On Thu, Oct 24, 2013 at 06:05:53PM +0100, Manish Badarkhe wrote:

Hi Mark,

Thank you for your reply.

On Wed, Oct 23, 2013 at 10:15 PM, Mark Rutland [off-list ref] wrote:

    On Wed, Oct 23, 2013 at 05:28:52PM +0100, Manish Badarkhe wrote:
    > Add device tree based support for TI's tps6507x touchscreen.
    >
    > Signed-off-by: Manish Badarkhe [off-list ref]
    > ---
    > Changes since V3:
    >  - Rebased on top of Dmitry's changes
    >  - Removed error handling for optional DT properties
    >
    > Changes since V2:
    >  - Removed unnecessary code.
    >  - Updated Documentation to provide proper names of
    >    devicetree properties.
    >
    > Changes since V1:
    >  - Updated documentation to specify tps6507x as multifunctional
    >    device.
    >  - return proper error value in absence of platform and DT
    >    data for touchscreen.
    >  - Updated commit message.
    >
    > :100755 100755 8fffa3c... e1b9cfd... M        Documentation/devicetree/
    bindings/mfd/tps6507x.txt
    > :100644 100644 db604e0... 0cf0eb1... M        drivers/input/touchscreen/
    tps6507x-ts.c
    >  Documentation/devicetree/bindings/mfd/tps6507x.txt |   24 ++++++-
    >  drivers/input/touchscreen/tps6507x-ts.c            |   72
    ++++++++++++--------
    >  2 files changed, 67 insertions(+), 29 deletions(-)
    >
    > diff --git a/Documentation/devicetree/bindings/mfd/tps6507x.txt b/
    Documentation/devicetree/bindings/mfd/tps6507x.txt
    > index 8fffa3c..e1b9cfd 100755
    > --- a/Documentation/devicetree/bindings/mfd/tps6507x.txt
    > +++ b/Documentation/devicetree/bindings/mfd/tps6507x.txt
    > @@ -1,4 +1,8 @@
    > -TPS6507x Power Management Integrated Circuit
    > +TPS6507x Multifunctional Device.
    > +
    > +Features provided by TPS6507x:
    > +        1.Power Management Integrated Circuit.
    > +        2.Touch-Screen.
    >
    >  Required properties:
    >  - compatible: "ti,tps6507x"
    > @@ -23,6 +27,9 @@ Required properties:
    >         vindcdc1_2-supply: VDCDC1 and VDCDC2 input.
    >         vindcdc3-supply  : VDCDC3 input.
    >         vldo1_2-supply   : VLDO1 and VLDO2 input.
    > +- tsc: This node specifies touch screen data.

    This is a node, but is listed un "Required properties". That seems odd.

    When is it required?

    Why is the data under the tsc subnode? Why not directly under the main
    node?


Yes, It seems odd to add a subnode properties here. I gone through other
documentation
for MFD devices and observed that separate documentation file is present for
sub node modules.

I was trying to say that nodes != properties rather than that this should be
split into separate files.

TPS6507x is multifunctional device and having touch screen submodule. As it is
child node for
TPS6507x multifunctional device, I have created child node as "tsc".
 


    > +     ti,poll-period : Time at which touch input is getting sampled in
    ms.

    Is this for debounce? Other bindings have similar but differently named
    properties.


This is not debounce time. This time is required for input poll devices.
 

    Why is this necessary? Can the driver not choose a sane value?


poll-period is necessary to sample touch inputs. Driver will chose value
default poll
period if this value is not present. I was bit confused here, whether to add
this property
as optional or required. As with default period touch not achieve performance.
Can I make this property optional?

Please elaborate. Why will the default period be sub-optimal? What's the
tradeoff here?

 

    > +     ti,min-pressure: Minimum pressure value to trigger touch.

    What type are these? Single (u32) cells?

    What units is ti,min-pressure in?


No, its a u16 cell. It is measured in ohm. Again default value for min-pressure
is available
in driver code. Can I make this property optional?

Why is it a u16, it's very uncommon to have u16 properties.

What _physical_ units is this in, and what order of magnitude? e.g. Pascals,
millipascals.

    >
    >  Regulator Optional properties:
    >  - defdcdc_default: It's property of DCDC2 and DCDC3 regulators.
    > @@ -30,6 +37,14 @@ Regulator Optional properties:
    >                       1: If defdcdc pin of DCDC2/DCDC3 is driven HIGH.
    >    If this property is not defined, it defaults to 0 (not enabled).
    >
    > +Touchscreen Optional properties:
    > +- ti,vendor : Touchscreen vendor id to populate
    > +           in sysclass interface.
    > +- ti,product: Touchscreen product id to populate
    > +           in sysclass interface.
    > +- ti,version: Touchscreen version id to populate
    > +           in sysclass interface.

