[PATCH v4 0/5] spi: Add DMA mode support to spi-qcom-qspi

[Vijaya Krishna Nivarthi]

There are large number of QSPI irqs that fire during boot/init and later
on every suspend/resume.
This could be made faster by doing DMA instead of PIO.
Below is comparison for number of interrupts raised in 2 scenarios...
Boot up and stabilise
Suspend/Resume

Sequence   PIO    DMA
=======================
Boot-up    69088  19284
S/R        5066   3430

Speed test results...
spi-nor read times in sec after 2 min uptime
============================================
PIO - Iterations-1000, min=3.18, max=3.74, avg=3.53
DMA - Iterations-1000, min=1.21, max=2.28, avg=1.79

spi-nor write times in sec after 2 min uptime
=============================================
PIO - Iterations-1000, min=3.20, max=8.24, avg=3.58
DMA - Iterations-1000, min=1.25, max=5.13, avg=1.82

Further testing performed...
a) multiple entries in sgt (simulated by max_dma_len = 1024)
b) fallback to pio (simulated by dma setup failure)

Vijaya Krishna Nivarthi (5):
  spi: dt-bindings: qcom,spi-qcom-qspi: Add iommus
  arm64: dts: qcom: sc7180: Add stream-id of qspi to iommus
  arm64: dts: qcom: sc7280: Add stream-id of qspi to iommus
  arm64: dts: qcom: sdm845: Add stream-id of qspi to iommus
  spi: spi-qcom-qspi: Add DMA mode support
---
v3 -> v4:
- Dropped unaligned dma buffer handling
- Added sdm845, sc7180 dtsis to the series

v2 -> v3:
- Modified commit messages
- Made a change to driver based on re-review

v1 -> v2:
- Added documentation file to the series
- Made changes to driver based on HPG re-review
---
 .../bindings/spi/qcom,spi-qcom-qspi.yaml           |   3 +
 arch/arm64/boot/dts/qcom/sc7180.dtsi               |   1 +
 arch/arm64/boot/dts/qcom/sc7280.dtsi               |   1 +
 arch/arm64/boot/dts/qcom/sdm845.dtsi               |   1 +
 drivers/spi/spi-qcom-qspi.c                        | 292 +++++++++++++++++++--
 5 files changed, 271 insertions(+), 27 deletions(-)

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