[rtc-linux] Re: [PATCH v2 1/2] rtc: ds1302: add register access abstraction layer

[Sergei Ianovich <ynvich@gmail.com>]

On Mon, 2016-06-27 at 20:19 +0900, Akinobu Mita wrote:
> The rtc-ds1302 driver now implemented using SPI 3wire mode.
> But I would like to access it with using three wires connected to
> GPIO
> lines.
>=20
> This adds abstraction layer for DS1302 register access in order to
> prepare to support for using GPIO lines.=C2=A0=C2=A0This enables to share
> common
> code between SPI driver and GPIO driver.

I don't think this is the right way. DS-1302 is an SPI device, not a
GPIO one. It can be connected to a hardware SPI controller or a
software one (on top of GPIO or memory).

Your patch re-adds Microwire SPI control logic to RTC subsystem, which
was cleared by my rewrite of drivers/rtc/rtc-ds1302.c. The logic is
already present in=C2=A0bitbang_txrx_be_cpha0_lsb() in=C2=A0drivers/spi/spi=
-
lp8841-rtc.c.

I still think you need to implement=C2=A0spi-gpio-3wire with LSB-first
support in SPI subsystem instead. It wasn't done when I was adding
LP8841 support, because LP8841 was the only use case of Microwire SPI
control logic. If you add it, drivers/spi/spi-lp8841-rtc.c can be
removed and replaced by a GPIO driver to host a new spi-gpio-3wire
device.

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