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    SubjectRe: [08/36] AArch64: Kernel booting and initialisation
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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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