[v2,0/6] gpio: dwapb: Fix reference clocks usage

From: Serge Semin <fancer.lancer@gmail.com>

There is no need in any fixes to have the Baikal-T1 SoC DW GPIO controllers
supported by the kernel DW APB GPIO driver. It works for them just fine with
no modifications. But still there is a room for optimizations there.

First of all as it tends to be traditional for all Baikal-T1 SoC related
patchset we replaced the legacy plain text-based dt-binding file with
yaml-based one. Baikal-T1 DW GPIO port A supports a debounce functionality,
but in order to use it the corresponding reference clock must be enabled.
We added support of that clock in the driver and made sure the dt-bindings
had its declaration. In addition seeing both APB and debounce reference
clocks are optional, we replaced the standard devm_clk_get() usage with
the function of optional clocks acquisition.

This patchset is rebased and tested on the mainline Linux kernel 5.6-rc4:
commit 98d54f81e36b ("Linux 5.6-rc4").

Changelog v2:
- Use a shorter summary describing the DT bindings conversion patch.
- Add myself to the MAINTAINERS file as a maintainer of the DW APB GPIO driver.
- Add myself to the maintainers list of the DW APB GPIO driver DT schema.
- Print error instead of info-message if APB/debounce clocks either
  failed to be acquired or couldn't be enabled.
- Rearrange the SoB tags.
- Make sure DT schema defines the lowercase hex numbers in the main dt-node
  name and in the sub-node names.
- Use "allOf:" statement to apply uint32 and "minimum/maximum" limitations
  on the "snps,nr-gpios" property of the DW APB GPIO DT schema.
- Discard "interrupts-extended" property from the DT schema.
- Make sure the sub-nodes have names with either 'gpio-port' or
  'gpio-controller' prefixes.
- Our corporate email server doesn't change Message-Id anymore, so the patchset
  is resubmitted being in the cover-letter-threaded format.

Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Cc: Alexey Malahov <Alexey.Malahov@baikalelectronics.ru>
Cc: Maxim Kaurkin <Maxim.Kaurkin@baikalelectronics.ru>
Cc: Pavel Parkhomenko <Pavel.Parkhomenko@baikalelectronics.ru>
Cc: Ramil Zaripov <Ramil.Zaripov@baikalelectronics.ru>
Cc: Ekaterina Skachko <Ekaterina.Skachko@baikalelectronics.ru>
Cc: Vadim Vlasov <V.Vlasov@baikalelectronics.ru>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Paul Burton <paulburton@kernel.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Hoan Tran <hoan@os.amperecomputing.com>
Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Cc: Philipp Zabel <p.zabel@pengutronix.de>
Cc: Rob Herring <robh+dt@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: linux-gpio@vger.kernel.org
Cc: devicetree@vger.kernel.org
Cc: linux-kernel@vger.kernel.org

Serge Semin (6):
  dt-bindings: gpio: Convert snps,dw-apb-gpio to DT schema
  dt-bindings: gpio: Add DW GPIO debounce clock property
  dt-bindings: gpio: Add Sergey Semin to DW APB GPIO driver maintainers
  gpio: dwapb: Use optional-clocks interface for APB ref-clock
  gpio: dwapb: Add debounce reference clock support
  MAINTAINERS: Add Segey Semin to maintainers of DW APB GPIO driver

 .../bindings/gpio/snps,dw-apb-gpio.yaml       | 134 ++++++++++++++++++
 .../bindings/gpio/snps-dwapb-gpio.txt         |  65 ---------
 MAINTAINERS                                   |   1 +
 drivers/gpio/gpio-dwapb.c                     |  41 ++++--
 4 files changed, 161 insertions(+), 80 deletions(-)
 create mode 100644 Documentation/devicetree/bindings/gpio/snps,dw-apb-gpio.yaml
 delete mode 100644 Documentation/devicetree/bindings/gpio/snps-dwapb-gpio.txt