From: Tero Kristo <t-kristo@ti.com>
To: Peter Ujfalusi <peter.ujfalusi@ti.com>, <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>,
<tony@atomide.com>, <j-keerthy@ti.com>
Subject: Re: [PATCH v3 03/14] dmaengine: doc: Add sections for per descriptor metadata support
Date: Wed, 9 Oct 2019 10:30:15 +0300 [thread overview]
Message-ID: <6b9be9ea-551a-22e1-a86b-9e149656058f@ti.com> (raw)
In-Reply-To: <20191001061704.2399-4-peter.ujfalusi@ti.com>
On 01/10/2019 09:16, Peter Ujfalusi wrote:
> Update the provider and client documentation with details about the
> metadata support.
>
> Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Couple of typos below, but they don't really change the readability of
the document so:
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..d708e46b88a2 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
are = area?
> + 4. Read out the metadate from the pointer
metadate = metadata?
> +
> + .. 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
architecure = architecture?
> +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
> -----------------
>
>
--
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next prev parent reply other threads:[~2019-10-09 7:30 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-01 6:16 [PATCH v3 00/14] dmaengine/soc: Add Texas Instruments UDMA support Peter Ujfalusi
2019-10-01 6:16 ` [PATCH v3 01/14] bindings: soc: ti: add documentation for k3 ringacc Peter Ujfalusi
2019-10-01 6:16 ` [PATCH v3 02/14] soc: ti: k3: add navss ringacc driver Peter Ujfalusi
2019-10-09 7:14 ` Tero Kristo
2019-10-09 13:27 ` Lokesh Vutla
2019-10-25 9:30 ` Peter Ujfalusi
2019-10-29 8:52 ` Lokesh Vutla
2019-10-30 13:10 ` Grygorii Strashko
2019-10-01 6:16 ` [PATCH v3 03/14] dmaengine: doc: Add sections for per descriptor metadata support Peter Ujfalusi
2019-10-09 7:30 ` Tero Kristo [this message]
2019-10-01 6:16 ` [PATCH v3 04/14] dmaengine: Add metadata_ops for dma_async_tx_descriptor Peter Ujfalusi
2019-10-09 7:37 ` Tero Kristo
2019-10-01 6:16 ` [PATCH v3 05/14] dmaengine: Add support for reporting DMA cached data amount Peter Ujfalusi
2019-10-09 9:17 ` Tero Kristo
2019-10-01 6:16 ` [PATCH v3 06/14] dmaengine: ti: Add cppi5 header for UDMA Peter Ujfalusi
2019-10-09 9:13 ` Tero Kristo
2019-10-01 6:16 ` [PATCH v3 07/14] dt-bindings: dma: ti: Add document for K3 UDMA Peter Ujfalusi
2019-10-10 17:52 ` Rob Herring
2019-10-11 7:30 ` Peter Ujfalusi
2019-10-15 17:30 ` Peter Ujfalusi
2019-10-17 14:03 ` Rob Herring
2019-10-22 11:46 ` Peter Ujfalusi
2019-10-01 6:16 ` [PATCH v3 08/14] dmaengine: ti: New driver for K3 UDMA - split#1: defines, structs, io func Peter Ujfalusi
2019-10-09 13:40 ` Tero Kristo
2019-10-01 6:16 ` [PATCH v3 09/14] dmaengine: ti: New driver for K3 UDMA - split#2: probe/remove, xlate and filter_fn Peter Ujfalusi
2019-10-03 8:35 ` Peter Ujfalusi
2019-10-01 6:17 ` [PATCH v3 10/14] dmaengine: ti: New driver for K3 UDMA - split#3: alloc/free chan_resources Peter Ujfalusi
2019-10-01 6:17 ` [PATCH v3 11/14] dmaengine: ti: New driver for K3 UDMA - split#4: dma_device callbacks 1 Peter Ujfalusi
2019-10-01 6:17 ` [PATCH v3 12/14] dmaengine: ti: New driver for K3 UDMA - split#5: dma_device callbacks 2 Peter Ujfalusi
2019-10-01 6:17 ` [PATCH v3 13/14] dmaengine: ti: New driver for K3 UDMA - split#6: Kconfig and Makefile Peter Ujfalusi
2019-10-01 6:17 ` [PATCH v3 14/14] dmaengine: ti: k3-udma: Add glue layer for non DMAengine users Peter Ujfalusi
2019-10-04 16:35 ` [PATCH v3 00/14] dmaengine/soc: Add Texas Instruments UDMA support santosh.shilimkar
2019-10-08 10:09 ` Peter Ujfalusi
2019-10-09 16:02 ` santosh.shilimkar
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