[PATCH RFC v12 0/7] MPC512x DMA slave s/g support, OF DMA lookup

Alexander Popov a13xp0p0v88 at gmail.com
Wed Apr 23 23:53:22 EST 2014

2013/7/14 Gerhard Sittig <gsi at denx.de>:
> this series
> - introduces slave s/g support (that's support for DMA transfers which
>    involve peripherals in contrast to mem-to-mem transfers)
> - adds device tree based lookup support for DMA channels
> - combines floating patches and related feedback which already covered
>    several aspects of what the suggested LPB driver needs, to demonstrate
>    how integration might be done
> - carries Q&D SD card support to enable another DMA client during test,
>    while this patch needs to get dropped upon pickup

Changes in v2:
> - re-order mpc8308 related code paths for improved readability, no
>    change in behaviour, introduction of symbolic channel names here
>    already
> - squash 'execute() start condition' and 'terminate all' into the
>    introduction of 'slave s/g prep' and 'device control' support; refuse
>    s/g lists with more than one item since slave support is operational
>    yet proper s/g support is missing (can get addressed later)
> - always start transfers from software on MPC8308 as there are no
>    external request lines for peripheral flow control
> - drop dt-bindings header file and symbolic channel names in OF nodes

Changes in v3 and v4:
 Part 1/5:
 - use #define instead of enum since individual channels don't require
    special handling.
 Part 2/5:
 - add a flag "will_access_peripheral" to DMA transfer descriptor
    according recommendations of Gerhard Sittig.
    This flag is set in mpc_dma_prep_memcpy() and mpc_dma_prep_slave_sg()
    and is evaluated in mpc_dma_execute() to choose a type of start for
    the transfer.
 - prevent descriptors of transfers which involve peripherals from
    being chained together;
    each of such transfers needs hardware initiated start.
 - add locking while working with struct mpc_dma_chan
    according recommendations of Lars-Peter Clausen.
 - remove default nbytes value. Client kernel modules must set
    src_maxburst and dst_maxburst fields of struct dma_slave_config (dmaengine.h).

Changes in v5:
 Part 2/5:
 - add and improve comments;
 - improve the code moving transfer descriptors from 'queued' to 'active' list
    in mpc_dma_execute();
 - allow mpc_dma_prep_slave_sg() to run with non-empty 'active' list;
 - take 'mdesc' back to 'free' list in case of error in mpc_dma_prep_slave_sg();
 - improve checks of the transfer parameters;
 - provide the default value for 'maxburst' in mpc_dma_device_control().

Changes in v6:
 Part 2/5:
 - remove doubtful comment;
 - fix coding style issues;
 - set default value for 'maxburst' to 1 which applies to most cases;
 Part 3/5:
 - use dma_get_slave_channel() instead of dma_request_channel()
    in new function of_dma_xlate_by_chan_id() according recommendations of
    Arnd Bergmann;
 Part 4/5:
 - set DMA_PRIVATE flag for MPC512x DMA controller since its driver relies on
    of_dma_xlate_by_chan_id() which doesn't use dma_request_channel()
    any more; (removed in v7)
 - resolve little patch conflict;
 Part 5/5:
 - resolve little patch conflict;

Changes in v7:
 Part 2:
 - improve comment;
 Part 4:
 - split in two separate patches. Part 4/6 contains device tree
    binding document and in part 5/6 MPC512x DMA controller is registered
    for device tree channel lookup;
 - remove setting DMA_PRIVATE flag for MPC512x DMA controller from part 5/6;

Changes in v8:
 Part 2:
 - improve comments;
 - fix style issues;
 Part 6:
 - remove since it has become obsolete;

Changes in v9:
 A new patch (part 3/6) is added to this series according the
   feedback of Andy Shevchenko.
 Part 2/6:
 - keep style of the comments;
 - use is_slave_direction() instead of manual checks;
 - remove redundant else branches of the conditions;
 - make mpc_dma_device_control() return -ENXIO for unknown command;
 Part 6/6:
 - change according the new part 3/6;
 - fix style issues;

Changes in v10:
 Part 2/6:
 - don't use direction field of dma_slave_config in mpc_dma_device_control()
    but store settings in mpc_dma_chan for both DMA_DEV_TO_MEM and
    DMA_MEM_TO_DEV cases; then retrieve the needed values in
 - fix style issue and put 2014 instead of 2013;
 Part 3/6:
 - fix mpc_dma_probe() error path and mpc_dma_remove(): manually free IRQs and
    dispose IRQ mappings before devm_* takes care of other resources;
 Part 6/6:
 - change according the new part 3/6;
 - fix style issue;

Changes in v11:
 Part 5/6:
 - remake device tree binding document according the recommendations of
    Gerhard Sittig, Mark Rutland and Arnd Bergmann;

Changes in v12:
 A new patch (part 2/7) is added to this series.
 Part 6/7:
 - change the description of 'compatible' property according part 2/7;
 - improve the document according Gerhard's feedback;

> known issues:
> - it's yet to get confirmed whether MPC8308 can use slave support or
>    whether the DMA controller's driver shall actively reject it, the
>    information that's available so far suggests that peripheral transfers
>    to IP bus attached I/O is useful and shall not get blocked right away
 - adding support for transfers which don't increment the RAM address or
    do increment the peripheral "port's" address is easy with
    this implementation; but which options of the common API
    should be used for specifying such transfers?

Alexander Popov (7):
  dma: mpc512x: reorder mpc8308 specific instructions
  dma: mpc512x: separate 'compatible' values for MPC512x and MPC8308
  dma: mpc512x: add support for peripheral transfers
  dma: mpc512x: fix freeing resources in mpc_dma_probe() and
  dma: of: add common xlate function for matching by channel id
  dma: mpc512x: add device tree binding document
  dma: mpc512x: register for device tree channel lookup

 .../devicetree/bindings/dma/mpc512x-dma.txt        |  40 +++
 arch/powerpc/boot/dts/mpc5121.dtsi                 |   1 +
 arch/powerpc/boot/dts/mpc8308_p1m.dts              |   2 +-
 arch/powerpc/boot/dts/mpc8308rdb.dts               |   2 +-
 drivers/dma/mpc512x_dma.c                          | 346 ++++++++++++++++++---
 drivers/dma/of-dma.c                               |  35 +++
 include/linux/of_dma.h                             |   4 +
 7 files changed, 390 insertions(+), 40 deletions(-)
 create mode 100644 Documentation/devicetree/bindings/dma/mpc512x-dma.txt


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