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 -- 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
