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

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Message-ID: <20180409211337.goavadt6f22wtkbw@earth.universe>
Date:   Mon, 9 Apr 2018 23:13:37 +0200
From:   Sebastian Reichel <sebastian.reichel@...labora.co.uk>
To:     Rob Herring <robh@...nel.org>
Cc:     Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <kernel@...gutronix.de>,
        Fabio Estevam <fabio.estevam@....com>,
        Mark Rutland <mark.rutland@....com>,
        Nandor Han <nandor.han@...com>, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org, kernel@...labora.com
Subject: Re: [PATCHv2 1/3] dt-bindings: misc: achc: Make ezport
 distinguishable

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@...labora.co.uk>
> > ---
> >  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?

&spi_controller {
    achc@...tiple {
        /* 0 = flashing interface, 1 = normal interface */
        reg = <0>, <1>;
        compatible = "ge,achc";
        reset-gpios = <&gpio42 23 ACTIVE_LOW>;
        spi-max-frequency = <42>; /* max speed for normal operation */
    };
};

-- Sebastian

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