Hi Rob, Le 10/09/2015 02:06, Rob Herring a écrit : > On 09/09/2015 10:45 AM, Cyrille Pitchen wrote: >> Hi Rob, >> >> Le 09/09/2015 01:40, Rob Herring a écrit : >>> On 09/01/2015 09:46 AM, Cyrille Pitchen wrote: >>>> This patch documents the DT bindings for the Atmel Flexcom which will be >>>> introduced by sama5d2x SoCs. These bindings will be used by the actual >>>> Flexcom driver to be sent in another patch. >>>> >>>> Signed-off-by: Cyrille Pitchen <cyrille.pitchen@xxxxxxxxx> >>>> Acked-by: Boris Brezillon <boris.brezillon@xxxxxxxxxxxxxxxxxx> >>>> Acked-by: Alexandre Belloni <alexandre.belloni@xxxxxxxxxxxxxxxxxx> >>> >>> A few comments, but in general looks fine. >>> >>>> --- >>>> .../devicetree/bindings/mfd/atmel-flexcom.txt | 67 ++++++++++++++++++++++ >>>> 1 file changed, 67 insertions(+) >>>> create mode 100644 Documentation/devicetree/bindings/mfd/atmel-flexcom.txt >>>> >>>> diff --git a/Documentation/devicetree/bindings/mfd/atmel-flexcom.txt b/Documentation/devicetree/bindings/mfd/atmel-flexcom.txt >>>> new file mode 100644 >>>> index 000000000000..fc3511e41542 >>>> --- /dev/null >>>> +++ b/Documentation/devicetree/bindings/mfd/atmel-flexcom.txt >>>> @@ -0,0 +1,67 @@ >>>> +* Device tree bindings for Atmel Flexcom (Flexible Serial Communication Unit) >>>> + >>>> +The Atmel Flexcom is just a wrapper which embeds a SPI controller, an I2C >>>> +controller and an USART. Only one function can be used at a time and is chosen >>>> +at boot time according to the device tree. >>> >>> Doesn't the board design choose (unless pins go to a header)? >>> >> >> The function may be chosen once for all by the board design but if we take the >> sama5d2 xplained board as an example, most Flexcoms output their pins to >> headers. >> >>>> + >>>> +Required properties: >>>> +- compatible: Should be "atmel,sama5d2-flexcom" >>>> +- reg: Should be the offset/length value for Flexcom dedicated >>>> + I/O registers (without USART, TWI or SPI registers). >>>> +- clocks: Should be the Flexcom peripheral clock from PMC. >>>> +- #address-cells: Should be <1> >>>> +- #size-cells: Should be <1> >>>> +- ranges: Should be one range for the full I/O register region >>>> + (including USART, TWI and SPI registers). >>>> +- atmel,flexcom-mode: Should be one of the 3 following macros as defined in >>>> + include/dt-bindings/mfd/atmel-flexcom.h: >>>> + - ATMEL_FLEXCOM_MODE_USART for USART >>>> + - ATMEL_FLEXCOM_MODE_SPI for SPI >>>> + - ATMEL_FLEXCOM_MODE_TWI for I2C >>>> + >>>> +Required child: >>>> +a single child device of type matching the "atmel,flexcom-mode" property. >>> >>> Okay, but why not allow all children and use "status"? >>> >> >> That is exactly what was proposed in v6 of this series: allow more than one >> child so possibly all children but only one "available" child (status = >> "okay"). >> >> The Flexocm driver still needs to find out the type of device of this >> available child to know which function is to be enabled (USART, I2C or SPI). >> So the "compatible" attribute was parsed using strstr() to search on of the >> patterns "usart", "spi" or "i2c". >> >> However the use of strstr() was discussed to know whether the driver should >> looks for a partial or an exact match of the "compatible" string. >> An exact match would require to keep the Flexcom driver synchonized with the >> 3 other drivers every time one of them introduces a new compatibility string, >> which whould have made every driver more difficult to maintain by creating a >> useless dependency. >> So this implementation relying on the "compatible" attribute was abandoned. >> >> To sum up, no other reliable (and simple) means to guess/extact the device >> type from its DT node was found so we got back to the "atmel,flexcom-mode" >> property. > > I wasn't thinking removing this property. If the mode is configured by > the bootloader, then you want to make updates to the configuration as > simple as possible. Updating atmel,flexcom-mode and status for the > children would be much more simple than creating the whole child node. > If that's not a valid usecase, then never mind. > > Rob > The Flexcom driver calls of_platform_populate(), so yes it's allowed and supported to put the 3 children in the DT as long as only one is available. Should I update the documentation to deal with optional children or leave it as it is? Best Regards, Cyrille -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
