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[PATCH v5 15/17] dt-bindings: qca7000: append UART interface to binding

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  [PATCH v5 15/17] dt-bindings: qca7000: append UART interface to binding Stefan Wahren <stefan.wahren@i2se.com> - 2017-05-10 11:00 +0200
    Re: [PATCH v5 15/17] dt-bindings: qca7000: append UART interface to binding Michael Heimpold <mhei@heimpold.de> - 2017-05-11 21:20 +0200
      Re: [PATCH v5 15/17] dt-bindings: qca7000: append UART interface to  binding Jakub Kicinski <kubakici@wp.pl> - 2017-05-12 04:50 +0200
        Re: [PATCH v5 15/17] dt-bindings: qca7000: append UART interface to  binding Michael Heimpold <mhei@heimpold.de> - 2017-05-12 08:20 +0200
          Re: [PATCH v5 15/17] dt-bindings: qca7000: append UART interface to  binding Jakub Kicinski <kubakici@wp.pl> - 2017-05-12 08:50 +0200
            Re: [PATCH v5 15/17] dt-bindings: qca7000: append UART interface to  binding Stefan Wahren <stefan.wahren@i2se.com> - 2017-05-19 09:20 +0200
              Re: [PATCH v5 15/17] dt-bindings: qca7000: append UART interface to binding Rob Herring <robh@kernel.org> - 2017-05-19 14:40 +0200

#1638684 — [PATCH v5 15/17] dt-bindings: qca7000: append UART interface to binding

This merges the serdev binding for the QCA7000 UART driver (Ethernet over
UART) into the existing document.

Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>
---
 .../devicetree/bindings/net/qca-qca7000.txt        | 32 ++++++++++++++++++++++
 1 file changed, 32 insertions(+)

diff --git a/Documentation/devicetree/bindings/net/qca-qca7000.txt b/Documentation/devicetree/bindings/net/qca-qca7000.txt
index a37f656..08364c3 100644
--- a/Documentation/devicetree/bindings/net/qca-qca7000.txt
+++ b/Documentation/devicetree/bindings/net/qca-qca7000.txt
@@ -54,3 +54,35 @@ ssp2: spi@80014000 {
 		local-mac-address = [ A0 B0 C0 D0 E0 F0 ];
 	};
 };
+
+(b) Ethernet over UART
+
+In order to use the QCA7000 as UART slave it must be defined as a child of a
+UART master in the device tree. It is possible to preconfigure the UART
+settings of the QCA7000 firmware, but it's not possible to change them during
+runtime.
+
+Required properties:
+- compatible        : Should be "qca,qca7000-uart"
+
+Optional properties:
+- local-mac-address : see ./ethernet.txt
+- current-speed     : current baud rate of QCA7000 which defaults to 115200
+		      if absent, see also ../serial/slave-device.txt
+
+UART Example:
+
+/* Freescale i.MX28 UART */
+auart0: serial@8006a000 {
+	compatible = "fsl,imx28-auart", "fsl,imx23-auart";
+	reg = <0x8006a000 0x2000>;
+	pinctrl-names = "default";
+	pinctrl-0 = <&auart0_2pins_a>;
+	status = "okay";
+
+	qca7000: ethernet {
+		compatible = "qca,qca7000-uart";
+		local-mac-address = [ A0 B0 C0 D0 E0 F0 ];
+		current-speed = <38400>;
+	};
+};
-- 
2.1.4

