Re: [PATCH v2 00/14] dmaengine/soc: Add Texas Instruments UDMA support

[Peter Ujfalusi <peter.ujfalusi@ti.com>]

Rob,

On 30/07/2019 12.34, Peter Ujfalusi wrote:
> Changes since v1
> (https://patchwork.kernel.org/project/linux-dmaengine/list/?series=114105&state=*)
> - Added support for j721e
> - Based on 5.3-rc2
> - dropped ti_sci API patch for RM management as it is already upstream
> - dropped dmadev_get_slave_channel() patch, using __dma_request_channel()
> - Added Rob's Reviewed-by to ringacc DT binding document patch
> - DT bindings changes:
>  - linux,udma-mode is gone, I have a simple lookup table in the driver to flag
>    TR channels.
>  - Support for j721e

I have also made smaller adjustment of some property names within the
psi-l config nodes to make it uniform and more readable.

> - Fix bug in of_node_put() handling in xlate function
> 
> Changes since RFC (https://patchwork.kernel.org/cover/10612465/):
> - Based on linux-next (20190506) which now have the ti_sci interrupt support
> - The series can be applied and the UDMA via DMAengine API will be functional
> - Included in the series: ti_sci Resource management API, cppi5 header and
>   driver for the ring accelerator.
> - The DMAengine core patches have been updated as per the review comments for
>   earlier submittion.
> - The DMAengine driver patch is artificially split up to 6 smaller patches
> 
> The k3-udma driver implements the Data Movement Architecture described in
> AM65x TRM (http://www.ti.com/lit/pdf/spruid7) and
> j721e TRM (http://www.ti.com/lit/pdf/spruil1)
> 
> This DMA architecture is a big departure from 'traditional' architecture where
> we had either EDMA or sDMA as system DMA.
> 
> Packet DMAs were used as dedicated DMAs to service only networking (Kesytone2)
> or USB (am335x) while other peripherals were serviced by EDMA.
> 
> In AM65x/j721e the UDMA (Unified DMA) is used for all data movment within the
> SoC, tasked to service all peripherals (UART, McSPI, McASP, networking, etc). 
> 
> The NAVSS/UDMA is built around CPPI5 (Communications Port Programming Interface)
> and it supports Packet mode (similar to CPPI4.1 in Keystone2 for networking) and
> TR mode (similar to EDMA descriptor).
> The data movement is done within a PSI-L fabric, peripherals (including the
> UDMA-P) are not addressed by their I/O register as with traditional DMAs but
> with their PSI-L thread ID.
> 
> In AM65x/j721e we have two main type of peripherals:
> Legacy: McASP, McSPI, UART, etc.
>  to provide connectivity they are serviced by PDMA (Peripheral DMA)
>  PDMA threads are locked to service a given peripheral, for example PSI-L thread
>  0x4400/0xc400 is to service McASP0 rx/tx.
>  The PDMa configuration can be done via the UDMA Real Time Peer registers.
> Native: Networking, security accelerator
>  these peripherals have native support for PSI-L.
> 
> To be able to use the DMA the following generic steps need to be taken:
> - configure a DMA channel (tchan for TX, rchan for RX)
>  - channel mode: Packet or TR mode
>  - for memcpy a tchan and rchan pair is used.
>  - for packet mode RX we also need to configure a receive flow to configure the
>    packet receiption
> - the source and destination threads must be paired
> - at minimum one pair of rings need to be configured:
>  - tx: transfer ring and transfer completion ring
>  - rx: free descriptor ring and receive ring
> - two interrupts: UDMA-P channel interrupt and ring interrupt for tc_ring/r_ring
>  - If the channel is in packet mode or configured to memcpy then we only need
>    one interrupt from the ring, events from UDMAP is not used.
> 
> When the channel setup is completed we only interract with the rings:
> - TX: push a descriptor to t_ring and wait for it to be pushed to the tc_ring by
>   the UDMA-P
> - RX: push a descriptor to the fd_ring and waith for UDMA-P to push it back to
>   the r_ring.
> 
> Since we have FIFOs in the DMA fabric (UDMA-P, PSI-L and PDMA) which was not the
> case in previous DMAs we need to report the amount of data held in these FIFOs
> to clients (delay calculation for ALSA, UART FIFO flush support).
> 
> Metadata support:
> DMAengine user driver was posted upstream based/tested on the v1 of the UDMA
> series: https://lkml.org/lkml/2019/6/28/20
> SA2UL is using the metadata DMAengine API.
