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[209.132.180.67]) by mx.google.com with ESMTP id 26si5947167edz.340.2019.11.01.01.40.57; Fri, 01 Nov 2019 01:40:57 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; dkim=pass header.i=@ti.com header.s=ti-com-17Q1 header.b="P/qQ6BXr"; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=QUARANTINE sp=NONE dis=NONE) header.from=ti.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727506AbfKAIkw (ORCPT + 26 others); Fri, 1 Nov 2019 04:40:52 -0400 Received: from fllv0015.ext.ti.com ([198.47.19.141]:43536 "EHLO fllv0015.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727434AbfKAIkv (ORCPT ); Fri, 1 Nov 2019 04:40:51 -0400 Received: from fllv0034.itg.ti.com ([10.64.40.246]) by fllv0015.ext.ti.com (8.15.2/8.15.2) with ESMTP id xA18eguC021432; Fri, 1 Nov 2019 03:40:42 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ti.com; s=ti-com-17Q1; t=1572597642; bh=uSViP+QvJDzIv6c8dhx5jMKNUxJQ+VwAKiFTRE1e4co=; h=From:To:CC:Subject:Date:In-Reply-To:References; b=P/qQ6BXrSgsv0ph2C4k4N5BCBZ31a3qn/yiywU4XDiRnRJdG1t15QCOI+Ujf+wkJB FEr4CiyPOjPne7mV0/M473Gw7oXktzbqiWqw2PACcllWGtJS5ydJ14Opl3euuzYFV6 kKc9DKhA14jsaKrceFPUjjB8+XWIcJVWyCii7c68= Received: from DLEE113.ent.ti.com (dlee113.ent.ti.com [157.170.170.24]) by fllv0034.itg.ti.com (8.15.2/8.15.2) with ESMTPS id xA18egjg046689 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=FAIL); Fri, 1 Nov 2019 03:40:42 -0500 Received: from DLEE107.ent.ti.com (157.170.170.37) by DLEE113.ent.ti.com (157.170.170.24) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.1713.5; Fri, 1 Nov 2019 03:40:28 -0500 Received: from lelv0327.itg.ti.com (10.180.67.183) by DLEE107.ent.ti.com (157.170.170.37) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.1713.5 via Frontend Transport; Fri, 1 Nov 2019 03:40:41 -0500 Received: from feketebors.ti.com (ileax41-snat.itg.ti.com [10.172.224.153]) by lelv0327.itg.ti.com (8.15.2/8.15.2) with ESMTP id xA18eP8c036903; Fri, 1 Nov 2019 03:40:37 -0500 From: Peter Ujfalusi To: , , , CC: , , , , , , , , , Subject: [PATCH v4 03/15] dmaengine: doc: Add sections for per descriptor metadata support Date: Fri, 1 Nov 2019 10:41:23 +0200 Message-ID: <20191101084135.14811-4-peter.ujfalusi@ti.com> X-Mailer: git-send-email 2.23.0 In-Reply-To: <20191101084135.14811-1-peter.ujfalusi@ti.com> References: <20191101084135.14811-1-peter.ujfalusi@ti.com> MIME-Version: 1.0 X-EXCLAIMER-MD-CONFIG: e1e8a2fd-e40a-4ac6-ac9b-f7e9cc9ee180 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Update the provider and client documentation with details about the metadata support. Signed-off-by: Peter Ujfalusi Reviewed-by: Tero Kristo --- Documentation/driver-api/dmaengine/client.rst | 75 +++++++++++++++++++ .../driver-api/dmaengine/provider.rst | 46 ++++++++++++ 2 files changed, 121 insertions(+) -- Peter Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki. Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki diff --git a/Documentation/driver-api/dmaengine/client.rst b/Documentation/driver-api/dmaengine/client.rst index 45953f171500..41309c176df4 100644 --- a/Documentation/driver-api/dmaengine/client.rst +++ b/Documentation/driver-api/dmaengine/client.rst @@ -151,6 +151,81 @@ The details of these operations are: Note that callbacks will always be invoked from the DMA engines tasklet, never from interrupt context. + Optional: per descriptor metadata + --------------------------------- + DMAengine provides two ways for metadata support. + + DESC_METADATA_CLIENT + + The metadata buffer is allocated/provided by the client driver and it is + attached to the descriptor. + + .. code-block:: c + + int dmaengine_desc_attach_metadata(struct dma_async_tx_descriptor *desc, + void *data, size_t len); + + DESC_METADATA_ENGINE + + The metadata buffer is allocated/managed by the DMA driver. The client + driver can ask for the pointer, maximum size and the currently used size of + the metadata and can directly update or read it. + + .. code-block:: c + + void *dmaengine_desc_get_metadata_ptr(struct dma_async_tx_descriptor *desc, + size_t *payload_len, size_t *max_len); + + int dmaengine_desc_set_metadata_len(struct dma_async_tx_descriptor *desc, + size_t payload_len); + + Client drivers can query if a given mode is supported with: + + .. code-block:: c + + bool dmaengine_is_metadata_mode_supported(struct dma_chan *chan, + enum dma_desc_metadata_mode mode); + + Depending on the used mode client drivers must follow different flow. + + DESC_METADATA_CLIENT + + - DMA_MEM_TO_DEV / DEV_MEM_TO_MEM: + 1. prepare the descriptor (dmaengine_prep_*) + construct the metadata in the client's buffer + 2. use dmaengine_desc_attach_metadata() to attach the buffer to the + descriptor + 3. submit the transfer + - DMA_DEV_TO_MEM: + 1. prepare the descriptor (dmaengine_prep_*) + 2. use dmaengine_desc_attach_metadata() to attach the buffer to the + descriptor + 3. submit the transfer + 4. when the transfer is completed, the metadata should be available in the + attached buffer + + DESC_METADATA_ENGINE + + - DMA_MEM_TO_DEV / DEV_MEM_TO_MEM: + 1. prepare the descriptor (dmaengine_prep_*) + 2. use dmaengine_desc_get_metadata_ptr() to get the pointer to the + engine's metadata area + 3. update the metadata at the pointer + 4. use dmaengine_desc_set_metadata_len() to tell the DMA engine the + amount of data the client has placed into the metadata buffer + 5. submit the transfer + - DMA_DEV_TO_MEM: + 1. prepare the descriptor (dmaengine_prep_*) + 2. submit the transfer + 3. on transfer completion, use dmaengine_desc_get_metadata_ptr() to get the + pointer to the engine's metadata area + 4. Read out the metadata from the pointer + + .. note:: + + Mixed use of DESC_METADATA_CLIENT / DESC_METADATA_ENGINE is not allowed, + client drivers must use either of the modes per descriptor. + 4. Submit the transaction Once the descriptor has been prepared and the callback information diff --git a/Documentation/driver-api/dmaengine/provider.rst b/Documentation/driver-api/dmaengine/provider.rst index dfc4486b5743..da557c21c619 100644 --- a/Documentation/driver-api/dmaengine/provider.rst +++ b/Documentation/driver-api/dmaengine/provider.rst @@ -247,6 +247,52 @@ after each transfer. In case of a ring buffer, they may loop (DMA_CYCLIC). Addresses pointing to a device's register (e.g. a FIFO) are typically fixed. +Per descriptor metadata support +------------------------------- +Some data movement architecture (DMA controller and peripherals) uses metadata +associated with a transaction. The DMA controller role is to transfer the +payload and the metadata alongside. +The metadata itself is not used by the DMA engine itself, but it contains +parameters, keys, vectors, etc for peripheral or from the peripheral. + +The DMAengine framework provides a generic ways to facilitate the metadata for +descriptors. Depending on the architecture the DMA driver can implement either +or both of the methods and it is up to the client driver to choose which one +to use. + +- DESC_METADATA_CLIENT + + The metadata buffer is allocated/provided by the client driver and it is + attached (via the dmaengine_desc_attach_metadata() helper to the descriptor. + + From the DMA driver the following is expected for this mode: + - DMA_MEM_TO_DEV / DEV_MEM_TO_MEM + The data from the provided metadata buffer should be prepared for the DMA + controller to be sent alongside of the payload data. Either by copying to a + hardware descriptor, or highly coupled packet. + - DMA_DEV_TO_MEM + On transfer completion the DMA driver must copy the metadata to the client + provided metadata buffer. + +- DESC_METADATA_ENGINE + + The metadata buffer is allocated/managed by the DMA driver. The client driver + can ask for the pointer, maximum size and the currently used size of the + metadata and can directly update or read it. dmaengine_desc_get_metadata_ptr() + and dmaengine_desc_set_metadata_len() is provided as helper functions. + + From the DMA driver the following is expected for this mode: + - get_metadata_ptr + Should return a pointer for the metadata buffer, the maximum size of the + metadata buffer and the currently used / valid (if any) bytes in the buffer. + - set_metadata_len + It is called by the clients after it have placed the metadata to the buffer + to let the DMA driver know the number of valid bytes provided. + + Note: since the client will ask for the metadata pointer in the completion + callback (in DMA_DEV_TO_MEM case) the DMA driver must ensure that the + descriptor is not freed up prior the callback is called. + Device operations -----------------