Re: [PATCH 4/4] rtc: isl1208: add support for isl1219 with hwmon for tamper detection

[Rob Herring <robh@kernel.org>]

On Tue, Jan 30, 2018 at 2:56 AM, Denis OSTERLAND
<denis.osterland@diehl.com> wrote:
> Am Montag, den 29.01.2018, 17:41 -0600 schrieb Rob Herring:
>> On Tue, Jan 23, 2018 at 01:18:01PM +0100, Michael Grzeschik wrote:
>> >
>> > We add support for the ISL1219 chip that got an integrated tamper
>> > detection function. This patch implements the feature by using an hwmon
>> > interface.
>> >
>> > The ISL1219 can also describe the timestamp of the intrusion
>> > event. For this we add the documentation of the new interface
>> > intrusion[0-*]_timestamp.
>> >
>> > The devicetree documentation for the ISL1219 device tree
>> > binding is added with an short example.
>> >
>> > Signed-off-by: Michael Grzeschik <m.grzeschik@pengutronix.de>
>> > Signed-off-by: Denis Osterland <Denis.Osterland@diehl.com>
>> > ---
>> >  .../rtc/{intersil,isl1208.txt => isil,isl1208.txt} |  18 +-
>> >  Documentation/hwmon/sysfs-interface                |   7 +
>> >  drivers/rtc/rtc-isl1208.c                          | 190 +++++++++++++++++++--
>> >  3 files changed, 201 insertions(+), 14 deletions(-)
>> >  rename Documentation/devicetree/bindings/rtc/{intersil,isl1208.txt => isil,isl1208.txt} (57%)
>> >
>> > diff --git a/Documentation/devicetree/bindings/rtc/intersil,isl1208.txt b/Documentation/devicetree/bindings/rtc/isil,isl1208.txt
>> > similarity index 57%
>> > rename from Documentation/devicetree/bindings/rtc/intersil,isl1208.txt
>> > rename to Documentation/devicetree/bindings/rtc/isil,isl1208.txt
>> > index a54e99feae1ca..d549699e1cfc4 100644
>> > --- a/Documentation/devicetree/bindings/rtc/intersil,isl1208.txt
>> > +++ b/Documentation/devicetree/bindings/rtc/isil,isl1208.txt
>> > @@ -1,14 +1,21 @@
>> > -Intersil ISL1208, ISL1218 I2C RTC/Alarm chip
>> > +Intersil ISL1208, ISL1218, ISL1219 I2C RTC/Alarm chip
>> >
>> >  ISL1208 is a trivial I2C device (it has simple device tree bindings,
>> >  consisting of a compatible field, an address and possibly an interrupt
>> >  line).
>> >
>> > +ISL1219 supports tamper detection user space representation through
>> > +case intrusion hwmon sensor.
>> User space and hwmon are Linux details not relevant to the binding. Just
>> describe the h/w.
> OK.
>>
>> >
>> > +ISL1219 has additional pins EVIN and #EVDET for tamper detection.
>> > +I2C devices support only one irq. #IRQ and #EVDET are open-drain active low,
>> > +so it is possible layout them to one SoC pin with pull-up.
>> > +
>> >  Required properties supported by the device:
>> >
>> >   - "compatible": must be one of
>> >     "isil,isl1208"
>> >     "isil,isl1218"
>> > +   "isil,isl1219"
>> >   - "reg": I2C bus address of the device
>> >
>> >  Optional properties:
>> > @@ -33,3 +40,12 @@ Example isl1208 node with #IRQ pin connected to SoC gpio1 pin 12:
>> >             interrupt-parent = <&gpio1>;
>> >             interrupts = <12 IRQ_TYPE_EDGE_FALLING>;
>> >     };
>> > +
>> > +Example isl1219 node with #IRQ pin and #EVDET pin connected to SoC gpio1 pin 12:
>> > +
>> > +   isl1219: isl1219@68 {
>> > +           compatible = "intersil,isl1219";
>> > +           reg = <0x68>;
>> > +           interrupts-extended = <&gpio1 12 IRQ_TYPE_EDGE_FALLING>;
>> With 2 interrupts, you should have 2 values. If they are connected
>> together, just repeat the connection. Otherwise, you can't tell if EVDET
>> is a no connect.
> If I got you right, you suggest an additional IRQ entry to parse.

Yes.

> A short example, #IRQ pin connected to gpio1 pin 12 and
> #EVDET pin connected to gpio2 pin 24:
>
> isl1219: rtc@68 {
>         compatible = "intersil,isl1219";
>         reg = <0x68>;
>         interrupt-names = "irq", "evdet";
>         interrupts-extended = <&gpio1 12 IRQ_TYPE_EDGE_FALLING>,
>                 <&gpio2 24 IRQ_TYPE_EDGE_FALLING>;
> };
>
> In driver implementation we need only one interrupt, because we can
> determinate action to take based on value of status register.

That's fine. The binding describes the hardware. Drivers can support
as much or as little as they like.

> In current implementation there was no need to do some additional
> OF parsing, everything is done by I2C generic code.
> I guess, it is not much additional work to do so, but I am not sure
> if it´s worthwhile.

If you don't care about the 2nd interrupt, I don't think you'd have to
change anything.

>>
>> There's not much point in having an example for every compatible. This
>> binding is simple enough, one should be enough.
> Shell we remove the example without an interrupt?

The existing example has a single interrupt, right? That should be
enough. You just need to document for the interrupts property which
devices have 2 interrupts and what the order is.

Rob