Hi, On Tue, 2014-12-09 at 12:20 +0100, Arnd Bergmann wrote: > On Tuesday 09 December 2014 11:30:15 Matthias Brugger wrote: > > 2014-12-09 11:13 GMT+01:00 Sascha Hauer <s.hauer@xxxxxxxxxxxxxx>: > > > On Tue, Dec 09, 2014 at 09:23:18AM +0100, Arnd Bergmann wrote: > > >> > > >> I think we have had a similar case recently where a controller wasn't > > >> actually using I2C, but the sofware protocol was close enough so we decided > > >> to make it appear as i2c in Linux. > > >> > > >> Would that work for you, i.e. register the pmic wrapper as a fake spi > > >> master driver in drivers/spi/ and register the rtc/regulator/codec > > >> as SPI clients from DT? > > > > > > I don't think that's appropriate. I mean technically that could even > > > work, but in software you really don't see anything from the underlying > > > SPI bus. The SoC and the PMIC are really tightly coupled via the PMIC > > > wrapper. This goes to the point where pins of the SoCs internal I2C and > > > keypad controllers are routed over the SPI bus out of the PMIC. In > > > software you do this by setting a bit in the I2C controller. If it's > > > set, the signals are routed out of the PMIC instead of the main die. > > > As said, technically we probably could create a fake SPI master, but > > > that wouldn't really fit to this situation. > > Ok, I see. > > > I agree with Sascha. Although from the hardware point of view, the > > communication between the PMIC and the SOC is done through SPI from > > the point of view of the software everything looks like I2C commands > > which will be "transalted" into SPI messages by the PMIC wrapper. > > If it looks like i2c messages, would it be more appropriate to make > it appear as an i2c controller then? Although the message looks like I2C command, it is not I2C. Form source code, the software does not touch any I2C i/o or protocols. It depends SoC and has specific initial flow, read and write transfer state. It is not able to an i2c controller. That's why we consider its a proprietary hardware with specific protocols. How about let it appear in driver/soc? Thanks, Flora -- 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
