>> Not at all. The device tree describe how the hardware _is_ >> set up (after firmware, bootloader etc.); now how it _should >> be_ set up by the kernel. > > I agree with this general sentiment, but in the case of QE pin > configuration, then device tree, in a sense, does contain how the > hardware is set up. The par_io section in the device tree describes > they layout of the wiring between the SOC and peripherals. If the > par_io registers are not programmed correctly, the SOC won't be able > to communicate with the peripheral. > > Sure, the kernel currently reads the device tree and programs the > par_io registers accordingly, but that doesn't mean the information > *shouldn't* be in the device tree.
It is fine if the device tree describes how things are wired together; that's part of the device tree's purpose, after all. It is not fine if the device tree says _how to_ configure the hardware; you are supposed to put your device drivers elsewhere, not in the device tree! >> It would make a lot of sense to do this work in the firmware >> instead, but it doesn't make sense at all to put this stuff >> into the device tree. > > 1) If the firmware does configure the pins, then the device tree > *will* describe how the hardware is set up. Yes. It won't show pario register contents though. > 2) How would the firmware know how to do board configuration if it > doesn't have the instructions in the device tree? This kind of thing is typically hardcoded into the firmware (just like the device tree is) -- just put it somewhere _next to_ the device tree, not _in_ it. The device tree is not a config file for the firmware; it is an interface between the firmware and its client (an OS, typically). > Besides, every other board does it's par_io configuration based on the > device tree. So if Anton is going to break that pattern, we should be > talking about moving all that code into U-boot, instead of just > putting in a one-time exception (especially since the patch contains > no explanation as to why these par_io pins are being configured > differently than every other board). Yes, I definitely didn't mean to single out Anton's patch, sorry if it sounded that way. Segher _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@ozlabs.org https://ozlabs.org/mailman/listinfo/linuxppc-dev