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#1639972

Hi,

Am Mittwoch, 10. Mai 2017, 10:53:26 CEST schrieb Stefan Wahren:
> This merges the serdev binding for the QCA7000 UART driver (Ethernet over
> UART) into the existing document.
> 
> Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>
> ---
>  .../devicetree/bindings/net/qca-qca7000.txt        | 32
> ++++++++++++++++++++++ 1 file changed, 32 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/net/qca-qca7000.txt
> b/Documentation/devicetree/bindings/net/qca-qca7000.txt index
> a37f656..08364c3 100644
> --- a/Documentation/devicetree/bindings/net/qca-qca7000.txt
> +++ b/Documentation/devicetree/bindings/net/qca-qca7000.txt
> @@ -54,3 +54,35 @@ ssp2: spi@80014000 {
>  		local-mac-address = [ A0 B0 C0 D0 E0 F0 ];
>  	};
>  };
> +
> +(b) Ethernet over UART
> +
> +In order to use the QCA7000 as UART slave it must be defined as a child of
> a +UART master in the device tree. It is possible to preconfigure the UART
> +settings of the QCA7000 firmware, but it's not possible to change them
> during +runtime.
> +
> +Required properties:
> +- compatible        : Should be "qca,qca7000-uart"

I already discussed this with Stefan off-list a little bit, but I would like
to bring this to a broader audience: I'm not sure whether the compatible 
should contain the "-uart" suffix, because the hardware chip is the very same
QCA7000 chip which can also be used with SPI protocol.
The only difference is the loaded firmware within the chip which can either
speak SPI or UART protocol (but not both at the same time - due to shared 
pins). So the hardware design decides which interface type is used.

At the moment, this patch series adds a dedicated driver for the UART 
protocol, in parallel to the existing SPI driver. So a different compatible
string is needed here to match against the new driver.

An alternative approach would be to re-use the existing compatible string
"qca,qca7000" for both, the SPI and UART protocol, because a "smarter" 
(combined) driver would detect which protocol to use. For example the driver 
could check for spi-cpha and/or spi-cpol which are required for SPI protocol: 
if these exists the driver could assume that SPI must be used, if both are 
missing then UART protocol should be used.
(This way it would not be necessary to check whether the node is a child of
a SPI or UART master node - but maybe this is even easier - I don't know)

Or in shorter words: my concern is that while "qca7000-uart" describes the 
hardware, it's too closely coupled to the driver implementation. Having
some feedback of the experts would be nice :-)

Thanks,
Michael

> +
> +Optional properties:
> +- local-mac-address : see ./ethernet.txt
> +- current-speed     : current baud rate of QCA7000 which defaults to 115200
> +		      if absent, see also ../serial/slave-device.txt
> +
> +UART Example:
> +
> +/* Freescale i.MX28 UART */
> +auart0: serial@8006a000 {
> +	compatible = "fsl,imx28-auart", "fsl,imx23-auart";
> +	reg = <0x8006a000 0x2000>;
> +	pinctrl-names = "default";
> +	pinctrl-0 = <&auart0_2pins_a>;
> +	status = "okay";
> +
> +	qca7000: ethernet {
> +		compatible = "qca,qca7000-uart";
> +		local-mac-address = [ A0 B0 C0 D0 E0 F0 ];
> +		current-speed = <38400>;
> +	};
> +};

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#1640143 — Re: [PATCH v5 15/17] dt-bindings: qca7000: append UART interface to binding