> 
> Note on the last patch:
> In Keystone2 the networking had dedicated DMA (packet DMA) which is not the case
> anymore and the DMAengine API currently missing support for the features we
> would need to support networking, things like
> - support for receive descriptor 'classification'
>  - we need to support several receive queues for a channel.
>  - the queues are used for packet priority handling for example, but they can be
>    used to have pools of descriptors for different sizes.
> - out of order completion of descriptors on a channel
>  - when we have several queues to handle different priority packets the
>    descriptors will be completed 'out-of-order'
> - NAPI type of operation (polling instead of interrupt driven transfer)
>  - without this we can not sustain gigabit speeds and we need to support NAPI
>  - not to limit this to networking, but other high performance operations
> 
> It is my intention to work on these to be able to remove the 'glue' layer and
> switch to DMAengine API - or have an API aside of DMAengine to have generic way
> to support networking, but given how controversial and not trivial these changes
> are we need something to support networking.
> 
> The series (+DT patch to enabled UDMA/PDMA on AM65x) on top of 5.3-rc2 is
> available:
> https://github.com/omap-audio/linux-audio.git peter/udma/series_v2-5.3-rc2
> 
> Regards,
> Peter
> ---
> Grygorii Strashko (3):
>   bindings: soc: ti: add documentation for k3 ringacc
>   soc: ti: k3: add navss ringacc driver
>   dmaengine: ti: k3-udma: Add glue layer for non DMAengine users
> 
> Peter Ujfalusi (11):
>   dmaengine: doc: Add sections for per descriptor metadata support
>   dmaengine: Add metadata_ops for dma_async_tx_descriptor
>   dmaengine: Add support for reporting DMA cached data amount
>   dmaengine: ti: Add cppi5 header for UDMA
>   dt-bindings: dma: ti: Add document for K3 UDMA
>   dmaengine: ti: New driver for K3 UDMA - split#1: defines, structs, io
>     func
>   dmaengine: ti: New driver for K3 UDMA - split#2: probe/remove, xlate
>     and filter_fn
>   dmaengine: ti: New driver for K3 UDMA - split#3: alloc/free
>     chan_resources
>   dmaengine: ti: New driver for K3 UDMA - split#4: dma_device callbacks
>     1
>   dmaengine: ti: New driver for K3 UDMA - split#5: dma_device callbacks
>     2
>   dmaengine: ti: New driver for K3 UDMA - split#6: Kconfig and Makefile
> 
>  .../devicetree/bindings/dma/ti/k3-udma.txt    |  170 +
>  .../devicetree/bindings/soc/ti/k3-ringacc.txt |   59 +
>  Documentation/driver-api/dmaengine/client.rst |   75 +
>  .../driver-api/dmaengine/provider.rst         |   46 +
>  drivers/dma/dmaengine.c                       |   73 +
>  drivers/dma/dmaengine.h                       |    8 +
>  drivers/dma/ti/Kconfig                        |   22 +
>  drivers/dma/ti/Makefile                       |    2 +
>  drivers/dma/ti/k3-udma-glue.c                 | 1039 +++++
>  drivers/dma/ti/k3-udma-private.c              |  124 +
>  drivers/dma/ti/k3-udma.c                      | 3479 +++++++++++++++++
>  drivers/dma/ti/k3-udma.h                      |  160 +
>  drivers/soc/ti/Kconfig                        |   17 +
>  drivers/soc/ti/Makefile                       |    1 +
>  drivers/soc/ti/k3-ringacc.c                   | 1191 ++++++
>  include/dt-bindings/dma/k3-udma.h             |   10 +
>  include/linux/dma/k3-udma-glue.h              |  125 +
>  include/linux/dma/ti-cppi5.h                  |  996 +++++
>  include/linux/dmaengine.h                     |  110 +
>  include/linux/soc/ti/k3-ringacc.h             |  262 ++
>  20 files changed, 7969 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/dma/ti/k3-udma.txt
>  create mode 100644 Documentation/devicetree/bindings/soc/ti/k3-ringacc.txt
>  create mode 100644 drivers/dma/ti/k3-udma-glue.c
>  create mode 100644 drivers/dma/ti/k3-udma-private.c
>  create mode 100644 drivers/dma/ti/k3-udma.c
>  create mode 100644 drivers/dma/ti/k3-udma.h
>  create mode 100644 drivers/soc/ti/k3-ringacc.c
>  create mode 100644 include/dt-bindings/dma/k3-udma.h
>  create mode 100644 include/linux/dma/k3-udma-glue.h
>  create mode 100644 include/linux/dma/ti-cppi5.h
>  create mode 100644 include/linux/soc/ti/k3-ringacc.h
> 

- Péter

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