Sylwester Nawrocki wrote: > On 08/18/2011 09:02 PM, Sakari Ailus wrote: >>>>>> >>>>>> He-h, I guess you are not going to apply this one. >>>>>> The patch breaks init logic of the device. If we have no ->power(), we >>>>>> still need to bring the device to the known state. I have no good idea >>>>>> how to do this. >>>>> >>>>> I don't think it breaks anything actually. Albeit in practice one is still >>>>> likely to put the adp1653 reset line to the board since that lowers its power >>>>> consumption significantly. >>>> Yeah, even in practice we might see various ways of a chip connection. >>>> >>>>> Instead of being in power-up state after opening the flash subdev, it will >>>>> reach this state already when the system is powered up. At subdev open all >>>>> the relevant registers are written to anyway, so I don't see an issue here. >>>> You mean at first writing to the V4L2 value, do you? Because ->open() >>>> uses set_power() which will be skipped in case of no ->power method >>>> defined. >>>> >>>>> I think either this one, or one should check in probe() that the power() >>>>> callback is non-NULL. >>>>> The board code is going away in the near future so this callback will >>>>> disappear eventually anyway. >>>> So, it's up to you to include or not my last patch. >>>> >>>>> The gpio code in the board file should likely >>>>> be moved to the driver itself. >>>> The line could be different, the hw could be used in environment w/o >>>> gpio, but with (for example) external gate, and so on. I think current >>>> generic driver is pretty okay. >>> >>> Would it make sense to use the regulator API in place of the platform_data >>> callback? If there is only one GPIO then it's easy to create a 'fixed voltage >>> regulator' for this. >> >> I don't know the regulator framework very well, but do you mean creating a new >> regulator which just controls a gpio? It would be preferable that this wouldn't >> create a new driver nor add any board core. > > I'm afraid your requirements are too demanding :) > Yes, I meant creating a new regulator. In case the ADP1635 voltage regulator > is inhibited through a GPIO at a host processor such regulator would in fact > be only flipping a GPIO (and its driver would request the GPIO and set it into > a default inactive state during its initialization). But the LDO for ADP1635 Thinking about this again, I think we'd need a regulator and reset gpio. The reset line probably can't be really modelled as a power supply, as the voltage provided to the chip is different from the reset line. Both may exist on some boards. The regulator might be a dummy one, too, as well as the reset line. > could be also a part of larger PMIC device, which are often configured through > I2C and have their generic drivers (in drivers/regulator). So the regulator API > in some extent abstracts the power supply details. There is a common API at the > client driver side regardless of the details how the power is actually enabled/ > disabled. > > I've seen some patches for the device tree bindings for the regulator API > but I guess this is not in the mainline yet. > > Currently the 'fixed voltage regulator' is instantiated by creating a platform > device, with an appropriate 'id', in the board code. And you have to create... > a platform data for it :) The driver is common for all such devices > (drivers/regulator/fixed.c). I'll take a look at that. >>> Does the 'platform_data->power' callback control power supply on pin 14 (VDD) >>> or does it do something else? >> >> No. The chip is always powered on the N900 but pulling down (or up, I don't remember) >> its reset pin puts the chip to reset and causes the current draw to reach almost zero. >> I think it's in the class of some or few tens of µA. Someone still might implement > > According to the datasheet it's even less, below 1 uA :) Right. That indeed was probably the reason there was no need for a controllable regulator. > "Shutdown Current (EN = GND, TJ = −40°C to +85°C) = 0.1μA (Typ.), 1μA (Max)" > > So the reset (EN) pin is basically a GPIO, but it could be as well some signal > provided by a glue FPGA, driven by a memory mapped register(s). > Then the callback is most flexible, but it's a little bit ugly at the same time:) > If I were you I, would probably originally put a GPIO number in platform_data, > instead of a function callback. But that depends on priorities. > >> a board containing the adp1653 which would require enabling a regulator for it. > > Indeed, I guess there is no point in adding support for the power supply control > over the regulator API now. When someone needs it on some other board, it can > be added in the driver then. I fully agree. -- Sakari Ailus sakari.ailus@xxxxxx -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
