From patchwork Wed Dec 1 15:40:23 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Francisco Iglesias X-Patchwork-Id: 12650281 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 lists.gnu.org (lists.gnu.org [209.51.188.17]) (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 0B1A8C433EF for ; Wed, 1 Dec 2021 15:53:24 +0000 (UTC) Received: from localhost ([::1]:58916 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1msRvA-00038R-3L for qemu-devel@archiver.kernel.org; Wed, 01 Dec 2021 10:53:24 -0500 Received: from eggs.gnu.org ([209.51.188.92]:48938) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1msRjG-0004DL-NL for qemu-devel@nongnu.org; Wed, 01 Dec 2021 10:41:06 -0500 Received: from mail-dm6nam12on2042.outbound.protection.outlook.com ([40.107.243.42]:60129 helo=NAM12-DM6-obe.outbound.protection.outlook.com) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1msRjC-0000Eg-6s for qemu-devel@nongnu.org; Wed, 01 Dec 2021 10:41:05 -0500 ARC-Seal: i=1; a=rsa-sha256; s=arcselector9901; d=microsoft.com; cv=none; b=dOePCTBIBtA5GA2ncKqJaPLFnZrJTQ69IGp23eyfdB40d4YUGx9zTpu6Dpe81zj8DzB6Qe3BPFGVeKZf6Nn6dlfdSleOEVACtmY4wMzjBSiQNgNlt67jS3wLdHlo5eHTeGwPChZ02RvmqpySWNby6MKuTR59LIDfYIGZjL15TeoI4QDKJpF3Jutmm+yNQ/9pQzF4NbkjsaVJn5rkI08uJFpWd3l9Nd+n+viCqjCAGBnIKI2T7x9NCOiJAS5YBHqUznivBn6Tn1G2E2aIHKrp5UdX5mny+Dywr6ZnkEM/4dkG7+BfUeIyXYFixMbFx1R+ImXNCgRguhq2InzHfcSmrQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector9901; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-AntiSpam-MessageData-ChunkCount:X-MS-Exchange-AntiSpam-MessageData-0:X-MS-Exchange-AntiSpam-MessageData-1; bh=33Ch6Tw7WVzTPw0j1ybbPPRpflZ378Qn7DyX95V3gF8=; b=atY4WB7XZm3ExuBr76HZqg6JON7WzeAsxqNhvw51oMyQyuF6GYW3EX9FLh/tFtaIOFLFs3KmMu5gNQiqUxZT+fJPNxfohvtH0eepdocv6Fv56BR20IQDoWX4sY4K5Pc5XSge8JB4iBCD1lUkNRMiLtMEv/YrzS3V8QKseawIQ1b9F+83yTHdoZh/RMv+1fn2BIMh9InKhRADrf/gE9Q58IjUTy4llpp+5DHM6OTGGFuquE/HtvpQLHhXT0TuxOsXVV5DEKJ344n3SCXTjh5y5BKN+LYRfCvs88OHeSewh/YxiXnn/hhpWh7PrZcYRNNkWTtmFP1ArtzDi6/PqoRViA== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass (sender ip is 149.199.62.198) smtp.rcpttodomain=nongnu.org smtp.mailfrom=xilinx.com; dmarc=pass (p=none sp=none pct=100) action=none header.from=xilinx.com; dkim=none (message not signed); arc=none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=xilinx.onmicrosoft.com; s=selector2-xilinx-onmicrosoft-com; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=33Ch6Tw7WVzTPw0j1ybbPPRpflZ378Qn7DyX95V3gF8=; b=Nigr6oeRXcvGzjp9vhzzksYLTMaOWWxngnHIeF1pYgN3gjR2Q/VhS+UNAR3YTpQJsI1/QwGS50ZAyLbnYnNhcAh6gtqa74UQ/c6TwsZX+Mvi7TQVm6FRRIW1xQNKL+1ZdynzvmiDbX2lvIzwut31KmAyJvnMOCA+IWruQ5uU3MA= Received: from DM5PR20CA0024.namprd20.prod.outlook.com (2603:10b6:3:93::34) by BL0PR02MB6532.namprd02.prod.outlook.com (2603:10b6:208:1c9::21) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4755.14; Wed, 1 Dec 2021 15:40:59 +0000 Received: from DM3NAM02FT024.eop-nam02.prod.protection.outlook.com (2603:10b6:3:93:cafe::92) by DM5PR20CA0024.outlook.office365.com (2603:10b6:3:93::34) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4734.24 via Frontend Transport; Wed, 1 Dec 2021 15:40:59 +0000 X-MS-Exchange-Authentication-Results: spf=pass (sender IP is 149.199.62.198) smtp.mailfrom=xilinx.com; dkim=none (message not signed) header.d=none;dmarc=pass action=none header.from=xilinx.com; Received-SPF: Pass (protection.outlook.com: domain of xilinx.com designates 149.199.62.198 as permitted sender) receiver=protection.outlook.com; client-ip=149.199.62.198; helo=xsj-pvapexch01.xlnx.xilinx.com; Received: from xsj-pvapexch01.xlnx.xilinx.com (149.199.62.198) by DM3NAM02FT024.mail.protection.outlook.com (10.13.5.128) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.20.4755.13 via Frontend Transport; Wed, 1 Dec 2021 15:40:59 +0000 Received: from xsj-pvapexch02.xlnx.xilinx.com (172.19.86.41) by xsj-pvapexch01.xlnx.xilinx.com (172.19.86.40) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2176.14; Wed, 1 Dec 2021 07:40:47 -0800 Received: from smtp.xilinx.com (172.19.127.96) by xsj-pvapexch02.xlnx.xilinx.com (172.19.86.41) with Microsoft SMTP Server id 15.1.2176.14 via Frontend Transport; Wed, 1 Dec 2021 07:40:47 -0800 Received: from [10.23.121.245] (port=59039 helo=debian.xilinx.com) by smtp.xilinx.com with esmtp (Exim 4.90) (envelope-from ) id 1msRix-0002FY-1n; Wed, 01 Dec 2021 07:40:47 -0800 From: Francisco Iglesias To: Subject: [PATCH v4 11/11] docs/devel: Add documentation for the DMA control interface Date: Wed, 1 Dec 2021 15:40:23 +0000 Message-ID: <20211201154023.13931-12-francisco.iglesias@xilinx.com> X-Mailer: git-send-email 2.11.0 In-Reply-To: <20211201154023.13931-1-francisco.iglesias@xilinx.com> References: <20211201154023.13931-1-francisco.iglesias@xilinx.com> MIME-Version: 1.0 X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: b2e4e008-cac8-4c4c-fa4a-08d9b4e0f913 X-MS-TrafficTypeDiagnostic: BL0PR02MB6532: X-Microsoft-Antispam-PRVS: X-Auto-Response-Suppress: DR, RN, NRN, OOF, AutoReply X-MS-Oob-TLC-OOBClassifiers: OLM:6790; X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:149.199.62.198; CTRY:US; LANG:en; SCL:1; SRV:; IPV:NLI; SFV:NSPM; H:xsj-pvapexch01.xlnx.xilinx.com; PTR:unknown-62-198.xilinx.com; CAT:NONE; SFS:(46966006)(36840700001)(9786002)(2906002)(36756003)(186003)(26005)(54906003)(5660300002)(1076003)(356005)(83380400001)(70586007)(70206006)(6666004)(47076005)(316002)(82310400004)(7696005)(4326008)(7636003)(2616005)(36860700001)(44832011)(336012)(508600001)(8676002)(8936002)(426003)(6916009)(102446001); DIR:OUT; SFP:1101; X-OriginatorOrg: xilinx.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 01 Dec 2021 15:40:59.3208 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: b2e4e008-cac8-4c4c-fa4a-08d9b4e0f913 X-MS-Exchange-CrossTenant-Id: 657af505-d5df-48d0-8300-c31994686c5c X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=657af505-d5df-48d0-8300-c31994686c5c; Ip=[149.199.62.198]; Helo=[xsj-pvapexch01.xlnx.xilinx.com] X-MS-Exchange-CrossTenant-AuthSource: DM3NAM02FT024.eop-nam02.prod.protection.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: BL0PR02MB6532 Received-SPF: pass client-ip=40.107.243.42; envelope-from=figlesia@xilinx.com; helo=NAM12-DM6-obe.outbound.protection.outlook.com X-Spam_score_int: -18 X-Spam_score: -1.9 X-Spam_bar: - X-Spam_report: (-1.9 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-0.001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: edgar.iglesias@xilinx.com, peter.maydell@linaro.org, frasse.iglesias@gmail.com, alistair@alistair23.me, alistair23@gmail.com, philmd@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Also, since being the author, list myself as maintainer for the file. Signed-off-by: Francisco Iglesias --- MAINTAINERS | 1 + docs/devel/dma-ctrl-if.rst | 320 +++++++++++++++++++++++++++++++++++++++++++++ docs/devel/index.rst | 1 + 3 files changed, 322 insertions(+) create mode 100644 docs/devel/dma-ctrl-if.rst diff --git a/MAINTAINERS b/MAINTAINERS index e52cc94840..ffefcc841f 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -968,6 +968,7 @@ M: Francisco Iglesias S: Maintained F: hw/ssi/xlnx-versal-ospi.c F: include/hw/ssi/xlnx-versal-ospi.h +F: docs/devel/dma-ctrl-if.rst ARM ACPI Subsystem M: Shannon Zhao diff --git a/docs/devel/dma-ctrl-if.rst b/docs/devel/dma-ctrl-if.rst new file mode 100644 index 0000000000..480e2a7d3a --- /dev/null +++ b/docs/devel/dma-ctrl-if.rst @@ -0,0 +1,320 @@ +DMA control interface +===================== + +About the DMA control interface +------------------------------- + +DMA engines embedded in peripherals can end up being controlled in +different ways on real hardware. One possible way is to allow software +drivers to access the DMA engine's register API and to allow the drivers +to configure and control DMA transfers through the API. A model of a DMA +engine in QEMU that is embedded and (re)used in this manner does not need +to implement the DMA control interface. + +Another option on real hardware is to allow the peripheral embedding the +DMA engine to control the engine through a custom hardware DMA control +interface between the two. Software drivers