On 27/06/2016 at 14:50:49 +0300, Sergei Ianovich wrote : > 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. > > > > This adds abstraction layer for DS1302 register access in order to > > prepare to support for using GPIO lines. This 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 bitbang_txrx_be_cpha0_lsb() in drivers/spi/spi- > lp8841-rtc.c. > > I still think you need to implement spi-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. Well, back in April, we concluded it was not easily doable after discussing with Mark and there was still issues after implementing it in spi-gpio. My understanding is that while microwire seems compatible with SPI mode 0, it actually isn't and this should be treated as a different mode. If we want to do something generic, I think we should have a microwire-gpio driver. Maybe in the SPI subsystem? How do yo currently select microwire mode for PX270? -- Alexandre Belloni, Free Electrons Embedded Linux, Kernel and Android engineering http://free-electrons.com -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
