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=-15.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=ham 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 16452C11F65 for ; Wed, 30 Jun 2021 06:13:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DEBD361CEF for ; Wed, 30 Jun 2021 06:13:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232235AbhF3GQM (ORCPT ); Wed, 30 Jun 2021 02:16:12 -0400 Received: from mga06.intel.com ([134.134.136.31]:34424 "EHLO mga06.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229933AbhF3GQK (ORCPT ); Wed, 30 Jun 2021 02:16:10 -0400 X-IronPort-AV: E=McAfee;i="6200,9189,10030"; a="269428900" X-IronPort-AV: E=Sophos;i="5.83,311,1616482800"; d="scan'208";a="269428900" Received: from orsmga007.jf.intel.com ([10.7.209.58]) by orsmga104.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 29 Jun 2021 23:13:41 -0700 X-IronPort-AV: E=Sophos;i="5.83,311,1616482800"; d="scan'208";a="447342239" Received: from sneftin-mobl.ger.corp.intel.com (HELO [10.185.169.66]) ([10.185.169.66]) by orsmga007-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 29 Jun 2021 23:13:38 -0700 Subject: Re: [Intel-wired-lan] [PATCH] driver core: fix e1000e ltr bug To: Yee Li Cc: jesse.brandeburg@intel.com, anthony.l.nguyen@intel.com, davem@davemloft.net, kuba@kernel.org, intel-wired-lan@lists.osuosl.org, linux-kernel@vger.kernel.org, "Ruinskiy, Dima" , "Edri, Michael" , "Efrati, Nir" References: <20210629082128.255988-1-seven.yi.lee@gmail.com> <02ff77ef-e802-8e13-d169-1ab2c250405a@intel.com> From: "Neftin, Sasha" Message-ID: <0234b97a-f207-47b0-1545-582ee5282824@intel.com> Date: Wed, 30 Jun 2021 09:13:36 +0300 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 6/29/2021 20:33, Yee Li wrote: > > Yes, 18874368ns > 3145728ns. > But, 0xe40 < 0x1003. I got you. I would agree, direct comparison is error-prone. (10M is impacted) I would suggest do not use convert function. lat_en should rather presented as lat_enc = scale x value: Introduce two u16 variables, u16 lat_enc_d and u16 max_ltr_enc_d; lat_enc_d = (lat_enc & 0x0x3ff) x (1U << 5*((max_ltr_enc & 0x1c00) >> 10)) max_ltr_enc_d = (max_ltr_enc & 0x0x3ff) x (1U << 5*((max_ltr_enc & 0x1c00) >> 10)) Then: if (lat_enc_d > max_ltr_enc_d) lat_enc = max_ltr_enc; what do you think? > > So, the final lat_enc is 0xe40. > (Latency encoded is less than maximum LTR encoded by platform) > > Neftin, Sasha > > 于 2021年6月29日周二 22:49写道： > > On 6/29/2021 11:21, YeeLi wrote: > Yeeli, > > In e1000e driver, a PCIe-like device, the max snoop/no-snoop latency > > is the upper limit.So, directly compare the size of lat_enc and > > max_ltr_enc is incorrect. > > > why? > >      In 1000Mbps, 0x8b9 < 0x1003, 189440 ns < 3145728 ns, correct. > > > >      In 100Mbps, 0xc3a < 0x1003, 1900544 ns < 3145728 ns, correct. > > > >      In 10Mbps, 0xe40 < 0x1003, 18874368 > 3145728, incorrect. > > > Platform LTR encoded is 0x1003 - right. It is meant 1048576ns x 3 = > 3145738ns. > Now, > for 1000M: 0x08b9 => 185ns x 1024 = 189440ns (you are correct) > for 100M: 0x0c3a => 58ns x 32768 = 1900544ns (correct) > for 10M: 0x0e41 => 577ns x 32768 = 18907136ns (ok?) > 18907136ns > 3145738ns, (latency encoded is great than maximum LTR > encoded by platform) - so, there is no point to wait more than platform > required, and lat_enc=max_ltr_enc. It is expected and we sent right > value to the power management controller. > What is the problem you try solve? > > > Decoded the lat_enc and max_ltr_enc before compare them is necessary. > > > > Signed-off-by: YeeLi > > > --- > >   drivers/net/ethernet/intel/e1000e/ich8lan.c | 23 > ++++++++++++++++++++- > >   1 file changed, 22 insertions(+), 1 deletion(-) > > > > diff --git a/drivers/net/ethernet/intel/e1000e/ich8lan.c > b/drivers/net/ethernet/intel/e1000e/ich8lan.c > > index 590ad110d383..3bff1b570b76 100644 > > --- a/drivers/net/ethernet/intel/e1000e/ich8lan.c > > +++ b/drivers/net/ethernet/intel/e1000e/ich8lan.c > > @@ -986,6 +986,27 @@ static s32 e1000_k1_workaround_lpt_lp(struct > e1000_hw *hw, bool link) > >       return ret_val; > >   } > > > > +static u32 convert_e1000e_ltr_scale(u32 val) > > +{ > > +     if (val > 5) > > +             return 0; > > + > > +     return 1U << (5 * val); > > +} > > + > > +static u64 decoded_ltr(u32 val) > > +{ > > +     u64 decoded_latency; > > +     u32 value; > > +     u32 scale; > > + > > +     value = val & 0x03FF; > > +     scale = (val & 0x1C00) >> 10; > > +     decoded_latency = value * convert_e1000e_ltr_scale(scale); > > + > > +     return decoded_latency; > > +} > > + > >   /** > >    *  e1000_platform_pm_pch_lpt - Set platform power management > values > >    *  @hw: pointer to the HW structure > > @@ -1059,7 +1080,7 @@ static s32 e1000_platform_pm_pch_lpt(struct > e1000_hw *hw, bool link) > >                                    E1000_PCI_LTR_CAP_LPT + 2, > &max_nosnoop); > >               max_ltr_enc = max_t(u16, max_snoop, max_nosnoop); > > > > -             if (lat_enc > max_ltr_enc) > > +             if (decoded_ltr(lat_enc) > decoded_ltr(max_ltr_enc)) > >                       lat_enc = max_ltr_enc; > >       } > > > > > sasha >