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 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 2BA3AC79F82 for ; Tue, 8 Sep 2026 18:59:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=q4dtfQq0LoWw/3ydG1RDjF69SLaKZZaFrrKNUkkKRCQ=; b=zSJN8V/xAWCNkZeanAtMJ0pUX9 VTcsVDAsZlDSBDQFI6ewIb6FgoCbmC40A7xViFFHEa34bdX8kBMoI+cvAfaxTeiWVrx5875XE1Giv M3dsxnmtf0jjJdcl2LY1jwO08JIQGDYmk7/yzeAoUlnr5hPgRDsaW6oo22Ep/Dpl8+SOI+LjTUz79 oHtSZLe7n9aAuwvkR8LiS+FxuSxTtIPj7sRLpdIUlQfcRSKbTJiLuiNgTHWaQ37bDNailcvfW96Rk yfoA0QTr1Gt2sTCOoFIgEOFcXm4hev8fOksuhCWiLe3gj8iQbokGgAfa9gi5IvzopnxQQwPgN9diS dqYgnFEg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1x412i-0000000A19j-0rTc; Tue, 08 Sep 2026 18:59:40 +0000 Received: from mgamail.intel.com ([198.175.65.12]) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1x412g-0000000A19E-05Q3 for linux-arm-kernel@lists.infradead.org; Tue, 08 Sep 2026 18:59:39 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1788893978; x=1820429978; h=date:from:to:cc:subject:message-id:references: mime-version:in-reply-to; bh=fWURKfC0YnKtnpIW+sCXZWGoSCh2jCIDL2blX3O/UH0=; b=hpvlEDoEVYJJFE5KPZ1SEHluwSwPltL9m+i6562+kiBlrV2md/+Zhh1e RyPPYtSWs1GDPXdJEV/sxPlCZi3B7VjVyS0wkg3v6ybdGbV/NN+kcB04D QWQV0g7agiPxH2mAdrrBATfqCxxs4VONwWdeOsdRBiTVJ+szptNRbNPK3 QJFUlQc/PXUUFevuHSk6N5IIE4uR8kdeTFVKtqUZLCz+iL+pDP/bTi6MO g4I8O/VqNRGgfkQDq0GxeXOV4ws6BH/lR5VOPKKQ/bQdovZfusr+8wWdU OvzYWDGymduvVP31Z6fXPs0Wd1pHpgpHZOHtSaZsMxevMPpdG+5iNxhy3 A==; X-CSE-ConnectionGUID: bMOD4dFxT6+umQUhOLTAiA== X-CSE-MsgGUID: 6EyXbcvwS6ONCywkWs/kng== X-IronPort-AV: E=McAfee;i="6800,10657,11900"; a="100828043" X-IronPort-AV: E=Sophos;i="6.25,269,1779174000"; d="scan'208";a="100828043" Received: from fmviesa006.fm.intel.com ([10.60.135.146]) by orvoesa104.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 08 Sep 2026 11:59:36 -0700 X-CSE-ConnectionGUID: SAxxF9giQsaP/2WeIAZ85A== X-CSE-MsgGUID: cktt8h4WT8SZl+P+UCCZbw== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.25,269,1779174000"; d="scan'208";a="266773711" Received: from yilunxu-optiplex-7050.sh.intel.com (HELO localhost) ([10.239.47.46]) by fmviesa006.fm.intel.com with ESMTP; 08 Sep 2026 11:59:33 -0700 Date: Wed, 9 Sep 2026 02:59:32 +0800 From: Xu Yilun To: Heiko Schocher Cc: linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-fpga@vger.kernel.org, Bartosz Golaszewski , Linus Walleij , Michal Simek , Moritz Fischer , Tom Rix , Xu Yilun , linux-gpio@vger.kernel.org Subject: Re: [PATCH v4] driver: fpga: xilinx-selectmap: add csi and rdwr support Message-ID: References: <20260810062105.299808-1-hs@nabladev.com> <6a489d2b-b5d1-0455-793f-f4100fd3b3d1@nabladev.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <6a489d2b-b5d1-0455-793f-f4100fd3b3d1@nabladev.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260908_115938_128058_2FC48149 X-CRM114-Status: GOOD ( 21.62 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org > I would change v5 commit message to: > """ > The driver requests the optional CSI_B and RDWR_B GPIOs with > GPIOD_OUT_HIGH and never touches them again. That flag carries a > logical value, so both signals end up asserted on every board, > whatever polarity the device tree states. Yeah, that's clear now. > > Keeping them asserted works as long as a single FPGA owns the > SelectMAP port. That FPGA is the only device on the bus, so it may > stay selected, and the driver never reads from it, so the port may > stay in write mode. I think keeping them asserted is a bad idea even for single FPGA, isn't it? > > It stops working as soon as two FPGAs share one SelectMAP data bus, > which is the case CSI_B exists for. Both devices are selected all > the time, so every byte written for one of them is clocked into the > other as well, and neither can be configured on its own. > > CSI_B (Chip Select) selects the target FPGA. Assert it before the > configuration data is transferred and deassert it afterwards, so that > only the intended device sees the bus cycles. What if we re-program the 2 FPGAs at the same time? Is there still chance the 2 CS lines are all asserted? Can they be correctly re-programmed in this case? I mean I think this patch does fix the problem of "always assertion", which is good to me. But the changelog seems stop me, it talks all about 2 FPGAs sharing the same bus, which seems more complex than just manipulating the CS. Thanks, Yilun > > RDWR_B (Read/Write) selects the transfer direction on the SelectMAP > interface. Assert it for the write cycles that carry the bitstream and > deassert it afterwards. UG570 wants RDWR_B settled before CSI_B is > asserted, a change while the device is selected aborts the > configuration on the next CCLK. > > Both are requested with GPIOD_OUT_LOW now, the logical 0 that leaves > them deasserted, and their descriptors are kept in the driver private > data. > > A board with one FPGA keeps working. SelectMAP allows the bitstream to > be loaded non-continuously, with CSI_B deasserted between the data > transfers, and a deselected device ignores the bus. > """