> Am 28.06.2017 um 12:50 schrieb Sylwester Nawrocki <s.nawrocki@xxxxxxxxxxx>: > > On 06/28/2017 11:12 AM, H. Nikolaus Schaller wrote: >>> Am 28.06.2017 um 00:57 schrieb Sylwester Nawrocki <snawrocki@xxxxxxxxxx>: >>> On 06/27/2017 07:48 AM, H. Nikolaus Schaller wrote: >>>>> Am 26.06.2017 um 22:04 schrieb Sylwester Nawrocki <snawrocki@xxxxxxxxxx>: >>>>> On 06/26/2017 12:35 PM, Hugues FRUCHET wrote: >>>>>>> What I am missing to support the GTA04 camera is the control of the optional "vana-supply". >>>>>>> So the driver does not power up the camera module when needed and therefore probing fails. >>>>>>> >>>>>>> - vana-supply: a regulator to power up the camera module. >>>>>>> >>>>>>> Driver code is not complex to add: >>>>> >>>>>> Yes, I saw it in your code, but as I don't have any programmable power >>>>>> supply on my setup, I have not pushed this commit. >>>>> >>>>> Since you are about to add voltage supplies to the DT binding I'd suggest >>>>> to include all three voltage supplies of the sensor chip. Looking at the OV9650 >>>>> and the OV9655 datasheet there are following names used for the voltage supply >>>>> pins: >>>>> >>>>> AVDD - Analog power supply, >>>>> DVDD - Power supply for digital core logic, >>>>> DOVDD - Digital power supply for I/O. >>>> >>>> The latter two are usually not independently switchable from the SoC power >>>> the module is connected to. >>>> >>>> And sometimes DVDD and DOVDD are connected together. >>>> >>>> So the driver can't make much use of knowing or requesting them because the >>>> 1.8V supply is always active, even during suspend. >>>> >>>>> >>>>> I doubt the sensor can work without any of these voltage supplies, thus >>>>> regulator_get_optional() should not be used. I would just use the regulator >>>>> bulk API to handle all three power supplies. >>>> >>>> The digital part works with AVDD turned off. So the LDO supplying AVDD should >>>> be switchable to save power (&vaux3 on the GTA04 device).> >>>> But not all designs can switch it off. Hence the idea to define it as an >>>> /optional/ regulator. If it is not defined by DT, the driver simply assumes >>>> it is always powered on. >>> >>> I didn't say we can't define regulator supply properties as optional in the DT >>> binding. If we define them as such and any of these *-supply properties is >>> missing in DT with regulator_get() the regulator core will use dummy regulator >>> for that particular voltage supply. While with regulator_get_optional() >>> -ENODEV is returned when the regulator cannot be found. >> >> Ah, ok. I see. >> >> I had thought that it is the right thing to do like devm_gpiod_get_optional(). >> >> That one it is described as: >> >> "* This is equivalent to gpiod_get(), except that when no GPIO was assigned to >> * the requested function it will return NULL. This is convenient for drivers >> * that need to handle optional GPIOs." >> >> Seems to be inconsistent definition of what "optional" means. > > Indeed, this commit explains it further: > > commit de1dd9fd2156874b45803299b3b27e65d5defdd9 > regulator: core: Provide hints to the core about optional supplies > >> So we indeed should use devm_regulator_get() in this case. Thanks for > pointing out! > >>>> So in summary we only need AVDD switched for the GTA04 - but it does not >>>> matter if the others are optional properties. We would not use them. >>>> >>>> It does matter if they are mandatory because it adds DT complexity (size >>>> and processing) without added function. >>> >>> We should not be defining DT binding only with selected use cases/board >>> designs in mind. IMO all three voltage supplies should be listed in the >>> binding, presumably all can be made optional, with an assumption that when >>> the property is missing selected pin is hooked up to a fixed regulator. >> >> Ok, then it should just be defined in the bindings but not used by >> the driver? > > Yes, I think so. So we have a possibly complete binding right from the > beginning. I someone needs handling other supplies than AVDD they could > update the driver in future. Fine! I have sent some patches to Hughues so that he can integrate it in his next version of the patch series. BR and thanks, Nikolaus -- 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
