From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Subject: Re: NIU driver: Sun x8 Express Quad Gigabit Ethernet Adapter Date: Wed, 12 Nov 2008 04:11:43 -0800 (PST) Message-ID: <20081112.041143.11487260.davem@davemloft.net> References: <20081112.014923.68124784.davem@davemloft.net> <1226487710.6834.53.camel@localhost.localdomain> <20081112.035240.226243372.davem@davemloft.net> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org To: jdb@comx.dk Return-path: Received: from 74-93-104-97-Washington.hfc.comcastbusiness.net ([74.93.104.97]:50302 "EHLO sunset.davemloft.net" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1751525AbYKLMLn (ORCPT ); Wed, 12 Nov 2008 07:11:43 -0500 In-Reply-To: <20081112.035240.226243372.davem@davemloft.net> Sender: netdev-owner@vger.kernel.org List-ID: From: David Miller Date: Wed, 12 Nov 2008 03:52:40 -0800 (PST) > Ok, Jesper, please try two things for me, leave the debugging patch > in there for all the tests: > > 1) Retrigger the problem (with or without MSI, doesn't matter) but > add back in that test I asked you to try last week. The one > where the "if (++rp->mark_counter == rp->mark_freq)" condition > test in niu_start_xmit() is commented out, so that the > "mrk |= TX_DESC_MARK;" statement always runs. > > Get me the log dump produced by that scenerio. > > 2) Next, simply comment out the: > > if (unlikely(!(cs & (TX_CS_MK | TX_CS_MMK)))) > goto out; > > lines in niu_tx_work(). > > Let's see what new info we can get out of this. These tests are still useful for me, so please perform them, but I think I've found the bug. I am guessing you're running a 32-bit x86 kernel. In such a case the driver has to define a local readq() and writeq() implementation. What I provide for NIU right now reads the upper 32-bits then the lower 32-bits of the register. Guess what that does? The packet counters live in the upper 32-bits and the MARK bits live in the lower 32-bits of the TX_CS register. So it first reads the packet counters, and as a side effect that clears the MARK bits in the TX_CS register. So when we read the lower 32-bits the MARK bits are always seen as zero. BzzaaarT! So the following patch should fix this bug. writeq() should be OK as-is, so doesn't need a similar change. diff --git a/drivers/net/niu.c b/drivers/net/niu.c index 9acb5d7..d8463b1 100644 --- a/drivers/net/niu.c +++ b/drivers/net/niu.c @@ -51,8 +51,7 @@ MODULE_VERSION(DRV_MODULE_VERSION); #ifndef readq static u64 readq(void __iomem *reg) { - return (((u64)readl(reg + 0x4UL) << 32) | - (u64)readl(reg)); + return ((u64) readl(reg)) | (((u64) readl(reg + 4UL)) << 32); } static void writeq(u64 val, void __iomem *reg)