From mboxrd@z Thu Jan 1 00:00:00 1970 From: Wolfgang Grandegger Subject: Re: [PATCH 1/2] pch_can: Stop netif queue if last message buffer is filled Date: Tue, 21 Feb 2012 17:25:57 +0100 Message-ID: <4F43C595.8080706@grandegger.com> References: <1329840002-20746-1-git-send-email-alexander.stein@systec-electronic.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: Received: from ngcobalt02.manitu.net ([217.11.48.102]:49302 "EHLO ngcobalt02.manitu.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751232Ab2BUQ0X (ORCPT ); Tue, 21 Feb 2012 11:26:23 -0500 In-Reply-To: <1329840002-20746-1-git-send-email-alexander.stein@systec-electronic.com> Sender: linux-can-owner@vger.kernel.org List-ID: To: Alexander Stein Cc: Marc Kleine-Budde , linux-can@vger.kernel.org Hi Alexander, On 02/21/2012 05:00 PM, Alexander Stein wrote: > If all Tx buffers are empty and we start queuing frames (more than Tx > buffer size) beginning at the last message buffer we will override the > first inserted entry if it doesn't get sent meanwhile, e.g. low priority > or ACK error. There is no stop condition when all buffers are used. > We will get get awoken by pch_can_tx_complete when the last entry is sent. > > Signed-off-by: Alexander Stein > --- > drivers/net/can/pch_can.c | 4 +--- > 1 files changed, 1 insertions(+), 3 deletions(-) > > diff --git a/drivers/net/can/pch_can.c b/drivers/net/can/pch_can.c > index 6edc25e..3af5341 100644 > --- a/drivers/net/can/pch_can.c > +++ b/drivers/net/can/pch_can.c > @@ -903,9 +903,7 @@ static netdev_tx_t pch_xmit(struct sk_buff *skb, struct net_device *ndev) > > tx_obj_no = priv->tx_obj; > if (priv->tx_obj == PCH_TX_OBJ_END) { > - if (ioread32(&priv->regs->treq2) & PCH_TREQ2_TX_MASK) > - netif_stop_queue(ndev); > - > + netif_stop_queue(ndev); > priv->tx_obj = PCH_TX_OBJ_START; > } else { > priv->tx_obj++; The pch_can uses a C_CAN core (and for maintenance reasons we would like to get ride of it sooner than later). In that driver the queue is stopped here: http://lxr.linux.no/#linux+v3.2.7/drivers/net/can/c_can/c_can.c#L508 Therefore I'm not sure if your fix is enough (without looking into the manual). I could send you a "pch_pci" driver patch for C_CAN, which would allow you to use it. What kernel version are you using? Thanks, Wolfgang.