On 12 December 2017 at 14:17, Peter Maydell <peter.mayd...@linaro.org> wrote: > On 12 December 2017 at 14:16, Ard Biesheuvel <ard.biesheu...@linaro.org> > wrote: >> On 12 December 2017 at 14:13, Peter Maydell <peter.mayd...@linaro.org> wrote: >>> On 12 December 2017 at 14:12, Ard Biesheuvel <ard.biesheu...@linaro.org> >>> wrote: >>>> On 12 December 2017 at 14:10, Peter Maydell <peter.mayd...@linaro.org> >>>> wrote: >>>>> That doesn't actually usefully separate debug output from the >>>>> console, though, because stdout-path is also going to point >>>>> to the UART with the lowest physical address... >>>>> >>>> >>>> By default, yes, just like is currently the case. But I would assume >>>> this new serial port could be appointed 'console' and put into >>>> stdout-path by QEMU, based on the command line options? >>> >>> We don't have any command line options for doing that, and I'm >>> generally reluctant to introduce new command line UI, especially >>> new command line UI that's specific to Arm and not also needed >>> for x86. >>> >> >> If stdout-path is always going to point to pl011@0x9000000, why would >> we need to parse it? > > If you had always parsed stdout-path, we wouldn't need to worry > about the order in which the UART nodes appear in the dtb... >
That's a fair point. But it still does not justify introducing added complexity in the firmware, if the conclusion is always going to be that the console will be on pl011@9000000. To Drew's point re DEBUG builds, I don't think we should generally enable DEBUG and send the output to nowhereland if the user does not wire it up. That's a MMIO trap and two world switches for each character written, if I am not mistaken, and the DEBUG builds are very noisy. But still, given that stdout-path is essentially written in stone anyway, could we also decide that it will always refer to pl011@9000000 by its nodename? That way, we can easily implement the early DEBUG logic by using any non-disabled non-secure PL011 that is not referenced in stdout-path, and falling back to the one that is in stdout-path, which will essentially work as it does today. And for the more elaborate DXE driver, we can find the nodename from stdout-path.
