From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eli Cohen Subject: Re: [PATCH] mlx4_en: fix transmit of packages when blue frame is enabled Date: Mon, 10 Oct 2011 11:29:26 +0200 Message-ID: <20111010092926.GO2681@mtldesk30> References: <1318145118.29415.371.camel@pasglop> <20111010084726.GM2681@mtldesk30> <1318237284.29415.422.camel@pasglop> <20111010091611.GN2681@mtldesk30> <1318238645.29415.426.camel@pasglop> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: David Laight , netdev@vger.kernel.org, Eli Cohen , linuxppc-dev@lists.ozlabs.org, Thadeu Lima de Souza Cascardo , Yevgeny Petrilin To: Benjamin Herrenschmidt Return-path: Received: from mail-bw0-f46.google.com ([209.85.214.46]:49581 "EHLO mail-bw0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753097Ab1JJJ3d (ORCPT ); Mon, 10 Oct 2011 05:29:33 -0400 Received: by mail-bw0-f46.google.com with SMTP id zt4so8238829bkb.19 for ; Mon, 10 Oct 2011 02:29:31 -0700 (PDT) Content-Disposition: inline In-Reply-To: <1318238645.29415.426.camel@pasglop> Sender: netdev-owner@vger.kernel.org List-ID: On Mon, Oct 10, 2011 at 11:24:05AM +0200, Benjamin Herrenschmidt wrote: > 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). I use the io mapping API: at driver statrt: priv->bf_mapping = io_mapping_create_wc(bf_start, bf_len); if (!priv->bf_mapping) err = -ENOMEM; and then: uar->bf_map = io_mapping_map_wc(priv->bf_mapping, uar->index << PAGE_SHIFT); Will this work on ppc? > > >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. > > > >