On 15 May 2017 at 18:16, Rob Herring <robh@xxxxxxxxxx> wrote: > On Mon, May 15, 2017 at 6:08 AM, Ulf Hansson <ulf.hansson@xxxxxxxxxx> wrote: >> On 12 May 2017 at 22:03, Rob Herring <robh@xxxxxxxxxx> wrote: >>> On Mon, May 08, 2017 at 06:21:10PM +0200, Ulf Hansson wrote: >>>> During power off, after the GPIO pin has been asserted, some devices like >>>> the Wifi chip from TI, Wl18xx, needs a delay before the host continues with >>>> clock gating and turning off regulators as to follow a graceful shutdown >>>> sequence. >>>> >>>> Therefore invent an optional power-off-delay-us DT binding for >>>> mmc-pwrseq-simple, to allow us to support this constraint. >>> >>> Do you really need this to be programmable per device. A delay is not >>> going to hurt devices that don't need it. >> >> Well, that depends on what "hurt" means. The device would still be >> properly shut down, only that it would take unnecessary longer to do >> so. >> >> I think the problem here, is that this delay may also affect system >> suspend/resume time of the device, if the device powers off/on in this >> sequence. > > I was assuming that given you changed the units the time was small > enough to not be significant. That's right. We are in the range of < 50us, which is suitable for the Wl18xx chip. However, the problem occurs when some other device needs a longer delay and then we may reach a threshold that isn't acceptable. To me it's better to allow it to be described in DT - then only influencing those devices that really needs it. > >>> Sorry, but this is exactly what I don't like about "simple" bindings: >>> adding one property at a time. >> >> I understand you opinion, which in the end is a matter of taste/flavor. > > It's more than that. The problem is you would end up with a different > binding if everything is defined up front versus reviewing one > addition at a time. > > To give a trivial example here, now we have power on and off times in > different units and if I was reviewing them together I would say make > them both usec. That example is mostly taste, but different units also > makes it more error prone for the dts writer. Okay, I see your a point. > >> However, for me this just follows the existing approach - and suddenly >> say no to this, doesn't really seems right either. > > I never said no. Alright. Is that a yes then? :-) If not, what do you prefer me to do? Kind regards Uffe -- 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
