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=-2.3 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 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 3355AC432C2 for ; Wed, 25 Sep 2019 17:31:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id EF092214DA for ; Wed, 25 Sep 2019 17:31:18 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="Ye2CbRFR" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2634176AbfIYRbS (ORCPT ); Wed, 25 Sep 2019 13:31:18 -0400 Received: from mail-pg1-f196.google.com ([209.85.215.196]:44837 "EHLO mail-pg1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725955AbfIYRbS (ORCPT ); Wed, 25 Sep 2019 13:31:18 -0400 Received: by mail-pg1-f196.google.com with SMTP id g3so197790pgs.11; Wed, 25 Sep 2019 10:31:17 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=subject:to:cc:references:from:openpgp:autocrypt:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=GECBsDviO4R03B/RCsfVCSEdE0MlOr5oah5nwGqAhaM=; b=Ye2CbRFRK+bj0HJmEfrKPJba37xlaeXmMh6X69JiYAlCk6mRB9JkaVpgm6hBreSSWR Nw6A3i436J/E6K6qGdvOWifR4HazsiCdIuKHaTW6YUgfbcZixV3XPO+5Mpn1oWSX48CK JEfzzwPywgniB8H6iHcXhqa2b/c9ymutKOspxYkpHzjdB4OGEV6aHlENcJw4vcrbKvYs YO0MraI15x9eVa2YnMLihpTofBfqHSpuXOuN9Zj5lr9TjxvoTMpvMHRJg+1hLTONiH+K dsA+aQxrTv2RaxUtd5P1HtHEdnce1eT+0YvXEzaCH2OgfIQnuPR2qW9DlYJtMzQdGMiV Gbxw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:openpgp:autocrypt :message-id:date:user-agent:mime-version:in-reply-to :content-language:content-transfer-encoding; bh=GECBsDviO4R03B/RCsfVCSEdE0MlOr5oah5nwGqAhaM=; b=THCMtgEjNouYlG//WP5JdvtB20LhvvJbHEYraVO5WRT3f+PQ25P7VEyvZnRHlbZKtx G4H1NalNwvWeG/P2RXsZNKZ2sussMVqQvb4PgU5WO8Pn+U6LnBA8w6TcAm5qAPU2dK0z Pp5qHW4ntcw4/W2tcxbUiLKxHJqngIzM4wb+5Zcv27OqqDE+4FMqrUJbPUtjQuQTdkrf J3FTayTSrhFlFc61oVTPaq1IG9xjjFvBTmRkc8uJgsXKawtXbtam7x2Tj5R27oLr6OWZ dnCLr2/FQOzT3HbI9qqHDmHYUaqcivqMOJUTPWyB/emNIJnff+FlichVrp8JYFMGdX0L E12Q== X-Gm-Message-State: APjAAAWd7Gihjy+5kBxyBto5hWtF9iOk4GqwwNhpdhBAS825Z9Uz1jq+ pEu9yOjVQ22bJwlSq/qmj3CIolp+ X-Google-Smtp-Source: APXvYqzgUDjDcxF5G7aeh4nwNizcRypmCkv4HZkuJvYFRLdhjtjMagJzTD7c5awvom7BV6ilcZrPkw== X-Received: by 2002:a63:504b:: with SMTP id q11mr483359pgl.188.1569432676432; Wed, 25 Sep 2019 10:31:16 -0700 (PDT) Received: from [10.67.50.53] ([192.19.223.252]) by smtp.googlemail.com with ESMTPSA id r30sm5012627pfl.42.2019.09.25.10.31.13 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 25 Sep 2019 10:31:15 -0700 (PDT) Subject: Re: [PATCH v3 0/2] net: stmmac: Enhanced addressing mode for DWMAC 4.10 To: Jose Abreu , David Miller Cc: "thierry.reding@gmail.com" , "peppe.cavallaro@st.com" , "alexandre.torgue@st.com" , "jonathanh@nvidia.com" , "bbiswas@nvidia.com" , "netdev@vger.kernel.org" , "linux-tegra@vger.kernel.org" References: <20190920170036.22610-1-thierry.reding@gmail.com> <20190924.214508.1949579574079200671.davem@davemloft.net> <20190925.133353.1445361137776125638.davem@davemloft.net> From: Florian Fainelli Openpgp: preference=signencrypt Autocrypt: addr=f.fainelli@gmail.com; prefer-encrypt=mutual; keydata= mQGiBEjPuBIRBACW9MxSJU9fvEOCTnRNqG/13rAGsj+vJqontvoDSNxRgmafP8d3nesnqPyR xGlkaOSDuu09rxuW+69Y2f1TzjFuGpBk4ysWOR85O2Nx8AJ6fYGCoeTbovrNlGT1M9obSFGQ X3IzRnWoqlfudjTO5TKoqkbOgpYqIo5n1QbEjCCwCwCg3DOH/4ug2AUUlcIT9/l3pGvoRJ0E AICDzi3l7pmC5IWn2n1mvP5247urtHFs/uusE827DDj3K8Upn2vYiOFMBhGsxAk6YKV6IP0d ZdWX6fqkJJlu9cSDvWtO1hXeHIfQIE/xcqvlRH783KrihLcsmnBqOiS6rJDO2x1eAgC8meAX SAgsrBhcgGl2Rl5gh/jkeA5ykwbxA/9u1eEuL70Qzt5APJmqVXR+kWvrqdBVPoUNy/tQ8mYc nzJJ63ng3tHhnwHXZOu8hL4nqwlYHRa9eeglXYhBqja4ZvIvCEqSmEukfivk+DlIgVoOAJbh qIWgvr3SIEuR6ayY3f5j0f2ejUMYlYYnKdiHXFlF9uXm1ELrb0YX4GMHz7QnRmxvcmlhbiBG YWluZWxsaSA8Zi5mYWluZWxsaUBnbWFpbC5jb20+iGYEExECACYCGyMGCwkIBwMCBBUCCAME FgIDAQIeAQIXgAUCVF/S8QUJHlwd3wAKCRBhV5kVtWN2DvCVAJ4u4/bPF4P3jxb4qEY8I2gS 6hG0gACffNWlqJ2T4wSSn+3o7CCZNd7SLSC5BA0ESM+4EhAQAL/o09boR9D3Vk1Tt7+gpYr3 WQ6hgYVON905q2ndEoA2J0dQxJNRw3snabHDDzQBAcqOvdi7YidfBVdKi0wxHhSuRBfuOppu pdXkb7zxuPQuSveCLqqZWRQ+Cc2QgF7SBqgznbe6Ngout5qXY5Dcagk9LqFNGhJQzUGHAsIs hap1f0B1PoUyUNeEInV98D8Xd/edM3mhO9nRpUXRK9Bvt4iEZUXGuVtZLT52nK6Wv2EZ1TiT OiqZlf1P+vxYLBx9eKmabPdm3yjalhY8yr1S1vL0gSA/C6W1o/TowdieF1rWN/MYHlkpyj9c Rpc281gAO0AP3V1G00YzBEdYyi0gaJbCEQnq8Vz1vDXFxHzyhgGz7umBsVKmYwZgA8DrrB0M oaP35wuGR3RJcaG30AnJpEDkBYHznI2apxdcuTPOHZyEilIRrBGzDwGtAhldzlBoBwE3Z3MY 31TOpACu1ZpNOMysZ6xiE35pWkwc0KYm4hJA5GFfmWSN6DniimW3pmdDIiw4Ifcx8b3mFrRO BbDIW13E51j9RjbO/nAaK9ndZ5LRO1B/8Fwat7bLzmsCiEXOJY7NNpIEpkoNoEUfCcZwmLrU +eOTPzaF6drw6ayewEi5yzPg3TAT6FV3oBsNg3xlwU0gPK3v6gYPX5w9+ovPZ1/qqNfOrbsE FRuiSVsZQ5s3AAMFD/9XjlnnVDh9GX/r/6hjmr4U9tEsM+VQXaVXqZuHKaSmojOLUCP/YVQo 7IiYaNssCS4FCPe4yrL4FJJfJAsbeyDykMN7wAnBcOkbZ9BPJPNCbqU6dowLOiy8AuTYQ48m vIyQ4Ijnb6GTrtxIUDQeOBNuQC/gyyx3nbL/lVlHbxr4tb6YkhkO6shjXhQh7nQb33FjGO4P WU11Nr9i/qoV8QCo12MQEo244RRA6VMud06y/E449rWZFSTwGqb0FS0seTcYNvxt8PB2izX+ HZA8SL54j479ubxhfuoTu5nXdtFYFj5Lj5x34LKPx7MpgAmj0H7SDhpFWF2FzcC1bjiW9mjW HaKaX23Awt97AqQZXegbfkJwX2Y53ufq8Np3e1542lh3/mpiGSilCsaTahEGrHK+lIusl6mz Joil+u3k01ofvJMK0ZdzGUZ/aPMZ16LofjFA+MNxWrZFrkYmiGdv+LG45zSlZyIvzSiG2lKy kuVag+IijCIom78P9jRtB1q1Q5lwZp2TLAJlz92DmFwBg1hyFzwDADjZ2nrDxKUiybXIgZp9 aU2d++ptEGCVJOfEW4qpWCCLPbOT7XBr+g/4H3qWbs3j/cDDq7LuVYIe+wchy/iXEJaQVeTC y5arMQorqTFWlEOgRA8OP47L9knl9i4xuR0euV6DChDrguup2aJVU4hPBBgRAgAPAhsMBQJU X9LxBQkeXB3fAAoJEGFXmRW1Y3YOj4UAn3nrFLPZekMeqX5aD/aq/dsbXSfyAKC45Go0YyxV HGuUuzv+GKZ6nsysJ7kCDQRXG8fwARAA6q/pqBi5PjHcOAUgk2/2LR5LjjesK50bCaD4JuNc YDhFR7Vs108diBtsho3w8WRd9viOqDrhLJTroVckkk74OY8r+3t1E0Dd4wHWHQZsAeUvOwDM