From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail.tipi-net.de (mail.tipi-net.de [194.13.80.246]) (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 3683D29E116; Fri, 13 Mar 2026 12:45:40 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=194.13.80.246 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773405943; cv=none; b=Lj4xBMSJhWBhxY66QKCC5Sc14f+teLCEQ42/wUAbe86XfNx6bkoR35cCcRCXTGeYWr2yNvqA6GWhR2IBIqls4uuJUYnZSlwibjHeoZL8PlxBSMj8cgx3up5oKzvr7iVsOQcoBHPqemSQLhNXSqC/5CSbU9rim68nmDoWciZU7Rs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773405943; c=relaxed/simple; bh=Ekj7aRQNWx1AZSY3KviItzQEDlkzGy0tWmfbcRdwtV4=; h=MIME-Version:Date:From:To:Cc:Subject:In-Reply-To:References: Message-ID:Content-Type; b=XKGIv6PvBQywU3QyglPUXgwnDbOwTQJjgpIFD6SqgUUC1+ziq4rwRE9M7Um7kkVQ6ontkGNMSRVlQBUqBTdhZ6cqwNX3djWU38ByUZNJWQRyTzsitumEl5DWojLRQhRUo6XjHvg2m0O2owOF9N6O8WovL9xT7NFzq6aZVIManrs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=tipi-net.de; spf=pass smtp.mailfrom=tipi-net.de; dkim=pass (2048-bit key) header.d=tipi-net.de header.i=@tipi-net.de header.b=X5Z6kWzV; arc=none smtp.client-ip=194.13.80.246 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=tipi-net.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=tipi-net.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=tipi-net.de header.i=@tipi-net.de header.b="X5Z6kWzV" Received: from [127.0.0.1] (localhost [127.0.0.1]) by localhost (Mailerdaemon) with ESMTPSA id 23C62A002C; Fri, 13 Mar 2026 13:45:33 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=tipi-net.de; s=dkim; t=1773405937; h=from:subject:date:message-id:to:cc:mime-version:content-type: content-transfer-encoding:in-reply-to:references; bh=A/47jnKZviCg6uCxxtHoDQRxJVDuZQz5+RJqU7FcO/c=; b=X5Z6kWzVrRPMiOriiFH6ZhD6TV95cqwr+aJEyqjlunKJoxz4c10Ol6ykL5j3nnILphpBEM 8SNm7q1JtINj1RUtIoRYdlUwq/A0eUGdyIGj4IMmDdaR7UYW1sAU7oxLO+Mqlbd2OixdXT LQUcZQ3W9zFHwgdYZJHh8BdHH6V1hbU3BRIzoLaVSmZiW296Yu8FuJMNZs46iAjf7TmEDI 9sc3jjRADpB/BqXeSJowFt7yO07smy8voT+akZDKyXbHbUzYV/VHdNzlQLpqmV8Oe+d1uu 91NN33rrGcX6WD09sR/zsubqMR0KD5Rod4C2c83UEa2pMFye/x1enn4mSiaDTw== Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Date: Fri, 13 Mar 2026 13:45:33 +0100 From: Nicolai Buchwitz To: Subbaraya Sundeep Cc: Andrew Lunn , "David S . Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Doug Berger , Florian Fainelli , Broadcom internal kernel review list , Vikas Gupta , Bhargava Marreddy , Rajashekar Hudumula , Eric Biggers , Heiner Kallweit , =?UTF-8?Q?Markus_Bl=C3=B6chl?= , Arnd Bergmann , netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH net-next 4/6] net: bcmgenet: add XDP_TX support In-Reply-To: <20260313113737.GA209052@kernel-ep2> References: <20260313092101.1344954-1-nb@tipi-net.de> <20260313092101.1344954-5-nb@tipi-net.de> <20260313113737.GA209052@kernel-ep2> Message-ID: <5cb0916bdb19ea33e11ea93f7174fd76@tipi-net.de> X-Sender: nb@tipi-net.de Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 7bit X-Last-TLS-Session-Version: TLSv1.3 On 13.3.2026 12:37, Subbaraya Sundeep wrote: > Hi, Hi Sundeep > > On 2026-03-13 at 14:50:59, Nicolai Buchwitz (nb@tipi-net.de) wrote: >> Implement XDP_TX by submitting XDP frames through the default TX ring >> (DESC_INDEX). The frame is DMA-mapped and placed into a single TX >> descriptor with SOP|EOP|APPEND_CRC flags. >> >> The xdp_frame pointer is stored in the TX control block so that >> bcmgenet_free_tx_cb() can call xdp_return_frame() on TX completion, >> returning the page to the originating page_pool. >> >> The page_pool DMA direction is changed from DMA_FROM_DEVICE to >> DMA_BIDIRECTIONAL to support the TX DMA mapping of received pages. >> >> Signed-off-by: Nicolai Buchwitz >> --- >> .../net/ethernet/broadcom/genet/bcmgenet.c | 73 >> ++++++++++++++++++- >> .../net/ethernet/broadcom/genet/bcmgenet.h | 1 + >> 2 files changed, 71 insertions(+), 3 deletions(-) >> >> diff --git a/drivers/net/ethernet/broadcom/genet/bcmgenet.c >> b/drivers/net/ethernet/broadcom/genet/bcmgenet.c >> index d43729fc2b1b..373ba5878ca1 100644 >> --- a/drivers/net/ethernet/broadcom/genet/bcmgenet.c >> +++ b/drivers/net/ethernet/broadcom/genet/bcmgenet.c >> @@ -1893,6 +1893,12 @@ static struct sk_buff >> *bcmgenet_free_tx_cb(struct device *dev, >> if (cb == GENET_CB(skb)->last_cb) >> return skb; >> >> + } else if (cb->xdpf) { >> + dma_unmap_single(dev, dma_unmap_addr(cb, dma_addr), >> + dma_unmap_len(cb, dma_len), DMA_TO_DEVICE); >> + dma_unmap_addr_set(cb, dma_addr, 0); >> + xdp_return_frame(cb->xdpf); >> + cb->xdpf = NULL; >> } else if (dma_unmap_addr(cb, dma_addr)) { >> dma_unmap_page(dev, >> dma_unmap_addr(cb, dma_addr), >> @@ -2299,10 +2305,62 @@ static struct sk_buff >> *bcmgenet_xdp_build_skb(struct bcmgenet_rx_ring *ring, >> return skb; >> } >> >> +static bool bcmgenet_xdp_xmit_frame(struct bcmgenet_priv *priv, >> + struct xdp_frame *xdpf) >> +{ >> + struct bcmgenet_tx_ring *ring = &priv->tx_rings[DESC_INDEX]; >> + struct device *kdev = &priv->pdev->dev; >> + struct enet_cb *tx_cb_ptr; >> + dma_addr_t mapping; >> + u32 len_stat; >> + >> + spin_lock(&ring->lock); >> + >> + if (ring->free_bds < 1) { >> + spin_unlock(&ring->lock); >> + return false; >> + } >> + >> + tx_cb_ptr = bcmgenet_get_txcb(priv, ring); >> + >> + mapping = dma_map_single(kdev, xdpf->data, xdpf->len, >> DMA_TO_DEVICE); > > AFAIU you are transmitting the frame received on a RQ which is from the > page pool > and already dma mapped. Do you have to do dma_map again? > > Thanks, > Sundeep > You're right. Since the page_pool is configured with DMA_BIDIRECTIONAL, the pages are already mapped and we can reuse the existing mapping for XDP_TX frames. The initial implementation took the simple route of mapping everything uniformly, but that's unnecessary overhead for the local XDP_TX case. In v2 I'll add a bool dma_map parameter to bcmgenet_xdp_xmit_frame() (following the mvneta/stmmac pattern): XDP_TX will reuse the page_pool mapping via page_pool_get_dma_addr() + dma_sync_single_for_device(), while ndo_xdp_xmit will keep dma_map_single() for foreign frames. The cleanup path will be split accordingly. Regards Nicolai >> [...]