Hi Steve, On Tue, May 5, 2015 at 10:36 AM, Opensource [Steve Twiss] <stwiss.opensource@xxxxxxxxxxx> wrote: > On 04 May 2015 08:47, Geert Uytterhoeven wrote: >> On Thu, Apr 30, 2015 at 1:26 PM, S Twiss <stwiss.opensource@xxxxxxxxxxx> >> wrote: >> > Add MFD support for the DA9063 OnKey driver >> > +static int da9063_clear_fault_log(struct da9063 *da9063) >> > +{ >> > +} >> > + >> > int da9063_device_init(struct da9063 *da9063, unsigned int irq) >> > { >> > struct da9063_pdata *pdata = da9063->dev->platform_data; >> > int model, variant_id, variant_code; >> > int ret; >> > >> > + ret = da9063_clear_fault_log(da9063); >> > + if (ret < 0) >> > + dev_err(da9063->dev, "Cannot clear fault log\n"); >> > + >> > if (pdata) { >> > da9063->flags = pdata->flags; >> > da9063->irq_base = pdata->irq_base; >> >> The code above doesn't seem to match the patch description. >> Can you please explain why it is needed? > > Yes, at first it does seem that the fault-log clearing function is unrelated to the > "MFD support for the DA9063 OnKey driver", but there is an important connection > that makes it essential for the OnKey driver in this case. > > I have made some explanation of the OnKey's operation in this thread here: > https://lkml.org/lkml/2015/4/29/406 > > But I only described the OnKey's point-of-view for case (4) of the "OnKey operation" > Case (4): the long-long press and no key release -- the hardware power-cut when > software is unable to respond (for whatever reason). > > In this case, if the software was not responsive and a hardware shutdown of the > device was chosen, the FAULT_LOG would persist with information that would be > accessible when the device was restarted: it would be possible to take action the > next time the device was turned on again (maybe to trigger some mitigation exercise > in the bootloader -- e.g. say to complete memory checks or put the device into a > safe mode). > > However this mitigation exercise and clearance of the fault-log cannot be counted on > outside the Linux kernel and so the clearance function da9063_clear_fault_log () has > been done here. > > If this clearance function did not exist, then after a hardware shutdown (due to S/W > failure), the next time the device is restarted the FAULT_LOG would persist with values > from the previous error. Thanks for your explanation! Please add (some parts of it) to the patch description. Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds -- 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