From mboxrd@z Thu Jan 1 00:00:00 1970 From: Benjamin Herrenschmidt Subject: [PATCH v2 8/9] ftgmac100: Fix potential ordering issue in NAPI poll Date: Thu, 13 Apr 2017 14:39:15 +1000 Message-ID: <20170413043916.7793-9-benh@kernel.crashing.org> References: <20170413043916.7793-1-benh@kernel.crashing.org> Cc: Benjamin Herrenschmidt To: netdev@vger.kernel.org Return-path: Received: from gate.crashing.org ([63.228.1.57]:57834 "EHLO gate.crashing.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755988AbdDMEkE (ORCPT ); Thu, 13 Apr 2017 00:40:04 -0400 In-Reply-To: <20170413043916.7793-1-benh@kernel.crashing.org> Sender: netdev-owner@vger.kernel.org List-ID: We need to ensure the loads from the descriptor are done after the MMIO store clearing the interrupts has completed, otherwise we might still miss work. A read back from the MMIO register will "push" the posted store and ioread32 has a barrier on weakly aordered architectures that will order subsequent accesses. Signed-off-by: Benjamin Herrenschmidt --- drivers/net/ethernet/faraday/ftgmac100.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/drivers/net/ethernet/faraday/ftgmac100.c b/drivers/net/ethernet/faraday/ftgmac100.c index 71763e4..9b7a24e 100644 --- a/drivers/net/ethernet/faraday/ftgmac100.c +++ b/drivers/net/ethernet/faraday/ftgmac100.c @@ -1347,6 +1347,13 @@ static int ftgmac100_poll(struct napi_struct *napi, int budget) */ iowrite32(FTGMAC100_INT_RXTX, priv->base + FTGMAC100_OFFSET_ISR); + + /* Push the above (and provides a barrier vs. subsequent + * reads of the descriptor). + */ + ioread32(priv->base + FTGMAC100_OFFSET_ISR); + + /* Check RX and TX descriptors for more work to do */ if (ftgmac100_check_rx(priv) || ftgmac100_tx_buf_cleanable(priv)) return budget; -- 2.9.3