Re: [PATCHv2 1/3] dt-bindings: misc: achc: Make ezport distinguishable

[Rob Herring]

On Mon, Apr 9, 2018 at 4:13 PM, Sebastian Reichel
<sebastian.reichel@xxxxxxxxxxxxxxx> wrote:
> Hi,
>
> On Mon, Apr 09, 2018 at 01:57:27PM -0500, Rob Herring wrote:
>> On Tue, Mar 27, 2018 at 03:52:57PM +0200, Sebastian Reichel wrote:
>> > This updates the GE ACHC binding, so that different compatible
>> > strings are used for the programming interface, which is the
>> > ezport interface from NXP MK20FN1M0VMD12 and the microcontroller's
>> > normal SPI interface.
>> >
>> > Signed-off-by: Sebastian Reichel <sebastian.reichel@xxxxxxxxxxxxxxx>
>> > ---
>> >  Documentation/devicetree/bindings/misc/ge-achc.txt | 19 ++++++++++++++++---
>> >  1 file changed, 16 insertions(+), 3 deletions(-)
>> >
>> > diff --git a/Documentation/devicetree/bindings/misc/ge-achc.txt b/Documentation/devicetree/bindings/misc/ge-achc.txt
>> > index 77df94d7a32f..6c6bd6568504 100644
>> > --- a/Documentation/devicetree/bindings/misc/ge-achc.txt
>> > +++ b/Documentation/devicetree/bindings/misc/ge-achc.txt
>> > @@ -7,7 +7,13 @@ Note: This device does not expose the peripherals as USB devices.
>> >
>> >  Required properties:
>> >
>> > -- compatible : Should be "ge,achc"
>> > +- compatible : Should be
>> > +  "ge,achc" (normal interface)
>> > +  "ge,achc-ezport" (flashing interface)
>> > +
>> > +Required properties (flashing interface only):
>> > +
>> > +- reset-gpios: GPIO Specifier for the reset GPIO
>>
>> Does the reset only affect the flashing interface and are the data pins
>> shared? If not for both, then I think the correct thing to do here is
>> just extend reg to support multiple values to represent multiple chip
>> selects.
>
> reset affects the whole chip and the same spi data/clock pins are
> being used, so extending reg should work. The flashing cannot happen
> with the same speed, though. I'm currently encoding this by using
> different "spi-max-frequency" properties. I suppose I could limit
> it in the driver instead. I tried to come up with an example for
> your suggestion. Is this what you had in mind?

If the max frequency is the device max, then that should be in the
driver. spi-max-frequency should really only be needed if the
frequency is less than the max of either the host or device.

>
> &spi_controller {
>     achc@multiple {

@0

unit addresses are the 1st address.

>         /* 0 = flashing interface, 1 = normal interface */
>         reg = <0>, <1>;

You may want to put the normal interface first as that is the primary
interface and would still work assuming the OS ignored extra entries.

>         compatible = "ge,achc";
>         reset-gpios = <&gpio42 23 ACTIVE_LOW>;
>         spi-max-frequency = <42>; /* max speed for normal operation */

42 Hz?

Rob