On Fri, Oct 7, 2011 at 2:02 AM, Linus Walleij <[email protected]>wrote:
> On Thu, Oct 6, 2011 at 6:35 PM, Mounir Bsaibes > <[email protected]> wrote: > > > issue: > > "Appended device trees does not work for us. Still don't know why." > > I have fixed it now, sorry for all the fuzz, appended device > trees *are* working for us, as of friday last week. > > Excellent - thank you. > Short story: we're so stupid. (As usual.) > > Long story, I *think* core problem was this: > > In kernel 3.0 you could enable CONFIG_USE_OF > and PROC_DEVICETREE to get a dummy device tree in > /proc/device-tree, so you could enable it just to get the code > compiled in. > > As of 3.1 rc:s if you enable CONFIG_USE_OF, the core > DT code will start looking for a compatible node, so you > need a .dt_compat entry in your MACHINE_START > structure, and it has to reference a matching compat node > in the device tree. Else it will print an error an hang. > > Which is fully logical, if you enable device tree, you should > use it. > > The problem was further complicated that the warning > about the missing compat node only appears in > early_printk() context since the console is not up at this > point, if you don't have that, the machine will hang without > any prints and you need to figure out what happens. > > We enabled early printk:s but since early_printk() is > problematic with multi-machine configurations we didn't > see them. > > So we were basically hit by the ambigous prossibility to > configure in earlyprints on machines with the UART in > different places, which has been discussed by Will Deacon > et al elsewhere. > > Maybe we should document in Kconfig:s > CONFIG_USE_OF option that if you enable this > for ARM your machine it won't boot unless it finds a > compatible device tree, I don't know. > copying John Ztultz to handle as he see fit. John is working on kconfig, maybe he would slip this suggestion in. > > Yours, > Linus Walleij > -- Mounir Bsaibes Project Manager Follow Linaro.org: facebook.com/pages/Linaro/155974581091106 http://twitter.com/#!/linaroorg http://www.linaro.org/linaro-blog <http://www.linaro.org/linaro-blog>
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