in this scenario configure and +trigger DMA operations through the controlling peripheral's register API +(for example could writing a specific bit in a register propagate down to +a transfer start signal on the DMA control interface). At the same time +the status, result and interrupts for the transfer might still be intended +to be read and catched through the DMA engine's register API (and +signals). + +:: + + Hardware example + +------------+ + | | + | Peripheral | + | | + +------------+ + /\ + || DMA control IF (custom) + \/ + +------------+ + | Peripheral | + | DMA | + +------------+ + +Figure 1. A peripheral controlling it's embedded DMA engine through a +custom DMA control interface + +Above scenario can be modelled in QEMU by implementing this DMA control +interface in the DMA engine model. This will allow a peripheral embedding +the DMA engine to initiate DMA transfers through the engine using the +interface. At the same time the status, result and interrupts for the +transfer can be read and catched through the DMA engine's register API and +signals. An example implementation and usage of the DMA control interface +can be found in the Xilinx CSU DMA model and Xilinx Versal's OSPI model. + +:: + + Memory address + (register API) + 0xf1010000 +---------+ + | | + | Versal | + | OSPI | + | | + +---------+ + /\ + || DMA control IF + \/ + 0xf1011000 +---------+ + | | + | CSU DMA | + | (src) | + | | + +---------+ + +Figure 2. Xilinx Versal's OSPI controls and initiates transfers on it's +CSU source DMA through a DMA control interface + +DMA control interface files +--------------------------- + +``include/hw/dma/dma-ctrl-if.h`` +``hw/dma/dma-ctrl-if.c`` + +DmaCtrlIfClass +-------------- + +The ``DmaCtrlIfClass`` contains the interface methods that can be +implemented by a DMA engine. + +.. code-block:: c + + typedef struct DmaCtrlIfClass { + InterfaceClass parent; + + /* + * read: Start a read transfer on the DMA implementing the DMA control + * interface + * + * @dma_ctrl: the DMA implementing this interface + * @addr: the address to read + * @len: the amount of bytes to read at 'addr' + * @notify: the structure containg a callback to call and opaque pointer + * to pass the callback when the transfer has been completed + * @start_dma: true for starting the DMA transfer and false for just + * refilling and proceding an already started transfer + */ + void (*read)(DmaCtrlIf *dma, hwaddr addr, uint32_t len, + DmaCtrlIfNotify *notify, bool start_dma); + } DmaCtrlIfClass; + + +DmaCtrlIfNotify +--------------- + +The ``DmaCtrlIfNotify`` contains a callback function that is called when a +transfer has been completed. It also contains an opaque pointer that is +passed in to the function as an argument. + +.. code-block:: c + + typedef struct DmaCtrlIfNotify { + void *opaque; + dmactrlif_notify_fn cb; + } DmaCtrlIfNotify; + +dma_ctrl_if_read_with_notify +---------------------------- + +The ``dma_ctrl_if_read_with_notify`` function is used from a model +embedding the DMA engine for starting DMA read transfers. + +.. code-block:: c + + /* + * Start a read transfer on a DMA implementing the DMA control interface. + * The DMA will notify the caller that 'len' bytes have been read at 'addr' + * through the callback in the DmaCtrlIfNotify structure. For allowing refilling + * an already started transfer the DMA notifies the caller before considering + * the transfer done (e.g. before setting done flags, generating IRQs and + * modifying other relevant internal device state). + * + * @dma_ctrl: the DMA implementing this interface + * @addr: the address to read + * @len: the amount of bytes to read at 'addr' + * @notify: the structure containing a callback to call and opaque pointer + * to pass the callback when the transfer has been completed + * @start_dma: true for starting the DMA transfer and false for just + * refilling and proceding an already started transfer + */ + void dma_ctrl_if_read_with_notify(DmaCtrlIf *dma, hwaddr addr, uint32_t len, + DmaCtrlIfNotify *notify, bool start_dma); + +Example