From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ralf Baechle Subject: Re: [PATCH] e100: Add missing dma sync for proper operation with non-coherent caches. Date: Tue, 26 Aug 2008 23:49:16 +0100 Message-ID: <20080826224916.GB8838@linux-mips.org> References: <48B3A8D0.2040108@avtrex.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: e1000-devel@lists.sourceforge.net, netdev@vger.kernel.org, linux-mips To: David Daney Return-path: Content-Disposition: inline In-Reply-To: <48B3A8D0.2040108@avtrex.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: e1000-devel-bounces@lists.sourceforge.net Errors-To: e1000-devel-bounces@lists.sourceforge.net List-Id: netdev.vger.kernel.org On Mon, Aug 25, 2008 at 11:55:12PM -0700, David Daney wrote: > I am running the e100 driver on a MIPS 4KEc system (32 bit mips with > non-coherent DMA). There was a problem where received packets would > get 'stuck' for several seconds at a time and then be released all at > once. > > The cause was that if an interrupt were received when no RX packets > were available, the status for the receive buffer would be stuck in > the cache, so when the next interrupt arrived the old status value was > read (indicating no packets available) instead of the new value. > > The fix is to call pci_dma_sync_single_for_device on the RX if the > packet is not available to invalidate the cache so that at the next > interrupt valid status is returned. > > The driver currently calls pci_dma_sync_single_for_cpu before reading > the status, and this is indeed needed for cases like the R10000 CPU > where the cache can be polluted by speculative execution, but for most > machines it is a nop. > > The patch was tested on 2.6.17-rc4 on a MIPS 4KEc. > > Signed-off-by: David Daney Makes sense to me. Reviewed-by: Ralf Baechle Ralf ------------------------------------------------------------------------- This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK & win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100&url=/