From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-189.mta1.migadu.com (out-189.mta1.migadu.com [95.215.58.189]) (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 3D8D626B2AD for ; Mon, 30 Mar 2026 18:50:14 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.189 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774896616; cv=none; b=PSwWuO/0stwu7mOaUrTC35xrRtwLMsNH/W/EIIY9pAqvIBs30F9KMvlG25NPropj9eE5o6iZ0+ShesRPoGqfK3avrQKPA9IX99gjmNI4Zh9mKoUeZ9QYTPlS2jnM3xBBBOgxhemb3k2hxh5K4LsOmmN2ROvBWjfQAIXXwylLhTg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774896616; c=relaxed/simple; bh=QsrmC22upVvQWb1ttkE2gs6nFEWpOFmpRk7fl+hFzkY=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=nEsUu4XhQ3+WKeBGr2tGYCjOih3SMPA1+97WurHAZaku966TX9bgVysoRjQQA/cn0KoDjJEe59jaK/M1lE1v/CRYIRnfIr8w634Ppvn398HM1dUs9CLHmx6RpY0zfTyoQNxNYUIKXVBVLftyTQCf9E4QsWv+N8J5pjOs5rMD3Ns= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=dXamNKUK; arc=none smtp.client-ip=95.215.58.189 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="dXamNKUK" Message-ID: <8a57e85b-8917-48b8-9412-b10a38fa230b@linux.dev> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1774896612; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=ZbI/xWQ/rrC6wAb85E1XodfYiivSfrUvb5aJFFUK0R4=; b=dXamNKUKlXf3V7TOgKCvckNA8R4hlEefGV1lkULsTRrQwPcO2HWM0lPy99bob7KpucHVR2 /8gwDkVk+iRKYIITKU+oy1ANThY8TLqSVDzZVX4hMvZS5Rr2cSLcS00JMdKNC/JI5oV52B Z4J7fYAAc5CJeelap4+eCNbFtAmW+oU= Date: Mon, 30 Mar 2026 14:49:59 -0400 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Subject: Re: [PATCH net V2 2/2] net: xilinx: axienet: Fix BQL accounting for multi-BD TX packets To: Suraj Gupta , Radhey Shyam Pandey , Andrew Lunn , "David S . Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni Cc: Michal Simek , Daniel Borkmann , Ariane Keller , netdev@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org References: <20260327073238.134948-1-suraj.gupta2@amd.com> <20260327073238.134948-3-suraj.gupta2@amd.com> Content-Language: en-US X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Sean Anderson In-Reply-To: <20260327073238.134948-3-suraj.gupta2@amd.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT On 3/27/26 03:32, Suraj Gupta wrote: > When a TX packet spans multiple buffer descriptors (scatter-gather), > axienet_free_tx_chain sums the per-BD actual length from descriptor > status into a caller-provided accumulator. That sum is reset on each > NAPI poll. If the BDs for a single packet complete across different > polls, the earlier bytes are lost and never credited to BQL. This > causes BQL to think bytes are permanently in-flight, eventually > stalling the TX queue. > > The SKB pointer is stored only on the last BD of a packet. When that > BD completes, use skb->len for the byte count instead of summing > per-BD status lengths. This matches netdev_sent_queue(), which debits > skb->len, and naturally survives across polls because no partial > packet contributes to the accumulator. > > Fixes: c900e49d58eb ("net: xilinx: axienet: Implement BQL") > Signed-off-by: Suraj Gupta > --- > drivers/net/ethernet/xilinx/xilinx_axienet_main.c | 9 ++++----- > 1 file changed, 4 insertions(+), 5 deletions(-) > > diff --git a/drivers/net/ethernet/xilinx/xilinx_axienet_main.c b/drivers/net/ethernet/xilinx/xilinx_axienet_main.c > index b06e4c37ff61..263c4b67fd5a 100644 > --- a/drivers/net/ethernet/xilinx/xilinx_axienet_main.c > +++ b/drivers/net/ethernet/xilinx/xilinx_axienet_main.c > @@ -770,8 +770,8 @@ static int axienet_device_reset(struct net_device *ndev) > * @first_bd: Index of first descriptor to clean up > * @nr_bds: Max number of descriptors to clean up > * @force: Whether to clean descriptors even if not complete > - * @sizep: Pointer to a u32 filled with the total sum of all bytes > - * in all cleaned-up descriptors. Ignored if NULL. > + * @sizep: Pointer to a u32 accumulating the total byte count of > + * completed packets (using skb->len). Ignored if NULL. > * @budget: NAPI budget (use 0 when not called from NAPI poll) > * > * Would either be called after a successful transmit operation, or after > @@ -805,6 +805,8 @@ static int axienet_free_tx_chain(struct axienet_local *lp, u32 first_bd, > DMA_TO_DEVICE); > > if (cur_p->skb && (status & XAXIDMA_BD_STS_COMPLETE_MASK)) { > + if (sizep) > + *sizep += cur_p->skb->len; > napi_consume_skb(cur_p->skb, budget); > packets++; > } > @@ -818,9 +820,6 @@ static int axienet_free_tx_chain(struct axienet_local *lp, u32 first_bd, > wmb(); > cur_p->cntrl = 0; > cur_p->status = 0; > - > - if (sizep) > - *sizep += status & XAXIDMA_BD_STS_ACTUAL_LEN_MASK; > } > > if (!force) { Reviewed-by: Sean Anderson Although FWIW this may result in slightly-different statistics. Not sure if we care since this will only affect packets that could not be sent for whatever reason (collisions, loss of carrier, etc.)