From patchwork Wed Sep 12 06:45:11 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Peter Ujfalusi X-Patchwork-Id: 10596883 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id D918B14DB for ; Wed, 12 Sep 2018 06:45:16 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id C73B329735 for ; Wed, 12 Sep 2018 06:45:16 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id BBC9C29744; Wed, 12 Sep 2018 06:45:16 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.0 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 2D5BE29735 for ; Wed, 12 Sep 2018 06:45:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727183AbeILLsI (ORCPT ); Wed, 12 Sep 2018 07:48:08 -0400 Received: from fllv0015.ext.ti.com ([198.47.19.141]:42398 "EHLO fllv0015.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725910AbeILLsI (ORCPT ); Wed, 12 Sep 2018 07:48:08 -0400 Received: from dflxv15.itg.ti.com ([128.247.5.124]) by fllv0015.ext.ti.com (8.15.2/8.15.2) with ESMTP id w8C6igwf100608; Wed, 12 Sep 2018 01:44:42 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ti.com; s=ti-com-17Q1; t=1536734682; bh=bmjfWdunF5/sR9728pygj5Cdw0+J8efP7YdhxVhekr4=; h=From:To:CC:Subject:Date:In-Reply-To:References; b=vk9j9kzFazp8gzaVxYWodKMCm//6jY9TP9Ha4fUc4FsH1/4mevF2A/dy0gzsEz8o1 i26UPsFgtP0xM9mXdMJIYBl1z+J5KagP7t0IXU8VnCCJL6Up8I7bfh46IqvdbbPsdx R41CXwtv6oiqY75V1ilEmxzQfTkkZ5OIm2nNkmJE= Received: from DFLE106.ent.ti.com (dfle106.ent.ti.com [10.64.6.27]) by dflxv15.itg.ti.com (8.14.3/8.13.8) with ESMTP id w8C6igH7001193; Wed, 12 Sep 2018 01:44:42 -0500 Received: from DFLE103.ent.ti.com (10.64.6.24) by DFLE106.ent.ti.com (10.64.6.27) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.1466.3; Wed, 12 Sep 2018 01:44:39 -0500 Received: from dflp32.itg.ti.com (10.64.6.15) by DFLE103.ent.ti.com (10.64.6.24) with Microsoft SMTP Server (version=TLS1_0, cipher=TLS_RSA_WITH_AES_256_CBC_SHA) id 15.1.1466.3 via Frontend Transport; Wed, 12 Sep 2018 01:44:40 -0500 Received: from feketebors.ti.com (ileax41-snat.itg.ti.com [10.172.224.153]) by dflp32.itg.ti.com (8.14.3/8.13.8) with ESMTP id w8C6iZBS013004; Wed, 12 Sep 2018 01:44:38 -0500 From: Peter Ujfalusi To: , CC: , , , Subject: [PATCH v3 1/2] dmaengine: doc: Add sections for per descriptor metadata support Date: Wed, 12 Sep 2018 09:45:11 +0300 Message-ID: <20180912064512.27306-2-peter.ujfalusi@ti.com> X-Mailer: git-send-email 2.18.0 In-Reply-To: <20180912064512.27306-1-peter.ujfalusi@ti.com> References: <20180912064512.27306-1-peter.ujfalusi@ti.com> MIME-Version: 1.0 X-EXCLAIMER-MD-CONFIG: e1e8a2fd-e40a-4ac6-ac9b-f7e9cc9ee180 Sender: dmaengine-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: dmaengine@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP Update the provider and client documentation with details about the metadata support. Signed-off-by: Peter Ujfalusi --- Documentation/driver-api/dmaengine/client.rst | 75 +++++++++++++++++++ .../driver-api/dmaengine/provider.rst | 46 ++++++++++++ 2 files changed, 121 insertions(+) diff --git a/Documentation/driver-api/dmaengine/client.rst b/Documentation/driver-api/dmaengine/client.rst index fbbb2831f29f..0276ddae7ea2 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 are + 4. Read out the metadate 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..9e6d87b3c477 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 architecure (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 -----------------