On 29/11/14 20:47, Hartmut Knaack wrote: > Stefan Wahren schrieb am 29.11.2014 um 12:22: >>> Hartmut Knaack <knaack.h@xxxxxx> hat am 29. November 2014 um 00:28 >>> geschrieben: >>> Fabio Estevam schrieb am 19.11.2014 um 23:42: >>>> [Adding Marek] >>> Taking a closer look on how these values are used, I wondered what the real >>> value range of the registers actually are. So, anyone with access to the data >>> sheets, please confirm. >> >> the reference manual is public: >> >> http://cache.freescale.com/files/dsp/doc/ref_manual/MCIMX28RM.pdf [...] >>> For over_sample_delay, the DT bindings state a range of 1...2047. In >>> mxs_lradc_setup_ts_channel(), line 440, the value decreased by one (0...2046) >>> is written to register 0x100, bits 0-10. Question: which value range is valid >>> there? The same happens in line 498. > It's DELAY with the description: "This 11-bit field counts down to zero. At zero it triggers either a set of LRADC channel conversions or > another delay channel, or both. It can trigger up to all eight LRADCs and all four delay channels in a single > event. This counter operates on a 2KHz clock derived from crystal clock." > So, the range is 0...2047. There's also a "Note" on pages 2664-2665 of the reference manual: "The DELAY fields in HW_LRADC_DELAY0, HW_LRADC_DELAY1, HW_LRADC_DELAY2, and HW_LRADC_DELAY3 must be non-zero; otherwise, the LRADC will not trigger the delay group." So 0 isn't valid, leaving the actual range at 1..2047. >>> For settling_delay, the DT bindings state a range of 1...2047. In >>> mxs_lradc_setup_ts_channel(), line 458, that value is written to register >>> 0xf0, bits 0-10. Question: what value range is valid here, 1...2047 or >>> 0...2047? The same happens in line 517. > This is the same as register 0x100, so 0...2047 is the valid range. Yeah, 1..2047 again. Note that we subtract 1 from over_sample_delay before writing it to a register, so its DT range would be 2..2048. But we don't subtract anything from settling_delay, so its DT range would be 1..2047. Probably would be nicer to subtract 1 from neither (or both?), and have the DT ranges be the same. > Stefan, would you mind to change the DT documentation while you are on it? Kristina -- To unsubscribe from this list: send the line "unsubscribe linux-iio" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