On Thu, 11 May 2017 21:12:22 +0200, Michael Heimpold wrote:
> Am Mittwoch, 10. Mai 2017, 10:53:26 CEST schrieb Stefan Wahren:
> > This merges the serdev binding for the QCA7000 UART driver (Ethernet over
> > UART) into the existing document.
> > 
> > Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>
> > ---
> >  .../devicetree/bindings/net/qca-qca7000.txt        | 32
> > ++++++++++++++++++++++ 1 file changed, 32 insertions(+)
> > 
> > diff --git a/Documentation/devicetree/bindings/net/qca-qca7000.txt
> > b/Documentation/devicetree/bindings/net/qca-qca7000.txt index
> > a37f656..08364c3 100644
> > --- a/Documentation/devicetree/bindings/net/qca-qca7000.txt
> > +++ b/Documentation/devicetree/bindings/net/qca-qca7000.txt
> > @@ -54,3 +54,35 @@ ssp2: spi@80014000 {
> >  		local-mac-address = [ A0 B0 C0 D0 E0 F0 ];
> >  	};
> >  };
> > +
> > +(b) Ethernet over UART
> > +
> > +In order to use the QCA7000 as UART slave it must be defined as a child of
> > a +UART master in the device tree. It is possible to preconfigure the UART
> > +settings of the QCA7000 firmware, but it's not possible to change them
> > during +runtime.
> > +
> > +Required properties:
> > +- compatible        : Should be "qca,qca7000-uart"  
> 
> I already discussed this with Stefan off-list a little bit, but I would like
> to bring this to a broader audience: I'm not sure whether the compatible 
> should contain the "-uart" suffix, because the hardware chip is the very same
> QCA7000 chip which can also be used with SPI protocol.
> The only difference is the loaded firmware within the chip which can either
> speak SPI or UART protocol (but not both at the same time - due to shared 
> pins). So the hardware design decides which interface type is used.
> 
> At the moment, this patch series adds a dedicated driver for the UART 
> protocol, in parallel to the existing SPI driver. So a different compatible
> string is needed here to match against the new driver.
> 
> An alternative approach would be to re-use the existing compatible string
> "qca,qca7000" for both, the SPI and UART protocol, because a "smarter" 
> (combined) driver would detect which protocol to use. For example the driver 
> could check for spi-cpha and/or spi-cpol which are required for SPI protocol: 
> if these exists the driver could assume that SPI must be used, if both are 
> missing then UART protocol should be used.
> (This way it would not be necessary to check whether the node is a child of
> a SPI or UART master node - but maybe this is even easier - I don't know)
> 
> Or in shorter words: my concern is that while "qca7000-uart" describes the 
> hardware, it's too closely coupled to the driver implementation. Having
> some feedback of the experts would be nice :-)

I'm no expert, but devices which can do both I2C and SPI are quite
common, and they usually have the same compatible string for both
buses.

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#1640222 — Re: [PATCH v5 15/17] dt-bindings: qca7000: append UART interface to binding

Hi,

Zitat von Jakub Kicinski <kubakici@wp.pl>:

> On Thu, 11 May 2017 21:12:22 +0200, Michael Heimpold wrote:
>> Am Mittwoch, 10. Mai 2017, 10:53:26 CEST schrieb Stefan Wahren:
>> > This merges the serdev binding for the QCA7000 UART driver (Ethernet over
>> > UART) into the existing document.
>> >
>> > Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>
>> > ---
>> >  .../devicetree/bindings/net/qca-qca7000.txt        | 32
>> > ++++++++++++++++++++++ 1 file changed, 32 insertions(+)
>> >
>> > diff --git a/Documentation/devicetree/bindings/net/qca-qca7000.txt
>> > b/Documentation/devicetree/bindings/net/qca-qca7000.txt index
>> > a37f656..08364c3 100644
>> > --- a/Documentation/devicetree/bindings/net/qca-qca7000.txt
>> > +++ b/Documentation/devicetree/bindings/net/qca-qca7000.txt
>> > @@ -54,3 +54,35 @@ ssp2: spi@80014000 {
>> >  		local-mac-address = [ A0 B0 C0 D0 E0 F0 ];
>> >  	};
>> >  };
>> > +
>> > +(b) Ethernet over UART
>> > +
>> > +In order to use the QCA7000 as UART slave it must be defined as  
>> a child of
>> > a +UART master in the device tree. It is possible to preconfigure the UART
>> > +settings of the QCA7000 firmware, but it's not possible to change them
>> > during +runtime.
>> > +
>> > +Required properties:
>> > +- compatible        : Should be "qca,qca7000-uart"
>>
>> I already discussed this with Stefan off-list a little bit, but I would like
>> to bring this to a broader audience: I'm not sure whether the compatible
>> should contain the "-uart" suffix, because the hardware chip is the  
>> very same
>> QCA7000 chip which can also be used with SPI protocol.
>> The only difference is the loaded firmware within the chip which can either
>> speak SPI or UART protocol (but not both at the same time - due to shared
>> pins). So the hardware design decides which interface type is used.
>>
>> At the moment, this patch series adds a dedicated driver for the UART
>> protocol, in parallel to the existing SPI driver. So a different compatible
>> string is needed here to match against the new driver.
>>
>> An alternative approach would be to re-use the existing compatible string
>> "qca,qca7000" for both, the SPI and UART protocol, because a "smarter"
>> (combined) driver would detect which protocol to use. For example the driver
>> could check for spi-cpha and/or spi-cpol which are required for SPI  
>> protocol:
>> if these exists the driver could assume that SPI must be used, if both are
>> missing then UART protocol should be used.
>> (This way it would not be necessary to check whether the node is a child of
>> a SPI or UART master node - but maybe this is even easier - I don't know)
>>
>> Or in shorter words: my concern is that while "qca7000-uart" describes the
>> hardware, it's too closely coupled to the driver implementation. Having
>> some feedback of the experts would be nice :-)
>
> I'm no expert, but devices which can do both I2C and SPI are quite
> common, and they usually have the same compatible string for both
> buses.

