From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from az33egw02.freescale.net (az33egw02.freescale.net [192.88.158.103]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client CN "az33egw02.freescale.net", Issuer "Thawte Premium Server CA" (verified OK)) by ozlabs.org (Postfix) with ESMTP id 195B0DDF74 for ; Thu, 3 May 2007 05:57:22 +1000 (EST) Date: Wed, 2 May 2007 14:57:12 -0500 From: Scott Wood To: jgarzik@pobox.com Subject: [PATCH v2] gianfar: Add I/O barriers when touching buffer descriptor ownership. Message-ID: <20070502195712.GA16541@ld0162-tx32.am.freescale.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: netdev@vger.kernel.org, linuxppc-dev@ozlabs.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , The hardware must not see that is given ownership of a buffer until it is completely written, and when the driver receives ownership of a buffer, it must ensure that any other reads to the buffer reflect its final state. Thus, I/O barriers are added where required. Without this patch, I have observed GCC reordering the setting of bdp->length and bdp->status in gfar_new_skb. Signed-off-by: Scott Wood --- This is version 2 of this patch. I was told that eieio doesn't order loads from main memory, so a sync is used instead. Also, due to objectons that iobarrier_* shouldn't be used for main memory, I used eieio() instead (a wmb() would be unnecessarily heavy). drivers/net/gianfar.c | 3 +++ 1 files changed, 3 insertions(+), 0 deletions(-) diff --git a/drivers/net/gianfar.c b/drivers/net/gianfar.c index b666a0c..b014d27 100644 --- a/drivers/net/gianfar.c +++ b/drivers/net/gianfar.c @@ -1025,6 +1025,7 @@ static int gfar_start_xmit(struct sk_buff *skb, struct net_device *dev) dev->trans_start = jiffies; + eieio(); txbdp->status = status; /* If this was the last BD in the ring, the next one */ @@ -1301,6 +1302,7 @@ struct sk_buff * gfar_new_skb(struct net_device *dev, struct rxbd8 *bdp) bdp->length = 0; /* Mark the buffer empty */ + eieio(); bdp->status |= (RXBD_EMPTY | RXBD_INTERRUPT); return skb; @@ -1484,6 +1486,7 @@ int gfar_clean_rx_ring(struct net_device *dev, int rx_work_limit) bdp = priv->cur_rx; while (!((bdp->status & RXBD_EMPTY) || (--rx_work_limit < 0))) { + rmb(); skb = priv->rx_skbuff[priv->skb_currx]; if (!(bdp->status & -- 1.5.0.3