On Wed, Sep 21, 2011 at 5:01 PM, Pawel Moll <[email protected]> wrote: > On Wed, 2011-09-21 at 15:57 +0100, Grant Likely wrote: >> On Wed, Sep 21, 2011 at 7:24 AM, Rob Herring <[email protected]> wrote: >> > On 09/21/2011 04:19 AM, Dave Martin wrote: >> >> * arm,amba-bus -- widely used by other boards and patchsets, but >> >> seems not to be documented. >> >> >> > >> > This should be dropped. There's not really any bus component to an amba >> > bus. All the probing info is within the primecell peripherals. >> >> No, if it is an AMBA bus, then it is entirely appropriate to declare >> it as an amba bus, but to also be compatible with "simple-bus". In >> fact, it would be better to use a compatible string that specifies the >> specific implementation of AMBA bus since there are several versions >> of the spec. > > Dave asked me about details of the VE implementation. It's > sort-of-complicated... ;-) > > 1. Core talks to Static Memory Controller via AMBA (AXI) > > SOC { core --AXI--> SMC } > > 2. SMC generates transaction on Static Memory Bus talking to the IO FPGA > > tile/motherboard connector { SMC --SMB--> IOFPGA } > > 3. Now, depending on the device being accessed: > > a) Transactions accessing SMSC9118, ISP1761, NOR Flash and PSRAM are > routed directly to the devices > > IOFPGA { SMB --> SMSC9118 et al. } > > b) The rest of the traffic is converted back to AMBA (AHB/APB) > transactions and sent to the devices connected to internal AMBA matrix. > > IOFPGA { SMB --> AHB/APB bus master --AHB/APB--> PL180 } > > I don't believe, though, that the DTS must reflect such level of > details. That's why I think that: > > + motherboard { > + compatible = "simple-bus"; > > and > > + peripherals@7,00000000 { > + compatible = "arm,amba-bus", "simple-bus"; > > is the best description of the reality :-)
I wonder whether an OS will ever need to know this detail. Am I right in understanding that these buses are just interconnect logic, with no OS-visible control/configuration interface? Cheers ---Dave _______________________________________________ devicetree-discuss mailing list [email protected] https://lists.ozlabs.org/listinfo/devicetree-discuss