PQMqTUBFuMi6ydzTZpFA2wBR9x6ofl8Ax+zaGBcFrRlQnhsuXLnM1uuvS39+pmzIjasZBP2H UPk5ifigXcpelKmj6iskP3c8QN6x6GjUSmYx+xUfs/GNVSU1XOZn61wgPDbgINJd/THGdqiO iJxCLuTMqlSsmh1+E1dSdfYkCb93R/0ZHvMKWlAx7MnaFgBfsG8FqNtZu3PCLfizyVYYjXbV WO1A23riZKqwrSJAATo5iTS65BuYxrFsFNPrf7TitM8E76BEBZk0OZBvZxMuOs6Z1qI8YKVK UrHVGFq3NbuPWCdRul9SX3VfOunr9Gv0GABnJ0ET+K7nspax0xqq7zgnM71QEaiaH17IFYGS sG34V7Wo3vyQzsk7qLf9Ajno0DhJ+VX43g8+AjxOMNVrGCt9RNXSBVpyv2AMTlWCdJ5KI6V4 KEzWM4HJm7QlNKE6RPoBxJVbSQLPd9St3h7mxLcne4l7NK9eNgNnneT7QZL8fL//s9K8Ns1W t60uQNYvbhKDG7+/yLcmJgjF74XkGvxCmTA1rW2bsUriM533nG9gAOUFQjURkwI8jvMAEQEA AYkCaAQYEQIACQUCVxvH8AIbAgIpCRBhV5kVtWN2DsFdIAQZAQIABgUCVxvH8AAKCRCH0Jac RAcHBIkHD/9nmfog7X2ZXMzL9ktT++7x+W/QBrSTCTmq8PK+69+INN1ZDOrY8uz6htfTLV9+ e2W6G8/7zIvODuHk7r+yQ585XbplgP0V5Xc8iBHdBgXbqnY5zBrcH+Q/oQ2STalEvaGHqNoD UGyLQ/fiKoLZTPMur57Fy1c9rTuKiSdMgnT0FPfWVDfpR2Ds0gpqWePlRuRGOoCln5GnREA/ 2MW2rWf+CO9kbIR+66j8b4RUJqIK3dWn9xbENh/aqxfonGTCZQ2zC4sLd25DQA4w1itPo+f5 V/SQxuhnlQkTOCdJ7b/mby/pNRz1lsLkjnXueLILj7gNjwTabZXYtL16z24qkDTI1x3g98R/ xunb3/fQwR8FY5/zRvXJq5us/nLvIvOmVwZFkwXc+AF+LSIajqQz9XbXeIP/BDjlBNXRZNdo dVuSU51ENcMcilPr2EUnqEAqeczsCGpnvRCLfVQeSZr2L9N4svNhhfPOEscYhhpHTh0VPyxI pPBNKq+byuYPMyk3nj814NKhImK0O4gTyCK9b+gZAVvQcYAXvSouCnTZeJRrNHJFTgTgu6E0 caxTGgc5zzQHeX67eMzrGomG3ZnIxmd1sAbgvJUDaD2GrYlulfwGWwWyTNbWRvMighVdPkSF 6XFgQaosWxkV0OELLy2N485YrTr2Uq64VKyxpncLh50e2RnyAJ9Za0Dx0yyp44iD1OvHtkEI M5kY0ACeNhCZJvZ5g4C2Lc9fcTHu8jxmEkI= Message-ID: <9f0e2386-c4b1-52b0-6881-e72093eb1b05@gmail.com> Date: Wed, 25 Sep 2019 10:31:13 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 9/25/19 4:46 AM, Jose Abreu wrote: > From: Jose Abreu > Date: Sep/25/2019, 12:41:04 (UTC+00:00) > >> 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. > > Oops, sorry. Indeed it's done in refill operation in function > dwmac4_set_addr() for rx/tx which is fast path so you do have a point > that I was not seeing. Thanks for bringing this up! > > Now, the point would be: > a) Is it faster to have an condition check in dwmac4_set_addr(), or > b) Always write to descs the upper 32 bits. Which always exists in the > IP and is a standard write to memory. The way I would approach it (as done in bcmgenet.c) is that if the platform both has CONFIG_PHYS_ADDR_T_64BIT=y and supports > 32-bits addresses, then you write the upper 32-bits otherwise, you do not. Given you indicate that the registers are safe to write regardless, then maybe just the check on CONFIG_PHYS_ADDR_T_64BIT is enough for your case. The rationale in my case is that register writes to on-chip descriptors are fairly expensive (~200ns per operation) and get in the hot-path. The CONFIG_PHYS_ADDR_T_64BIT check addresses both native 64-bit platforms (e.g.: ARM64) and those that do support LPAE (ARM LPAE for instance). -- Florian