Hi, Tomasz 2013/8/31 Tomasz Figa <tomasz.figa@xxxxxxxxx>: > Hi, > > [Ccing DT binding maintainers] > > On Tuesday 27 of August 2013 08:50:03 wangyuhang wrote: >> Add spi-tmax-nbits and spi-rmax-nbits for spi slave node. >> Modify the related dt document(spi-bus.txt) >> spi-tmax-nbits:Max number of bits slave will use for MOSI(writting) >> spi-rmax-nbits:Max number of bits slave will use for MISO(reading) >> Support for spi-tx/rmax-nbits in SPI framework has been picked[1]. >> [1]: http://comments.gmane.org/gmane.linux.kernel.spi.devel/14420 >> Commit Id:f477b7fb13df2b843997559ff34e87d054ba6538 >> >> Signed-off-by: wangyuhang <wangyuhang2014@xxxxxxxxx> >> --- >> Documentation/devicetree/bindings/spi/spi-bus.txt | 16 >> ++++++++++++++++ 1 file changed, 16 insertions(+) >> >> diff --git a/Documentation/devicetree/bindings/spi/spi-bus.txt >> b/Documentation/devicetree/bindings/spi/spi-bus.txt index >> 296015e..211336c 100644 >> --- a/Documentation/devicetree/bindings/spi/spi-bus.txt >> +++ b/Documentation/devicetree/bindings/spi/spi-bus.txt >> @@ -55,6 +55,22 @@ contain the following properties. >> chip select active high >> - spi-3wire - (optional) Empty property indicating device >> requires 3-wire mode. >> +- spi-tmax-nbits - (optional) Max number of bits slave will use for >> + MOSI(writting) >> +- spi-rmax-nbits - (optional) Max number of bits slave will use for >> + MISO(reading) > > May I ask for more human-readable names, please? > > If we look around, there are already devices using bus-width property, so > for consistency we could use tx-bus-width and rx-bus-width here or even a > single bus-width property taking two cells, first tx and second rx? > Yes, you are right. bus_width is really more widely used. So I will correct it. > Let's hear others' opinion on this as well. > > Also the properties should be telling information about hardware, so > probably in this case the meaning would be the number of wires that are > physically wired on the board. > >> + > > One or two sentences about what this dual/quad thing is about would be > nice here, e.g. > > Some SPI controllers and devices support Dual and/or Quad SPI > mode, which is [...]. It allows [...], etc. > OK, Thanks. >> +So if for example the slave has 4 wires for writting and 2 wires for >> reading, +and the spi-tx/rx-nbits property should be set as follows: >> + >> +spi-tmax-nbits = <4>; >> +spi-rmax-nbits = <2>; >> + >> +Now the value that spi-tmax-nbits and spi-rmax-nbits can receive is >> only +1(single), 2(dual) and 4(quad). If you don't set spi-tmax-nbits >> or spi-rmax-nbits, +spi_device mode will be set in single(1 wire) as >> default. Another point, if +property:spi-3wire is set, spi-t/rmax-nbits >> is forbidden to set to <2 or 4>, +otherwise, an errro will return. > > typo: errro > > Also an error or "returning an error" is an OS specific term. This > statement should rather be something along > > Dual/Quad mode is not allowed when 3-wire mode is used. > Got it, Thanks a lot. -- 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
