From: Peter Ujfalusi <peter.ujfalusi@ti.com>
To: <vkoul@kernel.org>, <robh+dt@kernel.org>, <nm@ti.com>,
<ssantosh@kernel.org>
Cc: <dan.j.williams@intel.com>, <dmaengine@vger.kernel.org>,
<linux-arm-kernel@lists.infradead.org>,
<devicetree@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
<grygorii.strashko@ti.com>, <lokeshvutla@ti.com>,
<t-kristo@ti.com>, <tony@atomide.com>, <j-keerthy@ti.com>
Subject: [PATCH v4 03/15] dmaengine: doc: Add sections for per descriptor metadata support
Date: Fri, 1 Nov 2019 10:41:23 +0200 [thread overview]
Message-ID: <20191101084135.14811-4-peter.ujfalusi@ti.com> (raw)
In-Reply-To: <20191101084135.14811-1-peter.ujfalusi@ti.com>
Update the provider and client documentation with details about the
metadata support.
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Reviewed-by: Tero Kristo <t-kristo@ti.com>
---
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 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
-----------------
--
Peter
Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki.
Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki
next prev parent reply other threads:[~2019-11-01 8:40 UTC|newest]
Thread overview: 55+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-01 8:41 [PATCH v4 00/15] dmaengine/soc: Add Texas Instruments UDMA support Peter Ujfalusi
2019-11-01 8:41 ` [PATCH v4 01/15] bindings: soc: ti: add documentation for k3 ringacc Peter Ujfalusi
2019-11-11 4:07 ` Vinod Koul
2019-11-11 7:24 ` Peter Ujfalusi
2019-11-01 8:41 ` [PATCH v4 02/15] soc: ti: k3: add navss ringacc driver Peter Ujfalusi
2019-11-11 4:21 ` Vinod Koul
2019-11-11 7:39 ` Peter Ujfalusi
2019-11-01 8:41 ` Peter Ujfalusi [this message]
2019-11-01 8:41 ` [PATCH v4 04/15] dmaengine: Add metadata_ops for dma_async_tx_descriptor Peter Ujfalusi
2019-11-01 8:41 ` [PATCH v4 05/15] dmaengine: Add support for reporting DMA cached data amount Peter Ujfalusi
2019-11-11 4:39 ` Vinod Koul
2019-11-11 8:00 ` Peter Ujfalusi
2019-11-01 8:41 ` [PATCH v4 06/15] dmaengine: ti: Add cppi5 header for K3 NAVSS/UDMA Peter Ujfalusi
2019-11-05 7:40 ` Tero Kristo
2019-11-01 8:41 ` [PATCH v4 07/15] dmaengine: ti: k3 PSI-L remote endpoint configuration Peter Ujfalusi
2019-11-05 7:49 ` Tero Kristo
2019-11-05 8:13 ` Peter Ujfalusi
2019-11-05 10:00 ` Grygorii Strashko
2019-11-05 10:27 ` Peter Ujfalusi
2019-11-05 11:25 ` Grygorii Strashko
2019-11-11 4:47 ` Vinod Koul
2019-11-11 8:47 ` Peter Ujfalusi
2019-11-01 8:41 ` [PATCH v4 08/15] dt-bindings: dma: ti: Add document for K3 UDMA Peter Ujfalusi
2019-11-05 2:19 ` Rob Herring
2019-11-05 10:08 ` Peter Ujfalusi
2019-11-14 17:53 ` Rob Herring
2019-11-15 9:45 ` Peter Ujfalusi
2019-11-26 8:29 ` Peter Ujfalusi
2019-11-01 8:41 ` [PATCH v4 09/15] dmaengine: ti: New driver for K3 UDMA - split#1: defines, structs, io func Peter Ujfalusi
2019-11-11 5:28 ` Vinod Koul
2019-11-11 8:33 ` Peter Ujfalusi
2019-11-11 9:00 ` Vinod Koul
2019-11-11 9:12 ` Peter Ujfalusi
2019-11-01 8:41 ` [PATCH v4 10/15] dmaengine: ti: New driver for K3 UDMA - split#2: probe/remove, xlate and filter_fn Peter Ujfalusi
2019-11-11 5:33 ` Vinod Koul
2019-11-11 9:16 ` Peter Ujfalusi
2019-11-12 5:34 ` Vinod Koul
2019-11-12 7:22 ` Peter Ujfalusi
2019-11-01 8:41 ` [PATCH v4 11/15] dmaengine: ti: New driver for K3 UDMA - split#3: alloc/free chan_resources Peter Ujfalusi
2019-11-11 6:06 ` Vinod Koul
2019-11-11 9:40 ` Peter Ujfalusi
2019-11-01 8:41 ` [PATCH v4 12/15] dmaengine: ti: New driver for K3 UDMA - split#4: dma_device callbacks 1 Peter Ujfalusi
2019-11-11 6:09 ` Vinod Koul
2019-11-11 10:29 ` Peter Ujfalusi
2019-11-12 5:36 ` Vinod Koul
2019-11-12 7:24 ` Peter Ujfalusi
2019-11-01 8:41 ` [PATCH v4 13/15] dmaengine: ti: New driver for K3 UDMA - split#5: dma_device callbacks 2 Peter Ujfalusi
2019-11-01 8:41 ` [PATCH v4 14/15] dmaengine: ti: New driver for K3 UDMA - split#6: Kconfig and Makefile Peter Ujfalusi
2019-11-11 6:11 ` Vinod Koul
2019-11-11 10:30 ` Peter Ujfalusi
2019-11-01 8:41 ` [PATCH v4 15/15] dmaengine: ti: k3-udma: Add glue layer for non DMAengine users Peter Ujfalusi
2019-11-11 6:12 ` Vinod Koul
2019-11-11 10:31 ` Peter Ujfalusi
2019-11-12 5:37 ` Vinod Koul
2019-11-12 7:25 ` Peter Ujfalusi
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