On Mon, Feb 5, 2018 at 11:09 AM, Lucas Stach <l.stach@xxxxxxxxxxxxxx> wrote: >> > +Optional Properties: >> > +- drive-strength Integer: controls Drive Strength >> >> I thought drive-strength is supposed to be be in mA. We should not have >> differing units in common properties. >> >> There was an Atmel binding the other day that this came up. > > I know it's in the common binding, but it's going to be very hard to > support. The drive-strength in mA really depends on external loading of > the pin and the pin voltage, at least for the most widespread > controllers that only switch between resistors, instead of driving the > pin by a current regulator. How does this circuit really look? Can you sketch something so we understand what is going on electronically here? The way I imagine most drive strength out there works is by simply connection more MOS-totempoles after each other and each of them has a production-technology-related max output current like 4mA, so by putting two in a series yoy double that to 8 mA. Is that what you mean with "current regulator"? If you mean rather "output impedance", that is something else and something we need a new (generic) property for. I never saw that before, really. > I would much prefer if we just remove unit from the common binding and > let the drivers define it in a way that fits their hardware > description. Yeah but is this really the same thing even ... > It's the same thing with the slew-rate really, but the common binding > didn't make the mistake to define a single unit there, with many > pincontrollers being really vague about how fast the slew really is, > but some may actually define it in uS or whatever else makes sense. I agree with that. Also for skewrate and output time delays (skew delay). It's very unclear how cell libraries really implement this. But with drive strength I thought we knew it ... Yours, Linus Walleij -- 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
