[PATCH 0/2] gpio: dwapb: add native hardware both-edge support

[Guohao Zhang]

Some DW APB GPIO IP instances are synthesized with the GPIO_INT_BOTH_EDGE
feature, which adds the GPIO_INT_BOTHEDGE register to latch both signal
edges of a line in hardware.

This series adds support for it to the driver:

  patch 1 adds the device tree property "snps,native-both-edge" that marks
          a controller whose IP instance provides the register.
  patch 2 makes the driver use the hardware register for IRQ_TYPE_EDGE_BOTH
          when the property is present, and keeps the existing software
          polarity toggle otherwise.

The capability is per-IP-instance rather than per-SoC, so it is described in
the device tree instead of being selected by a build-time option, which in a
multiplatform kernel could not express a per-controller difference.

Register 0x68 is only accessed when the property is present; for controllers
without it the driver behaviour is unchanged and no access to 0x68 is emitted.

The change was measured on a Horizon Robotics J6P board. In a high-rate edge
test the software polarity-toggle implementation lost about 2% of the
interrupts, while the native both-edge mode lost none. With the flag off, the
built object contains no access to offset 0x68 and the software path is
unchanged.

Guohao Zhang (2):
  dt-bindings: gpio: dwapb: add snps,native-both-edge
  gpio: dwapb: support native hardware both-edge detection

 .../bindings/gpio/snps,dw-apb-gpio.yaml       | 10 ++++
 drivers/gpio/gpio-dwapb.c                     | 49 +++++++++++++++++--
 2 files changed, 56 insertions(+), 3 deletions(-)

-- 
2.34.1