do you have an example driver at hand? I only found GPIO mcp23s08 driver,
which can handle both I2C and SPI chips, but there are different compatible
strings used to distinguish several chip models.

Regards,
Michael

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#1640228 — Re: [PATCH v5 15/17] dt-bindings: qca7000: append UART interface to binding

On Fri, 12 May 2017 06:15:52 +0000, Michael Heimpold wrote:
> Hi,
> 
> Zitat von Jakub Kicinski <kubakici@wp.pl>:
> 
> > On Thu, 11 May 2017 21:12:22 +0200, Michael Heimpold wrote:  
> >> Am Mittwoch, 10. Mai 2017, 10:53:26 CEST schrieb Stefan Wahren:  
> >> > This merges the serdev binding for the QCA7000 UART driver (Ethernet over
> >> > UART) into the existing document.
> >> >
> >> > Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>
> >> > ---
> >> >  .../devicetree/bindings/net/qca-qca7000.txt        | 32
> >> > ++++++++++++++++++++++ 1 file changed, 32 insertions(+)
> >> >
> >> > diff --git a/Documentation/devicetree/bindings/net/qca-qca7000.txt
> >> > b/Documentation/devicetree/bindings/net/qca-qca7000.txt index
> >> > a37f656..08364c3 100644
> >> > --- a/Documentation/devicetree/bindings/net/qca-qca7000.txt
> >> > +++ b/Documentation/devicetree/bindings/net/qca-qca7000.txt
> >> > @@ -54,3 +54,35 @@ ssp2: spi@80014000 {
> >> >  		local-mac-address = [ A0 B0 C0 D0 E0 F0 ];
> >> >  	};
> >> >  };
> >> > +
> >> > +(b) Ethernet over UART
> >> > +
> >> > +In order to use the QCA7000 as UART slave it must be defined as    
> >> a child of  
> >> > a +UART master in the device tree. It is possible to preconfigure the UART
> >> > +settings of the QCA7000 firmware, but it's not possible to change them
> >> > during +runtime.
> >> > +
> >> > +Required properties:
> >> > +- compatible        : Should be "qca,qca7000-uart"  
> >>
> >> I already discussed this with Stefan off-list a little bit, but I would like
> >> to bring this to a broader audience: I'm not sure whether the compatible
> >> should contain the "-uart" suffix, because the hardware chip is the  
> >> very same
> >> QCA7000 chip which can also be used with SPI protocol.
> >> The only difference is the loaded firmware within the chip which can either
> >> speak SPI or UART protocol (but not both at the same time - due to shared
> >> pins). So the hardware design decides which interface type is used.
> >>
> >> At the moment, this patch series adds a dedicated driver for the UART
> >> protocol, in parallel to the existing SPI driver. So a different compatible
> >> string is needed here to match against the new driver.
> >>
> >> An alternative approach would be to re-use the existing compatible string
> >> "qca,qca7000" for both, the SPI and UART protocol, because a "smarter"
> >> (combined) driver would detect which protocol to use. For example the driver
> >> could check for spi-cpha and/or spi-cpol which are required for SPI  
> >> protocol:
> >> if these exists the driver could assume that SPI must be used, if both are
> >> missing then UART protocol should be used.
> >> (This way it would not be necessary to check whether the node is a child of
> >> a SPI or UART master node - but maybe this is even easier - I don't know)
> >>
> >> Or in shorter words: my concern is that while "qca7000-uart" describes the
> >> hardware, it's too closely coupled to the driver implementation. Having
> >> some feedback of the experts would be nice :-)  
> >
> > I'm no expert, but devices which can do both I2C and SPI are quite
> > common, and they usually have the same compatible string for both
> > buses.  
> 
> do you have an example driver at hand? I only found GPIO mcp23s08 driver,
> which can handle both I2C and SPI chips, but there are different compatible
> strings used to distinguish several chip models.

