[U-Boot] [PATCH v9 0/3] dma: add channels support

28 Nov 2018


      In order to add bcm6348-enet support, dma-uclass must be extended to support
dma channels and reworked to operate like the other dm uclass (clk, reset...).
===
A DMA is a feature of computer systems that allows certain hardware
subsystems to access main system memory, independent of the CPU.
DMA channels are typically generated externally to the HW module
consuming them, by an entity this API calls a DMA provider. This API
provides a standard means for drivers to enable and disable DMAs, and to
copy, send and receive data using DMA.
DMA channel API:
 dma_get_by_index()
 dma_get_by_name()
 dma_request()
 dma_free()
 dma_enable()
 dma_disable()
 dma_prepare_rcv_buf()
 dma_receive()
 dma_send()
A driver that implements UCLASS_DMA is a DMA provider. A provider will
often implement multiple separate DMAs channels, since the hardware it manages
often has this capability. dma_uclass.h describes the interface which
DMA providers must implement.
DMA consumers/clients are the HW modules driven by the DMA channels.
DMA consumer DMA_MEM_TO_DEV (transmit) usage example (based on networking).
Note. In u-boot dma_send() is sync operation always - it'll start transfer and
will poll for it to complete:
- get/request dma channel
    struct dma dma_tx;
    ret = dma_get_by_name(common->dev, "tx0", &dma_tx);
    if (ret) ...
- enable dma channel
    ret = dma_enable(&dma_tx);
    if (ret) ...
- dma transmit DMA_MEM_TO_DEV.
    struct ti_drv_packet_data packet_data;
    
    packet_data.opt1 = val1;
    packet_data.opt2 = val2;
    ret = dma_send(&dma_tx, packet, length, &packet_data);
    if (ret) ..
DMA consumer DMA_DEV_TO_MEM (receive) usage example (based on networking).
Note. dma_receive() is sync operation always - it'll start transfer
(if required) and will poll for it to complete (or for any previously
configured dev2mem transfer to complete):
- get/request dma channel
    struct dma dma_rx;
    ret = dma_get_by_name(common->dev, "rx0", &dma_rx);
    if (ret) ...
- enable dma channel
    ret = dma_enable(&dma_rx);
    if (ret) ...
- dma receive DMA_DEV_TO_MEM.
    struct ti_drv_packet_data packet_data;
    
    len = dma_receive(&dma_rx, (void **)packet, &packet_data);
    if (ret < 0) ...
DMA consumer DMA_DEV_TO_MEM (receive) zero-copy usage example (based on
networking). Networking subsystem allows to configure and use few receive
buffers (dev2mem), as Networking RX DMA channels usually implemented
as streaming interface
- get/request dma channel
    struct dma dma_rx;
    ret = dma_get_by_name(common->dev, "rx0", &dma_rx);
    if (ret) ...
    
    for (i = 0; i < RX_DESC_NUM; i++) {
    	ret = dma_prepare_rcv_buf(&dma_rx,
    				  net_rx_packets[i],
    				  RX_BUF_SIZE);
    	if (ret) ...
    }
- enable dma channel
    ret = dma_enable(&dma_rx);
    if (ret) ...
- dma receive DMA_DEV_TO_MEM.
    struct ti_drv_packet_data packet_data;
    void *packet;
    
    len = dma_receive(&dma_rx, &packet, &packet_data);
    if (ret < 0) ..
    
    /* packet - points on buffer prepared by dma_prepare_rcv_buf().
       process packet*/
    
    - return buffer back to DAM channel
    ret = dma_prepare_rcv_buf(&dma_rx,
    			  net_rx_packets[rx_next],
    			  RX_BUF_SIZE);
===
v9: Separate generic dma channels support from bmips enet support
v8: Sync with latest u-boot.
v7: From Grygorii Strashko:
 - copyright fixed as suggested by Tom Rini
 - added "Reviewed-by" tags
v6: From Grygorii Strashko:
 - added possibility to pass DMA driver/channel's specific data per each
 transfer using additional parameter "metadata" in dma_send/dma_receive() API.
 For example, port number for network packets to be directed to the
 specific port on multi port ethernet controllers.
 - added new dma_prepare_rcv_buf() API which allows to implement zero-copy
 DEV_TO_MEM transfer using DMA streaming channels which is usual case
 for Networking.
 - added dma-uclass test
 - removed unused function dma_get_by_index_platdata()
 - updated comments
v5: Fix build of ti-edma3.
v4: No changes
v3: Introduce changes reported by Simon Glass:
 - Improve dma-uclass.h documentation.
 - Switch to live tree API.
v2: Introduce changes reported by Vignesh:
 - Respect current dma implementation.
 - Let dma_memcpy find a compatible dma device.
Grygorii Strashko (1):
  test: dma: add dma-uclass test
Álvaro Fernández Rojas (2):
  dma: move dma_ops to dma-uclass.h
  dma: add channels support
arch/sandbox/dts/test.dts      |   8 ++
 configs/sandbox_defconfig      |   3 +
 drivers/dma/Kconfig            |  14 ++
 drivers/dma/Makefile           |   1 +
 drivers/dma/dma-uclass.c       | 183 +++++++++++++++++++++++++-
 drivers/dma/sandbox-dma-test.c | 282 +++++++++++++++++++++++++++++++++++++++++
 drivers/dma/ti-edma3.c         |   2 +-
 include/dma-uclass.h           | 128 +++++++++++++++++++
 include/dma.h                  | 282 +++++++++++++++++++++++++++++++++++++----
 test/dm/Makefile               |   1 +
 test/dm/dma.c                  | 123 ++++++++++++++++++
 11 files changed, 997 insertions(+), 30 deletions(-)
 create mode 100644 drivers/dma/sandbox-dma-test.c
 create mode 100644 include/dma-uclass.h
 create mode 100644 test/dm/dma.c
-- 
2.11.0