From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.7 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2FECDC432C2 for ; Wed, 25 Sep 2019 12:01:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 00D5121D7C for ; Wed, 25 Sep 2019 12:01:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2405209AbfIYMB1 (ORCPT ); Wed, 25 Sep 2019 08:01:27 -0400 Received: from shards.monkeyblade.net ([23.128.96.9]:34902 "EHLO shards.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730396AbfIYMB1 (ORCPT ); Wed, 25 Sep 2019 08:01:27 -0400 Received: from localhost (unknown [65.39.69.237]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (Client did not present a certificate) (Authenticated sender: davem-davemloft) by shards.monkeyblade.net (Postfix) with ESMTPSA id AA024154ECD62; Wed, 25 Sep 2019 05:01:24 -0700 (PDT) Date: Wed, 25 Sep 2019 14:01:22 +0200 (CEST) Message-Id: <20190925.140122.1211987325360902544.davem@davemloft.net> To: Jose.Abreu@synopsys.com Cc: thierry.reding@gmail.com, peppe.cavallaro@st.com, alexandre.torgue@st.com, f.fainelli@gmail.com, jonathanh@nvidia.com, bbiswas@nvidia.com, netdev@vger.kernel.org, linux-tegra@vger.kernel.org Subject: Re: [PATCH v3 0/2] net: stmmac: Enhanced addressing mode for DWMAC 4.10 From: David Miller In-Reply-To: References: <20190925.133353.1445361137776125638.davem@davemloft.net> X-Mailer: Mew version 6.8 on Emacs 26.2 Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.5.12 (shards.monkeyblade.net [149.20.54.216]); Wed, 25 Sep 2019 05:01:26 -0700 (PDT) Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org From: Jose Abreu Date: Wed, 25 Sep 2019 11:41:04 +0000 > From: David Miller > Date: Sep/25/2019, 12:33:53 (UTC+00:00) > >> From: Jose Abreu >> Date: Wed, 25 Sep 2019 10:44:53 +0000 >> >> > From: David Miller >> > Date: Sep/24/2019, 20:45:08 (UTC+00:00) >> > >> >> From: Thierry Reding >> >> Date: Fri, 20 Sep 2019 19:00:34 +0200 >> >> >> >> Also, you're now writing to the high 32-bits unconditionally, even when >> >> it will always be zero because of 32-bit addressing. That looks like >> >> a step backwards to me. >> > >> > Don't agree. As per previous discussions and as per my IP knowledge, if >> > EAME is not enabled / not supported the register can still be written. >> > This is not fast path and will not impact any remaining operation. Can >> > you please explain what exactly is the concern about this ? >> > >> > Anyway, this is an important feature for performance so I hope Thierry >> > re-submits this once -next opens and addressing the review comments. >> >> Perhaps I misunderstand the context, isn't this code writing the >> descriptors for every packet? > > No, its just setting up the base address for the descriptors which is > done in open(). The one that's in the fast path is the tail address, > which is always the lower 32 bits. Aha, ok, yes then initializing both parts unconditionally is fine.