On Thu, Sep 25, 2014 at 11:27 AM, Mark Rutland <mark.rutland@xxxxxxx> wrote: > On Wed, Sep 24, 2014 at 07:59:34PM +0100, Frans Klaver wrote: >> On Wed, Sep 24, 2014 at 04:34:32PM +0100, Mark Rutland wrote: >> > On Wed, Sep 24, 2014 at 04:14:48PM +0100, Frans Klaver wrote: >> > > On Wed, Sep 24, 2014 at 03:38:49PM +0100, Mark Rutland wrote: >> > > > On Wed, Sep 24, 2014 at 03:22:22PM +0100, Frans Klaver wrote: >> > > > You mention that there's a GPIO that can be used to detect the battery >> > > > presence. Why can't the driver always probe and then on check for the >> > > > presence of the battery dynamically using that GPIO? That should cover >> > > > both cases. >> > > >> > > I would say that this was the case before [1] was done. The GPIO is >> > > optional and if not configured, the presence or absence of the battery >> > > is detected by checking a status register much like probe() currently >> > > does. It seems all cases were covered before that patch. If you worry >> > > about speed, you should use the GPIO. I wonder if we might be able to >> > > revert [1] without doing much harm. >> > >> > But reverting that would re-introduce the lag on some systems, no? Given >> > the wording of the original commit I would guess that the GPIO wasn't >> > available. Perhaps Olof or Anton can enlighten us? >> >> It probably would yes. The battery_detect gpio was last touched in 2011, the >> probe check was added somewhere in 2012. > > We can't revert it unless we know doing so won't reintroduce the > problem. From the above it sounds like we can't revert it. > >> We could keep it as a compile option. > > Perhaps. > >> > In the cases where a GPIO is available, I think we should be able to be >> > less pessimistic. Is a GPIO available in your case? >> >> We don't have the battery_detect pin available. Incidentally, a bit of >> lag reading out the battery is not a problem for us. > > So now we're back at sqaure one. The hardware is likely identical in the > your case and the care-about-lag case. Whether or not you care about lag > is a property of the user rather than the HW, so I don't think that > belongs in the dt. > > It would be interesting to know what the lag was adversely affecting. > Perhaps there's another way around this. Exactly. I can imagine this really being a problem if the i2c bus already has a lot of priority traffic. Frans -- 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