    Are these integers, strings, or something else?


These are unsigned short(u16) values.

Why?

 

    What values make sense?


These values are only to tell about chip details.

That does not describe the set of valid values.

Is ti,vendor = <4> valid? What does this mean?

Is there some standard for assignment of vendor IDs that this follows?

 

    What's the sysclass interface? That sounds like a Linux detail. The
    properties
    might be fine but the description shouldn't need to refer to Linux
    internals.


Okay, I will update description for these properties. 


    > +
    >  Example:
    >
    >       pmu: tps6507x@48 {
    > @@ -88,4 +103,11 @@ Example:
    >                       };
    >               };
    >
    > +             tsc {
    > +                     ti,poll-period = <30>;
    > +                     ti,min-pressure = <0x30>;
    > +                     ti,vendor = <0>;
    > +                     ti,product = <65070>;
    > +                     ti,version = <0x100>;
    > +             };
    >       };
    > diff --git a/drivers/input/touchscreen/tps6507x-ts.c b/drivers/input/
    touchscreen/tps6507x-ts.c
    > index db604e0..0cf0eb1 100644
    > --- a/drivers/input/touchscreen/tps6507x-ts.c
    > +++ b/drivers/input/touchscreen/tps6507x-ts.c
    > @@ -22,6 +22,8 @@
    >  #include <linux/mfd/tps6507x.h>
    >  #include <linux/input/tps6507x-ts.h>
    >  #include <linux/delay.h>
    > +#include <linux/of.h>
    > +#include <linux/of_device.h>
    >
    >  #define TSC_DEFAULT_POLL_PERIOD 30 /* ms */
    >  #define TPS_DEFAULT_MIN_PRESSURE 0x30
    > @@ -206,33 +208,54 @@ done:
    >       tps6507x_adc_standby(tsc);
    >  }
    >
    > +static void tsc_init_data(struct tps6507x_ts *tsc,
    > +             struct input_dev *input_dev)
    > +{
    > +     struct device_node *node = tsc->dev->of_node;
    > +     const struct tps6507x_board *tps_board =
    > +                     dev_get_platdata(tsc->dev);
    > +     const struct touchscreen_init_data *init_data = NULL;
    > +
    > +     if (node)
    > +             node = of_find_node_by_name(node, "tsc");

    As of_find_node_by_name traverses the list of all nodes (not just
    children),
    this may match nodes other than what you expect.


I think, It traverse nodes from parent node (i.e. tps6507x) and find child.
Please correct me if I am wrong?

No. As I said, it traverses the list of all nodes. Is there is no matching
child, it will go on and possibly match a node that is not a direct child (e.g.
a child of another node).

Perhaps of_get_child_by_name is what you want.

 


    > +     if (tps_board)
    > +             /*
    > +              * init_data points to array of touchscreen_init structure
    > +              * coming from the board-evm file.
    > +              */
    > +             init_data = tps_board->tps6507x_ts_init_data;
    > +
    > +     if (node == NULL || init_data == NULL) {
    > +             tsc->poll_dev->poll_interval = TSC_DEFAULT_POLL_PERIOD;
    > +             tsc->min_pressure = TPS_DEFAULT_MIN_PRESSURE;
    > +     } else if (init_data) {
    > +             tsc->poll_dev->poll_interval = init_data->poll_period;
    > +             tsc->min_pressure = init_data->min_pressure;
    > +             input_dev->id.vendor = init_data->vendor;
    > +             input_dev->id.product = init_data->product;
    > +             input_dev->id.version = init_data->version;
    > +     } else if (node) {
    > +             of_property_read_u32(node, "ti,poll-period",
    > +                             &tsc->poll_dev->poll_interval);
    > +             of_property_read_u16(node, "ti,min-pressure",
    > +                             &tsc->min_pressure);

    You didn't mention these were 16-bit values in the binding.

    As DTB is encoded big-endian, and you didn't use a /bits/ 16 declaration
    (making the property a u32 cell), won't this read 0 in all cases you have a
    value in the expected range (as in your example)?


I will mention these values as 16bit. values in binding.

Please explain _why_ they are 16-bit values. Even if they are 16-bit it may
make sense to have them as u32 values for general consistency and least
surprise.

Thanks,
Mark.