I think drivers/tty/serial/sc16is7xx.c has the same strings, and some
Kconfig magic to work when either bus is enabled in .config.

Quick grep shows there are couple more potential ones to look at:

$ find . -name Kconfig | xargs grep -n 'SPI_MASTER.* I2C' 
./drivers/tty/serial/Kconfig:1208:        depends on (SPI_MASTER && !I2C) || I2C
./drivers/mfd/Kconfig:327:	depends on (SPI_MASTER || I2C)
./drivers/iio/dac/Kconfig:10:	depends on (SPI_MASTER && I2C!=m) || I2C
./drivers/iio/dac/Kconfig:34:	depends on (SPI_MASTER && I2C!=m) || I2C
./drivers/iio/dac/Kconfig:57:	depends on (SPI_MASTER && I2C!=m) || I2C
./drivers/gpio/Kconfig:1231:	depends on (SPI_MASTER && !I2C) || I2C
$ find . -name Kconfig | xargs grep -n 'I2C.*||.*SPI_MASTER' 
./drivers/mfd/Kconfig:1094:	depends on (I2C=y || SPI_MASTER=y)
./drivers/iio/gyro/Kconfig:55:	depends on (I2C || SPI_MASTER)
./drivers/iio/gyro/Kconfig:107:	depends on (I2C || SPI_MASTER) && SYSFS
./drivers/iio/accel/Kconfig:153:	depends on (I2C || SPI_MASTER) && SYSFS
./drivers/iio/pressure/Kconfig:20:	depends on (I2C || SPI_MASTER)
./drivers/iio/pressure/Kconfig:161:	depends on (I2C || SPI_MASTER) && SYSFS
./drivers/iio/magnetometer/Kconfig:118:	depends on (I2C || SPI_MASTER) && SYSFS

drivers/mfd/mc13xxx-*.c seems to have the same strings.  The iio/dac drivers
don't support DT but do share names.  The MCP GPIO chip you mention indeed has
different product names based on the bus it's made for (0 vs s in the middle 
of the name), so I gather less relevant case?  drivers/iio/pressure/bmp280-*.c 
has the same strings, if I'm looking correctly... I didn't look at the others.

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#1645262 — Re: [PATCH v5 15/17] dt-bindings: qca7000: append UART interface to binding

