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=-1.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,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 CD578C83003 for ; Thu, 30 Apr 2020 03:12:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A51442073E for ; Thu, 30 Apr 2020 03:12:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1588216334; bh=zFkysDiNlWdgOMOnQZac9a25NNHGxo2POncv2jmusUI=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=rU6tZ3En7xI8WO7b8iWKdPk6JoKS2CGG9byb+dObGnwYQBeFiHmEJ+hnRjG+O/Fp+ ofR1Pn3njrF6i8tgvjylhfsakWD/eRsA1rMyfszrmjJwXfSM3SOy3akeh0+MFOkUfm +QcGz3RBHbiSJ7fjda2PRHjBDoWxL8BoJEAWqjwQ= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726554AbgD3DMO (ORCPT ); Wed, 29 Apr 2020 23:12:14 -0400 Received: from mail-pf1-f173.google.com ([209.85.210.173]:38854 "EHLO mail-pf1-f173.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726357AbgD3DMN (ORCPT ); Wed, 29 Apr 2020 23:12:13 -0400 Received: by mail-pf1-f173.google.com with SMTP id y25so2198824pfn.5; Wed, 29 Apr 2020 20:12:13 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=SMIh/7yA/TcacM5ktTGAgddafFfMiqmeZDeRLLRUZ38=; b=N2mzXORPzsRrJudZJFe1GZB06YTGIF0fSTGsf1/Xur9WAeA23hlhOHaBO1APzaT+Qd HuSM4tyTmxTIsEKN6rAQsyO9alCiwcyM6x1fgox5zj5sj0FP+Kr86MiiTdwYodO0bSMy mRs3+hCPhs8H35EdmtGqltT4d6OVKCR0UEngFZp5U/GF2XiP4Qp+vk1iorA7r0oRkX8r VWvr/bHUiaVLU7BexWuvWlvRSFWIit6SXZOMLMMJQjcdXSImQ2U1bwrgcB9YQi0dfyNI yEXKOEsaT6TCQBO4TtebGpKq7haP3563aKU8QTUV6aMaZ2qeBWaX/XxxU5pPEPPD13Nz A4YA== X-Gm-Message-State: AGi0PubGSjV5rgZM8rlT/4jHyvvYGBWEJszeq6c9r4iFii3zQk9qzExF tdNLhFuKTOWR1QbgUHjDFuk= X-Google-Smtp-Source: APiQypImFjuz5sapmhHaxue1R17ZIKtmudlLldNmU5d8yRcooOIDtm3MCsQy/NjvrO7HHCc89emJww== X-Received: by 2002:a63:ce17:: with SMTP id y23mr1251673pgf.194.1588216332547; Wed, 29 Apr 2020 20:12:12 -0700 (PDT) Received: from localhost ([2601:647:5b00:1161:a4cc:eef9:fbc0:2781]) by smtp.gmail.com with ESMTPSA id x13sm1998429pgh.63.2020.04.29.20.12.11 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 29 Apr 2020 20:12:11 -0700 (PDT) Date: Wed, 29 Apr 2020 20:12:10 -0700 From: Moritz Fischer To: matthew.gerlach@linux.intel.com Cc: Xu Yilun , linux-fpga@vger.kernel.org, linux-kernel@vger.kernel.org, mdf@kernel.org Subject: Re: How to update a piece of flash for FPGA firmware? Message-ID: <20200430031210.GA6168@epycbox.lan> References: <20200428050135.GA27416@yilunxu-OptiPlex-7050> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Matthew, Yilun On Tue, Apr 28, 2020 at 03:06:07PM -0700, matthew.gerlach@linux.intel.com wrote: > Hi Yilun, > > You raise some very interesting questions. Please see > my comments below. > > Matthew > > On Tue, 28 Apr 2020, Xu Yilun wrote: > > > Hi, > > > > I wonder if an updating of FPGA Flash (but cannot reload) could be > > implemented as fpga-mgr? > > > > I have the pcie based FPGA card. The bitstream for FPGA static region is > > stored on flash chip. Board will load the bitstream to FPGA on system > > power cycle. The flash chip could be accessed through "PCIE -> ... -> > > Flash update engine -> Flash". So the update of the FPGA static region is > > basicly updating the flash chip through PCIE and rebooting system. > > I think you mean power cycle when you say "rebooting system" above, but > your point is worth highlighting. During this flash update the > FPGA is actually fully configured and running its application. Typically, > during a fpga-mgr update of the static region or partial reconfiguration > region, the actual contents of the fpga region is "changing" during the > update. Yeah, this sounds more like a flash driver with MTD or maybe NVMEM? That's probably how I'd do it. Depending on your (Q)SPI controller you might already have a driver for that, and you'd just have to instantiate it as a sub-device. > > > > > Should I implement the flash update engine as a fpga-mgr device? On one > > hand it is just a flash write, FPGA functionality is actually not > > changed before reboot. Does fpga-mgr requires bitstream takes function > > immediately after write_complete()? On the other hand, the flash write > > do affects FPGA static region on next boot. Operating on the > > corresponding fpga region makes kernel fully aware of what is being > > done. > > When an fpga-mgr is used in a device tree overlay flow, one gains > the benefit the enumeration of the nodes in the overlay after the > update has completed. I'm not sure how to model 'on next reboot' part. > > > > > Actually the FPGA card do has the capability to reload bitstream at > > runtime. But it will cause the whole PCIE device lost, static region is > > also destroyed. We need to rescan PCI to get it back. So I think > > basically this is the same case as system reboot from FPGA's > > perspective. > > Yes, on those cards that have the ability to power cycle themselves (i.e. > fully reconfigure the FPGA from flash), the PCIe connection to the card > is broken because of a surprise link down PCIe error. As you say a PCI > rescan (i.e. re-enumeration of the entire card) is required. Since > the card has to be re-scanned at the PCI level anyway, there may not be much > benefit to using the fpga-mgr in this flow. Agreed. > > I wonder if these kinds of more disruptive updates are better suited to > something firmware updates rather than fpga updates? Yeah. Cheers, Moritz