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=-1.0 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS 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 88283C43381 for ; Thu, 14 Feb 2019 19:33:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4CD3E222DA for ; Thu, 14 Feb 2019 19:33:38 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="RwdWRRsd" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2502797AbfBNTdg (ORCPT ); Thu, 14 Feb 2019 14:33:36 -0500 Received: from mail-ed1-f66.google.com ([209.85.208.66]:40172 "EHLO mail-ed1-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2439858AbfBNTdf (ORCPT ); Thu, 14 Feb 2019 14:33:35 -0500 Received: by mail-ed1-f66.google.com with SMTP id 10so5983841eds.7 for ; Thu, 14 Feb 2019 11:33:33 -0800 (PST) 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=jCFYnuT2tWBWOC0g0FjOQ4KTznOK7HE3xm9ISk3pg9M=; b=RwdWRRsdR7qdA+XuHBq041Wc+i70vqecvaU4h7k4sX7ZrJrciHXx7pS+980uYtPswS AzfuD3dj5NBzv+HrW1R4PLzs8u4LCioRusfRjeNdix6BjBvwnXG1sAMopwH2g9fSov/F ll1wqE5PXCQIQTRxuQcBBvRupmDk+nBfrkCcRAOZYlJeDDFUY3wiMiVa0NdYHjSR3aOE mJSHoceQGv+2AbaOYwyJmhr/YcR6utiBXZYRDVFb4R72V2BS9mtiOMvl3xPde+FgATuc eMUjc2mnwwpx9LgaPKFLV0cf745eOmwsJAOzfGKA1ebAS2dZoqIhapK+0lWDOSj6mHgT ibtg== 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=jCFYnuT2tWBWOC0g0FjOQ4KTznOK7HE3xm9ISk3pg9M=; b=BMmbi+xHAz1jcwOzRAf16LiYAsQ1h4+/7nqcCSwWpAzES690YSmBIW/D2zZOkeqf2B hzFBUiMqTzZHVnMVVBo8t8kxiHAunZLP5HhV22OCTHB9Ttw8v772bGo7VoEmHnhNrYbv CU2fCq2HWre5xzCSLRrLMQiwt8z+tE8T5VBPJX89vAoeqSVw2zJXvwkuwSA6pYJwE9DY rAvIaOzN3EMWf10mOb4oJstgjid6cSrSDirm4QxMylxk5JoZR+m/FA1HSaJm26qvCGyu eyckHQ611xgVNKLUzCZj+Sn/x3oJE/Yysj2heBErZv2grhDnTTA674VrJ5jeOJm1Dahj g9kA== X-Gm-Message-State: AHQUAubQD2CIGM2Bv/wGerjJ6uOIErOtLn/ZG5uP19Su9wIHZYIuYhpK 3eRu5P/YRXSe8M7dIXJ/AsMSGd9n X-Google-Smtp-Source: AHgI3IZ0GTSVFKYa5MzNBE/+WC/fr8AbxtDrkaw2KcSO3i5G5NmPWuRE7MRuyAaLzcIwoxwJ4ltgfQ== X-Received: by 2002:a17:906:6b0f:: with SMTP id q15mr3954525ejr.139.1550172812409; Thu, 14 Feb 2019 11:33:32 -0800 (PST) Received: from [10.67.48.220] ([192.19.223.250]) by smtp.googlemail.com with ESMTPSA id o20sm280568eja.19.2019.02.14.11.33.30 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 14 Feb 2019 11:33:31 -0800 (PST) Subject: Re: [PATCH v1 net-next 2/4] net: dsa: microchip: add MIB counter reading support To: Tristram.Ha@microchip.com Cc: sergio.paracuellos@gmail.com, pavel@ucw.cz, UNGLinuxDriver@microchip.com, netdev@vger.kernel.org, andrew@lunn.ch References: <1549598829-25970-1-git-send-email-Tristram.Ha@microchip.com> <1549598829-25970-3-git-send-email-Tristram.Ha@microchip.com> <20190209172249.GG30856@lunn.ch> 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: <8ad1ec10-0f3f-9c66-a799-23df5a7842c0@gmail.com> Date: Thu, 14 Feb 2019 11:33:17 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.4.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 2/14/19 11:26 AM, Tristram.Ha@microchip.com wrote: >>>>> + /* read only dropped counters when link is not up */ >>>>> + if (p->link_just_down) >>>>> + p->link_just_down = 0; >>>>> + else if (!p->phydev.link) >>>>> + mib->cnt_ptr = dev->reg_mib_cnt; >>>> >>>> This link_just_down stuff is not clear at all. Why can the drop >>>> counters not be read when the link is up? >>> >>> All of the MIB counters, except some that may be marked by driver, do >>> not get updated when the link is down, so it is a waste of time to read >>> them. >> >> Can you use netif_running() to determine that condition? Maintaining your >> own set of variables when the PHY state machine should already determine >> the link state sounds redundant if not error prone. >> > > The driver can store the PHY device pointer passed to it when the port is enabled. But I am a little worried that pointer can be changed or completely gone as it is out of control of the driver. The per-port network device is accessible from dp->slave so you can do netif_running(dp->slave) from your driver, what are you talking about here? > >>> My intention is the driver eventually reads the MIB counters at least >>> every second or faster so that the ethtool API called to show MIB >>> counters gets them from memory rather than starting a read operation. >>> For now that API is called from user space with the ethtool utility, so >>> it may not be called too often and too fast. But theoretically that >>> API can be called from a program continually. >>> >>> For simple switches that do not need to do anything special the MIB >>> read operation does not cause any issue except CPU load, for more >>> complicate switches that need to do some background operations too many >>> read operation can affect some critical functions. >> >> Some switches have a MIB autocast feature taking a snapshot which AFAIR is >> internally implemented as a fast read register with no contention on other >> registers internally, do you have something similar? > > There is no such function in the switch. Every MIB counter read has to go through a single SPI transfer using indirect access. There are no table-like stored values that a single SPI transfer can retrieve all. > > For i2C the access is even slower, but then I do not expect this access mechanism is used when the switch can do more complex things. > Is that something you are considering to change for future designs? -- Florian