[PATCH v4 0/2] Add support for multiple coherent memory regions

[Howard Yen <howardyen@google.com>]

In the system I'm working on, there is an always-on subsystem which
includes a small size memory, and several functions need to run and
occupy the memory from the small memory if they need to run on the
always-on subsystem. These functions must allocate the memory from the
small memory region, so that they can get benefit from the always-on
subsystem. So the small memory is split for multiple functions which are
satisfied with their generic use cases. But in specific use cases, like
USB3 devices which support the stream trasnsfer or multiple devices
connect to the host, they required more memory than their pre-allocated
memory region. I tried to implement it in a generic way and propose this
patch to give it the ability to get the memory from the other larger
memory to solve the issue.


Changelog
--------------------------------------------
Changes in v4:
- Add the driver where uses the multiple coherent memory regions

Changes in v3:
- Re-org the members of struct dma_coherent_mem to avoid additional
  pointer arithmetics and the holes inside the structure.
- Use consistent naming of return value.
- Re-write the dev checking statement to be more clear.

Changes in v2:
- Replace the pointer(dma_mem) to a list_head(dma_mems) in the device
  structure and initialize the list_head in device_initialize().
- Modify the required changes in coherent.c.


Howard Yen (2):
  dma-coherent: add support for multi coherent rmems per dev
  usb: host: xhci-plat: add support for multi memory regions

 drivers/base/core.c          |  3 ++
 drivers/usb/host/xhci-plat.c | 19 +++++++-
 include/linux/device.h       |  5 +-
 kernel/dma/coherent.c        | 92 +++++++++++++++++++++++-------------
 4 files changed, 82 insertions(+), 37 deletions(-)

-- 
2.44.0.278.ge034bb2e1d-goog