On 6/2/07, Johannes Stezenbach <js@xxxxxxxxxxx> wrote: > On Fri, Jun 01, 2007, Oliver Endriss wrote: > > e9hack wrote: > > > Manu Abraham wrote: > > > > e9hack wrote: > > > >> Manu Abraham wrote: > > > >>> Trent Piepho wrote: > > > >>>> What the stv0297 wants is: > > > >>>> S Addr Wr [A] Comm [A] P S Addr Rd [A] [Data] NA P > > > >>>> > > > >>> The STV0297 is just a normal demod like the others, nothing special > > > >>> about it (according to ST). Well of course i2cdump can be wrong. > > > >> The stv0297 cannot handle a repeated start condition and it needs > > > >> a little delay between the stop and the next start condition. A > > > >> stop and a start condition cannot be on the same upload command > > > >> of a saa7146 (on a TT 2300C). > > > > > > > > Any idea what the SAA7146 - STV0297 windows driver does ? > > > > > > > > > > Good point. I can monitor any access to the saa7146 registers of the > > > TT 2300C on Windows. I will check this issue. In the past, I was > > > more interested in the high level part of the i2c-communication. > > > > Any news about this? > > > > Imho Trent's patch to add I2C_M_STOP makes sense. > > > > According to the stv0299 datasheet, the stv0299 requires this STOP > > condition, too. This chip seems to be more tolerant though. > > The current driver does not send STOP before READ, and it works. > > I re-read the i2c spec (conveniently available from > http://i2c-bus.org/ ), and although it doesn't use very > clear words I think it says that any device _must_ support > repeated start conditions (e.g. section 9 FORMATS WITH 7-BIT > ADDRESSES). I just miss a few points in there.. from the URL that you pasted in. "The I2C protocol defines a so-called repeated start condition. After having sent the address byte (address and read/write bit) the master may send any number of bytes followed by a stop condition." The STV0297 requires a STOP bit in between as stated. > There's also some more explanation: > http://i2c-bus.org/RepeatedStartCondition/ > > Now, it could well be that the stv0297 i2c interface > is broken (broken because it cannot safely be used on a bus > with multiple masters), but it may also be quite possible > that the stv0297 datasheet is just inaccurate. Will any comments from STM would help ? If so, will request STM to answer some questions that we have, if any explicit ones you have, i can add them alongwith. Just that i got a bit confused now. > IMHO both possibilities are just as likely, however I trust > adq has actually tested that repeat start doesn't work. > http://linuxtv.org/hg/v4l-dvb/rev/c204a1d063aa > > Then I2C_M_STOP still makes sense, but the patch should document > that it's used only a workaround for broken hardware. > > > Regards, > Johannes Regards, Manu _______________________________________________ linux-dvb mailing list linux-dvb@xxxxxxxxxxx http://www.linuxtv.org/cgi-bin/mailman/listinfo/linux-dvb