Hi Rob,

Am 12.05.2017 um 08:43 schrieb Jakub Kicinski:
> On Fri, 12 May 2017 06:15:52 +0000, Michael Heimpold wrote:
>> Hi,
>>
>> Zitat von Jakub Kicinski <kubakici@wp.pl>:
>>
>>> On Thu, 11 May 2017 21:12:22 +0200, Michael Heimpold wrote:  
>>>> Am Mittwoch, 10. Mai 2017, 10:53:26 CEST schrieb Stefan Wahren:  
>>>>> This merges the serdev binding for the QCA7000 UART driver (Ethernet over
>>>>> UART) into the existing document.
>>>>>
>>>>> Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>
>>>>> ---
>>>>>  .../devicetree/bindings/net/qca-qca7000.txt        | 32
>>>>> ++++++++++++++++++++++ 1 file changed, 32 insertions(+)
>>>>>
>>>>> diff --git a/Documentation/devicetree/bindings/net/qca-qca7000.txt
>>>>> b/Documentation/devicetree/bindings/net/qca-qca7000.txt index
>>>>> a37f656..08364c3 100644
>>>>> --- a/Documentation/devicetree/bindings/net/qca-qca7000.txt
>>>>> +++ b/Documentation/devicetree/bindings/net/qca-qca7000.txt
>>>>> @@ -54,3 +54,35 @@ ssp2: spi@80014000 {
>>>>>  		local-mac-address = [ A0 B0 C0 D0 E0 F0 ];
>>>>>  	};
>>>>>  };
>>>>> +
>>>>> +(b) Ethernet over UART
>>>>> +
>>>>> +In order to use the QCA7000 as UART slave it must be defined as    
>>>> a child of  
>>>>> a +UART master in the device tree. It is possible to preconfigure the UART
>>>>> +settings of the QCA7000 firmware, but it's not possible to change them
>>>>> during +runtime.
>>>>> +
>>>>> +Required properties:
>>>>> +- compatible        : Should be "qca,qca7000-uart"  
>>>> I already discussed this with Stefan off-list a little bit, but I would like
>>>> to bring this to a broader audience: I'm not sure whether the compatible
>>>> should contain the "-uart" suffix, because the hardware chip is the  
>>>> very same
>>>> QCA7000 chip which can also be used with SPI protocol.
>>>> The only difference is the loaded firmware within the chip which can either
>>>> speak SPI or UART protocol (but not both at the same time - due to shared
>>>> pins). So the hardware design decides which interface type is used.
>>>>
>>>> At the moment, this patch series adds a dedicated driver for the UART
>>>> protocol, in parallel to the existing SPI driver. So a different compatible
>>>> string is needed here to match against the new driver.
>>>>
>>>> An alternative approach would be to re-use the existing compatible string
>>>> "qca,qca7000" for both, the SPI and UART protocol, because a "smarter"
>>>> (combined) driver would detect which protocol to use. For example the driver
>>>> could check for spi-cpha and/or spi-cpol which are required for SPI  
>>>> protocol:
>>>> if these exists the driver could assume that SPI must be used, if both are
>>>> missing then UART protocol should be used.
>>>> (This way it would not be necessary to check whether the node is a child of
>>>> a SPI or UART master node - but maybe this is even easier - I don't know)
>>>>
>>>> Or in shorter words: my concern is that while "qca7000-uart" describes the
>>>> hardware, it's too closely coupled to the driver implementation. Having
>>>> some feedback of the experts would be nice :-)  
>>> I'm no expert, but devices which can do both I2C and SPI are quite
>>> common, and they usually have the same compatible string for both
>>> buses.  
>> do you have an example driver at hand? I only found GPIO mcp23s08 driver,
>> which can handle both I2C and SPI chips, but there are different compatible
>> strings used to distinguish several chip models.
> I think drivers/tty/serial/sc16is7xx.c has the same strings, and some
> Kconfig magic to work when either bus is enabled in .config.
>
> Quick grep shows there are couple more potential ones to look at:
>
> $ find . -name Kconfig | xargs grep -n 'SPI_MASTER.* I2C' 
> ./drivers/tty/serial/Kconfig:1208:        depends on (SPI_MASTER && !I2C) || I2C
> ./drivers/mfd/Kconfig:327:	depends on (SPI_MASTER || I2C)
> ./drivers/iio/dac/Kconfig:10:	depends on (SPI_MASTER && I2C!=m) || I2C
> ./drivers/iio/dac/Kconfig:34:	depends on (SPI_MASTER && I2C!=m) || I2C
> ./drivers/iio/dac/Kconfig:57:	depends on (SPI_MASTER && I2C!=m) || I2C
> ./drivers/gpio/Kconfig:1231:	depends on (SPI_MASTER && !I2C) || I2C
> $ find . -name Kconfig | xargs grep -n 'I2C.*||.*SPI_MASTER' 
> ./drivers/mfd/Kconfig:1094:	depends on (I2C=y || SPI_MASTER=y)
> ./drivers/iio/gyro/Kconfig:55:	depends on (I2C || SPI_MASTER)
> ./drivers/iio/gyro/Kconfig:107:	depends on (I2C || SPI_MASTER) && SYSFS
> ./drivers/iio/accel/Kconfig:153:	depends on (I2C || SPI_MASTER) && SYSFS
> ./drivers/iio/pressure/Kconfig:20:	depends on (I2C || SPI_MASTER)
> ./drivers/iio/pressure/Kconfig:161:	depends on (I2C || SPI_MASTER) && SYSFS
> ./drivers/iio/magnetometer/Kconfig:118:	depends on (I2C || SPI_MASTER) && SYSFS
>
> drivers/mfd/mc13xxx-*.c seems to have the same strings.  The iio/dac drivers
> don't support DT but do share names.  The MCP GPIO chip you mention indeed has
> different product names based on the bus it's made for (0 vs s in the middle 
> of the name), so I gather less relevant case?  drivers/iio/pressure/bmp280-*.c 
> has the same strings, if I'm looking correctly... I didn't look at the others.

