027183514.934710872@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 6.17-stable review patch. If anyone has any objections, please let me know. ------------------ From: Lad Prabhakar commit 5370c31e84b0e0999c7b5ff949f4e104def35584 upstream. Ensure the TX descriptor type fields are published in a safe order so the DMA engine never begins processing a descriptor chain before all descriptor fields are fully initialised. For multi-descriptor transmits the driver writes DT_FEND into the last descriptor and DT_FSTART into the first. The DMA engine begins processing when it observes DT_FSTART. Move the dma_wmb() barrier so it executes immediately after DT_FEND and immediately before writing DT_FSTART (and before DT_FSINGLE in the single-descriptor case). This guarantees that all prior CPU writes to the descriptor memory are visible to the device before DT_FSTART is seen. This avoids a situation where compiler/CPU reordering could publish DT_FSTART ahead of DT_FEND or other descriptor fields, allowing the DMA to start on a partially initialised chain and causing corrupted transmissions or TX timeouts. Such a failure was observed on RZ/G2L with an RT kernel as transmit queue timeouts and device resets. Fixes: 2f45d1902acf ("ravb: minimize TX data copying") Cc: stable@vger.kernel.org Co-developed-by: Fabrizio Castro Signed-off-by: Fabrizio Castro Signed-off-by: Lad Prabhakar Reviewed-by: Niklas Söderlund Link: https://patch.msgid.link/20251017151830.171062-4-prabhakar.mahadev-lad.rj@bp.renesas.com Signed-off-by: Jakub Kicinski Signed-off-by: Greg Kroah-Hartman --- drivers/net/ethernet/renesas/ravb_main.c | 16 ++++++++++++++-- 1 file changed, 14 insertions(+), 2 deletions(-) --- a/drivers/net/ethernet/renesas/ravb_main.c +++ b/drivers/net/ethernet/renesas/ravb_main.c @@ -2210,13 +2210,25 @@ static netdev_tx_t ravb_start_xmit(struc skb_tx_timestamp(skb); } - /* Descriptor type must be set after all the above writes */ - dma_wmb(); + if (num_tx_desc > 1) { desc->die_dt = DT_FEND; desc--; + /* When using multi-descriptors, DT_FEND needs to get written + * before DT_FSTART, but the compiler may reorder the memory + * writes in an attempt to optimize the code. + * Use a dma_wmb() barrier to make sure DT_FEND and DT_FSTART + * are written exactly in the order shown in the code. + * This is particularly important for cases where the DMA engine + * is already running when we are running this code. If the DMA + * sees DT_FSTART without the corresponding DT_FEND it will enter + * an error condition. + */ + dma_wmb(); desc->die_dt = DT_FSTART; } else { + /* Descriptor type must be set after all the above writes */ + dma_wmb(); desc->die_dt = DT_FSINGLE; } ravb_modify(ndev, TCCR, TCCR_TSRQ0 << q, TCCR_TSRQ0 << q);