--- On Mon, 12/6/10, Laurent Gauch <[email protected]> wrote:
> > I don't subscribe to the idea that there is a safe, > correct and robust > > default setting for JTAG clock, The only thing that'd prevent a given board from having such a (board-specific) setting is using it with a debug adapter that doesn't support the board's preferred frequency. Trying that must trigger a fatal error from the adapter. That is: any given board/target will have such a setting, which can be saved in a config file. better to make the > user get a > > good error message Good messaging is always good. Just like Bad messaging is always bad... Somewhat tautological. But relying on messaging to achieve proper setup is not very wise. We know that users tend not to read or understand such messaging. Treat such procedures as undesirable fallbacks, except for basic error reporting. Good diagnostics (with "what to do next" advice" are so rare nowadays that I think users will run away in fear if they come across any such. > I do not say the 1MHz is safe correct and robust, but > having a known 1MHZ JTAG at startup, is is a good way to let > the user do something with openocd That presumes, wrongly, that 1 MHZ would work. First time I used OpenOCD was with a 32KHz system clock, so a 1 MHz default would have been a complete and utter lose. without having to > obligatory set a specific frequency in the script. Were it not safe/correct/robust it couldn't work. So don't even bother with it. Remember that the board's frequency only needs to be set once. Once that's done, "the user" has no more setup to handle. In fact, Whoever did the board config file should have handled all such issues, so "the user" never sees them. > THE SAFE CORRECT ROBUST frequency can never be known as > static ! See above. It's board-specific, but can very easily be "known as static" for startup. (And a good config can adapt later, to new PLL settings and so forth.) A good JTAG software has to find this frequency by > itself (auto-detecting the max safe JTAG frequency );-) All JTAGs I've used require manual config for this, since board requirements vary so much, and since detecting that a particular problem was caused by a bad frequency setting isn't very easily automated. There are a LOT of distinct failure modes, but some look like failures of a different kind (e.g. wiring errors). The best way to sort this stuff out involves ways to leverage end-user brains. (and failure modes stying simple enough that they don't need extensive troubleshooting training). _______________________________________________ Openocd-development mailing list [email protected] https://lists.berlios.de/mailman/listinfo/openocd-development
