[PATCH 0/3] spi: cadence-xspi: add DMA support

[Jisheng Zhang <jszhang@kernel.org>]

This series tries to improve the cadence-xspi cpu usage and potential
performance if the allocated dmaengine is powerful.

But no matter the dmaengine performance is powerful or not, the cpu
usage is reduced a lot.

For example, on a dual CA55 platform, test with looping the following
cmd:
dd if=/dev/mtd0 of=/dev/null bs=8192

Before the patch:
cpu usage is nearly 50%, which means one CA55 is full loaded with
the sdma io copy.

After the patch:
cpu usage is between 0 ~ 1%

patch1 documents the dt-binding
patch2 adds the memcpy dmaengine support 
patch3 uses writel_relaxed for cmd regs.

Jisheng Zhang (3):
  spi: dt-bindings: cdns,xspi: Add DMA properties
  spi: cadence-xspi: Support dmaengine for sdma io copy
  spi: cadence-xspi: Use writel_relaxed() for cmd regs

 .../devicetree/bindings/spi/cdns,xspi.yaml    |  13 ++
 drivers/spi/spi-cadence-xspi.c                | 149 +++++++++++++++++-
 2 files changed, 155 insertions(+), 7 deletions(-)

-- 
2.55.0