Messages in this thread | | | From | Arnd Bergmann <> | Subject | Re: [08/36] AArch64: Kernel booting and initialisation | Date | Tue, 24 Jul 2012 18:53:16 +0000 |
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On Tuesday 24 July 2012, Catalin Marinas wrote: > On Mon, Jul 23, 2012 at 09:52:22PM +0100, Christopher Covington wrote: > > Hi Catalin and Stephen, > > > > Catalin Marinas - July 8, 2012, 9:18 a.m. > > > On Fri, Jul 06, 2012 at 10:32:54PM +0100, Stephen Warren wrote: > > > > > >> Also, on Tegra at least and perhaps OMAP too, there are a few parts > > >> of earlyprintk serial port setup (i.e. port selection) which happen > > >> as part of the decompressor rather than the main kernel image, so > > >> we'd have to re-jig that too. > > > > > > Whatever we did on AArch32, if it was useful and we want to follow a > > > similar model it needs porting given that the code cannot be shared. So > > > there is nothing to re-jig but rather implement. > > > > > > As for earlyprintk, you can initialise it in the decompressed kernel > > > anyway. But even though it's a useful debugging tool, it goes against > > > the single Image aim (at least the current printascii/addruart > > > implementation). I don't have a proper implementation yet. > > > > Would DCC [1] be a reasonably commonly available early printk mechanism > > for the single image to provide? > > Yes, this can be implemented but I think it has its own restrictions, > requiring a JTAG connection.
Right, which means that it's not generic and we still need to make a decision for a how we want to solve the underlying problem. The options I see are:
1. Have no earlyprintk before loading the console drivers 2. Make the series from Domenico architecture independent code 3. Reimplement a layer like that, differently 4. Make it a compile-time option and allow this only for low level debugging purposes but disable it in distro kernels.
Arnd
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