From mboxrd@z Thu Jan 1 00:00:00 1970 From: Benjamin Herrenschmidt Subject: Re: [PATCH] mlx4_en: fix transmit of packages when blue frame is enabled Date: Mon, 10 Oct 2011 11:24:05 +0200 Message-ID: <1318238645.29415.426.camel@pasglop> References: <1318145118.29415.371.camel@pasglop> <20111010084726.GM2681@mtldesk30> <1318237284.29415.422.camel@pasglop> <20111010091611.GN2681@mtldesk30> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: David Laight , netdev@vger.kernel.org, Eli Cohen , linuxppc-dev@lists.ozlabs.org, Thadeu Lima de Souza Cascardo , Yevgeny Petrilin To: Eli Cohen Return-path: Received: from gate.crashing.org ([63.228.1.57]:33584 "EHLO gate.crashing.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752944Ab1JJJY1 (ORCPT ); Mon, 10 Oct 2011 05:24:27 -0400 In-Reply-To: <20111010091611.GN2681@mtldesk30> Sender: netdev-owner@vger.kernel.org List-ID: On Mon, 2011-10-10 at 11:16 +0200, Eli Cohen wrote: > Until then I think we need to have the logic working right on ppc and > measure if blue flame buys us any improvement in ppc. If that's not > the case (e.g because write combining is not working), then maybe we > should avoid using blueflame in ppc. > Could any of the guys from IBM check this and give us feedback? I don't have the necessary hardware myself to test that but maybe Thadeu can. Note that for WC to work, things must be mapped non-guarded. You can do that by using ioremap_prot() with pgprot_noncached_wc(PAGE_KERNEL) or ioremap_wc() (dunno how "generic" the later is). >>From there, you should get write combining provided that you don't have barriers between every access (ie those copy operations in their current form should do the trick). Cheers, Ben. > > Maybe it's time for us to revive those discussions about providing a > > good set of relaxed MMIO accessors with explicit barriers :-) > > > > Cheers, > > Ben. > >