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=-2.2 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, 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 9AB84C3A5A1 for ; Wed, 28 Aug 2019 17:14:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 66A7F22DA7 for ; Wed, 28 Aug 2019 17:14:58 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="Vnvh0Xj/" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726614AbfH1ROz (ORCPT ); Wed, 28 Aug 2019 13:14:55 -0400 Received: from mail-pf1-f194.google.com ([209.85.210.194]:40174 "EHLO mail-pf1-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726315AbfH1ROy (ORCPT ); Wed, 28 Aug 2019 13:14:54 -0400 Received: by mail-pf1-f194.google.com with SMTP id w16so206684pfn.7; Wed, 28 Aug 2019 10:14:54 -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=nmX1iH5t+qGsoVau1cVSSS+oy8ShDNckWp+WcaFenT0=; b=Vnvh0Xj/ASJi51jsUph9xt++YDQHzJfdlYwWDRJO+zLKz2zIoxTHkyS2UQ57JpOrIV 6Zbc2fx1HXukVUIVcS6rzxem/CoWtDoNgj8TfywJYln5ht/lFPcgU/wQ0r8izDgVMHek OCQmb6JvRkkOzq+kzaI1+E3u8nXHIiYkdWqgnocE8AncTaK6ATTZpaBb0oLSVjxqCPtc RNnyK66NbV4/Zdo3hDx5CIcP0SkM8Zti5lb6Bgshoi2cuVYSLvno/FdC1+jELybgJP7N c1BcbGIwNOYgty0YliB1dJYfb2cC43CUGwuLrzL+U5tYgrYEjdWZeqwyqD/kDoB/JOLq uPzw== 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=nmX1iH5t+qGsoVau1cVSSS+oy8ShDNckWp+WcaFenT0=; b=AFAsHrFNLR3LuQR7EOBlMHOnqEwZJbn/0tFTNzkjp05bl4AGtBozaI1cFI4B6ttj/Y FKdq6ECPkfPxSAg5YznNcT0uZlpKuYDBuVZar2WdhXb45vtCIKSJmQ0nSK+RoU7QrQ+x QUOQPc3WhktMmNoIS1JGbvHAGDsFO0eZDyxG1AC15csdh++H8zQ58dVKb7K9RvArHd9d KhDMd3xWIhxA/VmknAhSpnZa4O06huFEJo9x03zabMEOoRwY59IEYZPaYuCkU4AF8jD9 sOvEk60wQrscMMYc8Uw5lsEESFAi5gLzOLfs9OaOB82xI+q0Ih38q+e6SgiNRyGwCnnG 0ybA== X-Gm-Message-State: APjAAAWvFBPVYN3sYHbRVx5EPt5lgIdugzDZwNSCozoZErJ7vde15kY0 HIc2/Hh7JMIkioTx5Y75w7g= X-Google-Smtp-Source: APXvYqxY9SmeZYt0VS3ln3DwcM6OqEMQCVzdKMxwJOhUrn8iumNim1xjpg+hYQShXyUJp18QUomh1w== X-Received: by 2002:aa7:9a12:: with SMTP id w18mr6211496pfj.110.1567012493608; Wed, 28 Aug 2019 10:14:53 -0700 (PDT) Received: from [10.67.49.31] ([192.19.223.252]) by smtp.googlemail.com with ESMTPSA id l123sm7132314pfl.9.2019.08.28.10.14.52 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 28 Aug 2019 10:14:52 -0700 (PDT) Subject: Re: [PATCH v1 net-next] net: stmmac: Add support for MDIO interrupts To: "Voon, Weifeng" , Andrew Lunn Cc: "David S. Miller" , Maxime Coquelin , "netdev@vger.kernel.org" , "linux-kernel@vger.kernel.org" , Jose Abreu , Giuseppe Cavallaro , Alexandre Torgue , "Ong, Boon Leong" References: <1566870320-9825-1-git-send-email-weifeng.voon@intel.com> <20190826184719.GF2168@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: Date: Wed, 28 Aug 2019 10:14:50 -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 8/28/19 10:07 AM, Voon, Weifeng wrote: >>>> DW EQoS v5.xx controllers added capability for interrupt generation >>>> when MDIO interface is done (GMII Busy bit is cleared). >>>> This patch adds support for this interrupt on supported HW to avoid >>>> polling on GMII Busy bit. >>>> >>>> stmmac_mdio_read() & stmmac_mdio_write() will sleep until wake_up() >>>> is called by the interrupt handler. >>> >>> Hi Voon >>> >>> I _think_ there are some order of operation issues here. The mdiobus >>> is registered in the probe function. As soon as of_mdiobus_register() >>> is called, the MDIO bus must work. At that point MDIO read/writes can >>> start to happen. >>> >>> As far as i can see, the interrupt handler is only requested in >>> stmmac_open(). So it seems like any MDIO operations after probe, but >>> before open are going to fail? >> >> AFAIR, wait_event_timeout() will continue to busy loop and wait until >> the timeout, but not return an error because the polled condition was >> true, at least that is my recollection from having the same issue with >> the bcmgenet driver before it was moved to connecting to the PHY in the >> ndo_open() function. >> -- >> Florian > > Florian is right as the poll condition is still true after the timeout. > Hence, any mdio operation after probe and before ndo_open will still work. > The only cons here is that attaching the PHY will takes a full length of > timeout time for each mdio_read and mdio_write. > So we should attach the phy only after the interrupt handler is requested? >From a power management/resource utilization perspective, it is better to initialize as close as possible from the time where you are actually going to use the hardware, therefore ndo_open(). This may not be convenient or possible given how widely use stmmac is, and I do not know if parts of the Ethernet MAC require the PHY to supply the clock, in which case, you may have some chicke and egg conditions if the design does not allow for MDIO to work independently from the data plane. Also, I would be worried about introducing bugs. You could do a couple of things: - continue to probe the device with interrupts disabled and add a condition around the call to wait_event_timeout() to do a busy-loop without going to the maximum defined timeout, if the interrupt line is requested, use wait_event_timeout() - request the interrupt during the probe function, but only unmask/enable the MDIO interrupts for the probe to succeed and leave the data path interrupts for a later enabling during ndo_open() -- Florian