are you okay with the suggestion to use the compatible "qca,qca7000" for
both drivers?

Should we mark "qca,qca7000-spi" as deprecated?

Regards
Stefan

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#1645565

On Fri, May 19, 2017 at 2:13 AM, Stefan Wahren <stefan.wahren@i2se.com> wrote:
> Hi Rob,
>
> Am 12.05.2017 um 08:43 schrieb Jakub Kicinski:
>> On Fri, 12 May 2017 06:15:52 +0000, Michael Heimpold wrote:
>>> Hi,
>>>
>>> Zitat von Jakub Kicinski <kubakici@wp.pl>:
>>>
>>>> On Thu, 11 May 2017 21:12:22 +0200, Michael Heimpold wrote:
>>>>> Am Mittwoch, 10. Mai 2017, 10:53:26 CEST schrieb Stefan Wahren:
>>>>>> This merges the serdev binding for the QCA7000 UART driver (Ethernet over
>>>>>> UART) into the existing document.
>>>>>>
>>>>>> Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>
>>>>>> ---
>>>>>>  .../devicetree/bindings/net/qca-qca7000.txt        | 32
>>>>>> ++++++++++++++++++++++ 1 file changed, 32 insertions(+)
>>>>>>
>>>>>> diff --git a/Documentation/devicetree/bindings/net/qca-qca7000.txt
>>>>>> b/Documentation/devicetree/bindings/net/qca-qca7000.txt index
>>>>>> a37f656..08364c3 100644
>>>>>> --- a/Documentation/devicetree/bindings/net/qca-qca7000.txt
>>>>>> +++ b/Documentation/devicetree/bindings/net/qca-qca7000.txt
>>>>>> @@ -54,3 +54,35 @@ ssp2: spi@80014000 {
>>>>>>           local-mac-address = [ A0 B0 C0 D0 E0 F0 ];
>>>>>>   };
>>>>>>  };
>>>>>> +
>>>>>> +(b) Ethernet over UART
>>>>>> +
>>>>>> +In order to use the QCA7000 as UART slave it must be defined as
>>>>> a child of
>>>>>> a +UART master in the device tree. It is possible to preconfigure the UART
>>>>>> +settings of the QCA7000 firmware, but it's not possible to change them
>>>>>> during +runtime.
>>>>>> +
>>>>>> +Required properties:
>>>>>> +- compatible        : Should be "qca,qca7000-uart"
>>>>> I already discussed this with Stefan off-list a little bit, but I would like
>>>>> to bring this to a broader audience: I'm not sure whether the compatible
>>>>> should contain the "-uart" suffix, because the hardware chip is the
>>>>> very same
>>>>> QCA7000 chip which can also be used with SPI protocol.
>>>>> The only difference is the loaded firmware within the chip which can either
>>>>> speak SPI or UART protocol (but not both at the same time - due to shared
>>>>> pins). So the hardware design decides which interface type is used.
>>>>>
>>>>> At the moment, this patch series adds a dedicated driver for the UART
>>>>> protocol, in parallel to the existing SPI driver. So a different compatible
>>>>> string is needed here to match against the new driver.
>>>>>
>>>>> An alternative approach would be to re-use the existing compatible string
>>>>> "qca,qca7000" for both, the SPI and UART protocol, because a "smarter"
>>>>> (combined) driver would detect which protocol to use. For example the driver
>>>>> could check for spi-cpha and/or spi-cpol which are required for SPI