implementation of the DMA control interface +--------------------------------------------------- + +The example code below showing an implementation of the DMA control +interface is taken from the Xilinx CSU DMA model. + +The DMA control interface related code in +``include/hw/dma/xlnx_csu_dma.h`` is found below. The header includes +``include/hw/dma/dma-ctrl-if.h`` and makes it possible to keep track of a +notifier function with a corresponding opaque. The notifier is called when +the transfer has been completed (with the opaque passed in as argument). + +.. code-block:: c + + . + . + . + #include "hw/dma/dma-ctrl-if.h" + . + . + . + typedef struct XlnxCSUDMA { + . + . + . + dmactrlif_notify_fn dmactrlif_notify; + void *dmactrlif_opaque; + . + . + . + } XlnxCSUDMA; + . + . + . + +The DMA control interface related code inside ``hw/dma/xlnx_csu_dma.c`` is +shown below. A DMA control interface read function gets installed in the +class init function through which DMA read transfers can be started. The +DMA control interface notifier is called once a transfer has been +completed (with the opaque passed in as argument) but before any DMA +status has been updated (for allowing refilling the transfer). + +.. code-block:: c + + . + . + . + static uint32_t xlnx_csu_dma_advance(XlnxCSUDMA *s, uint32_t len) + { + . + . + . + /* Notify dma-ctrl-if clients when the transfer has been completed */ + if (size == 0 && s->dmactrlif_notify) { + s->dmactrlif_notify(s->dmactrlif_opaque); + } + + if (size == 0) { + xlnx_csu_dma_done(s); + } + + return size; + } + . + . + . + static void xlnx_csu_dma_dma_ctrl_if_read(DmaCtrlIf *dma, hwaddr addr, + uint32_t len, DmaCtrlIfNotify *notify, + bool start_dma) + { + . + . + . + static void xlnx_csu_dma_class_init(ObjectClass *klass, void *data) + { + DeviceClass *dc = DEVICE_CLASS(klass); + StreamSinkClass *ssc = STREAM_SINK_CLASS(klass); + DmaCtrlIfClass *dcic = DMA_CTRL_IF_CLASS(klass); + . + . + . + dcic->read = xlnx_csu_dma_dma_ctrl_if_read; + } + . + . + . + static const TypeInfo xlnx_csu_dma_info = { + . + . + . + .interfaces = (InterfaceInfo[]) { + { TYPE_STREAM_SINK }, + { TYPE_DMA_CTRL_IF }, + { } + } + }; + +Example DMA control interface read transfer start +------------------------------------------------- + +The DMA read transfer example is taken from the Xilinx Versal's OSPI +model. The DMA read transfer is started by a register write to the OSPI +controller. + +The DMA control interface related code inside +``include/hw/ssi/xlnx-versal-ospi.h`` is shown below. The header includes +``include/hw/dma/dma-ctrl-if.h`` and the state structure contains a +pointer to a DMA engine that has implemented the DMA control interface. + +.. code-block:: c + + . + . + . + #include "hw/dma/dma-ctrl-if.h" + . + . + . + typedef struct XlnxVersalOspi { + . + . + . + DmaCtrlIf *dma_src; + . + . + . + } XlnxVersalOspi; + . + . + . + +The DMA control interface related code inside +``hw/ssi/xlnx-versal-ospi.c`` can be seen below. OSPI DMA read transfers +are performed and executed through the DMA control interface read function +(and with the CSU source DMA). The OSPI controller is also able to refill +the transfer as required through the notifier (which is called when the +transfer has been completed). + +.. code-block:: c + + static void ospi_dma_read(XlnxVersalOspi *s, bool start_dma) + { + . + . + . + DmaCtrlIfNotify notify = { .cb = ospi_notify, + .opaque = (void *)s }; + . + . + . + dma_ctrl_if_read_with_notify(s->dma_src, 0, dma_len, + ¬ify, start_dma); + . + . + . + } + . + . + . + static void xlnx_versal_ospi_init(Object *obj) + { + . + . + . + object_property_add_link(obj, "dma-src", TYPE_DMA_CTRL_IF, + (Object **)&s->dma_src, + object_property_allow_set_link, + OBJ_PROP_LINK_STRONG); + . + . + . + } diff --git a/docs/devel/index.rst b/docs/devel/index.rst index afd937535e..0d424bdf34 100644 --- a/docs/devel/index.rst +++ b/docs/devel/index.rst @@ -37,6 +37,7 @@ modifying QEMU's source code. reset s390-dasd-ipl clocks + dma-ctrl-if qom modules block-coroutine-wrapper