On Thu, Jun 18, 2015 at 08:39:11AM +0200, Michael Lawnick wrote: > Am 17.06.2015 um 17:38 schrieb Felipe Balbi: > >Hi, > > > >On Wed, Jun 17, 2015 at 01:09:53PM +0200, Michael Lawnick wrote: > >>Am 16.06.2015 um 21:17 schrieb Felipe Balbi: > >>>With this patch we try to be as close to 50% > >>>duty cycle as possible. The reason for this > >>>is that some devices present an erratic behavior > >>>with certain duty cycles. > >>> > >>>One such example is TPS65218 PMIC which fails > >>>to change voltages when running @ 400kHz and > >>>duty cycle is lower than 34%. > >>> > >>>The idea of the patch is simple: > >>> > >>>calculate desired scl_period from requested scl > >>>and use 50% for tLow and 50% for tHigh. > >>... > >>Hmm, and what's about Philips I2C specification 2.1, Jan 2000, Table 5? > >> > >>>PARAMETER SYMBOL STANDARD-MODE FAST-MODE UNIT > >>> MIN. MAX. MIN. MAX. > >>>LOW period of the SCL clock tLOW 4.7 – 1.3 – µs > >>>HIGH period of the SCL clock tHIGH 4.0 – 0.6 – µs > >> > >>Your signal is in spec (0.85 µs high, 1,65 low). > >>Maybe your TPS65218 is just buggy or signals are bad? > > > >yes, tps is buggy, it's written in the commit log itself. > > > > So I think it is unacceptable to change the adapters code violating > specification because some buggy device doesn't work properly. read the other thread and you'll see that it's not violating jack > This change for your device has chance to blow up many correctly > working ones. How ? -- balbi
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