>>>>> protocol:
>>>>> if these exists the driver could assume that SPI must be used, if both are
>>>>> missing then UART protocol should be used.
>>>>> (This way it would not be necessary to check whether the node is a child of
>>>>> a SPI or UART master node - but maybe this is even easier - I don't know)
>>>>>
>>>>> Or in shorter words: my concern is that while "qca7000-uart" describes the
>>>>> hardware, it's too closely coupled to the driver implementation. Having
>>>>> some feedback of the experts would be nice :-)
>>>> I'm no expert, but devices which can do both I2C and SPI are quite
>>>> common, and they usually have the same compatible string for both
>>>> buses.
>>> do you have an example driver at hand? I only found GPIO mcp23s08 driver,
>>> which can handle both I2C and SPI chips, but there are different compatible
>>> strings used to distinguish several chip models.
>> I think drivers/tty/serial/sc16is7xx.c has the same strings, and some
>> Kconfig magic to work when either bus is enabled in .config.
>>
>> Quick grep shows there are couple more potential ones to look at:
>>
>> $ find . -name Kconfig | xargs grep -n 'SPI_MASTER.* I2C'
>> ./drivers/tty/serial/Kconfig:1208:        depends on (SPI_MASTER && !I2C) || I2C
>> ./drivers/mfd/Kconfig:327:    depends on (SPI_MASTER || I2C)
>> ./drivers/iio/dac/Kconfig:10: depends on (SPI_MASTER && I2C!=m) || I2C
>> ./drivers/iio/dac/Kconfig:34: depends on (SPI_MASTER && I2C!=m) || I2C
>> ./drivers/iio/dac/Kconfig:57: depends on (SPI_MASTER && I2C!=m) || I2C
>> ./drivers/gpio/Kconfig:1231:  depends on (SPI_MASTER && !I2C) || I2C
>> $ find . -name Kconfig | xargs grep -n 'I2C.*||.*SPI_MASTER'
>> ./drivers/mfd/Kconfig:1094:   depends on (I2C=y || SPI_MASTER=y)
>> ./drivers/iio/gyro/Kconfig:55:        depends on (I2C || SPI_MASTER)
>> ./drivers/iio/gyro/Kconfig:107:       depends on (I2C || SPI_MASTER) && SYSFS
>> ./drivers/iio/accel/Kconfig:153:      depends on (I2C || SPI_MASTER) && SYSFS
>> ./drivers/iio/pressure/Kconfig:20:    depends on (I2C || SPI_MASTER)
>> ./drivers/iio/pressure/Kconfig:161:   depends on (I2C || SPI_MASTER) && SYSFS
>> ./drivers/iio/magnetometer/Kconfig:118:       depends on (I2C || SPI_MASTER) && SYSFS
>>
>> drivers/mfd/mc13xxx-*.c seems to have the same strings.  The iio/dac drivers
>> don't support DT but do share names.  The MCP GPIO chip you mention indeed has
>> different product names based on the bus it's made for (0 vs s in the middle
>> of the name), so I gather less relevant case?  drivers/iio/pressure/bmp280-*.c
>> has the same strings, if I'm looking correctly... I didn't look at the others.
>
> are you okay with the suggestion to use the compatible "qca,qca7000" for
> both drivers?

I believe I said I was fine either way.

> Should we mark "qca,qca7000-spi" as deprecated?

Yes.

Rob

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