On 11/5/07, Scott Wood <[EMAIL PROTECTED]> wrote: > Matt Sealey wrote: > > Scott Wood wrote: > >> Jon Smirl wrote: > > > >>>>> cell-index = <1>; > >>>> What is cell-index for? > >>> I was using it to control the bus number, is that the wrong > >>> attribute? > >> > >> It shouldn't be specified at all -- the hardware has no concept of > >> a device number. > > > > Well, all i2c devices have a chip id you can probe for, > > I meant a controller device number (a.k.a. bus number), which (outside > of documentation) is purely a Linux invention, and which is what > cell-index was being used for above. > > > as for buses I think cell-index is a holdover from the way the PSC > > code is organised on the MPC5200 for example - if you have multiple > > buses which use the same registers, for example. It's redundant on > > the PSC's for programming because they all use different register > > offsets but if you move to other devices like the GPTs, then it is > > then useful for debugging (it is far more interesting to say GPT1 > > than GPT @ offset to match the)
Actually, it is not intended for this. cell-index is not intended to be able to say GPT1 instead of [EMAIL PROTECTED] (while that may be possible, it is not the intent). Nor is it a holdover from the PSC code design. It is designed to describe the internal structure of the SoC. The 5200 has 6 PSCs, and there are some chip registers which are shared between all the PSCs (for clocking, IO mode, etc). It is not sufficient to simply plop down a device tree node for each PSC because it doesn't give enough information about which bits to use in the shared regs. (For example, the port_config register) > > and in general for tweaking OTHER > > parts of the chip (for instance the CDM - very relevant!) which use > > single registers to control entire swathes of units. > > Right, that's what cell-index is for. This is different. :-) Yes, this is correct. Cheers, g. -- Grant Likely, B.Sc., P.Eng. Secret Lab Technologies Ltd. [EMAIL PROTECTED] (403) 399-0195 _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@ozlabs.org https://ozlabs.org/mailman/listinfo/linuxppc-dev