Re: [PATCHv4 4/4] ARM: versatile: support configuring versatile machine for no-MMU

[Russell King - ARM Linux <linux@armlinux.org.uk>]

On Fri, Jun 22, 2018 at 12:54:18PM -0400, Nicolas Pitre wrote:
> On Fri, 22 Jun 2018, Russell King - ARM Linux wrote:
> 
> > On Fri, Jun 22, 2018 at 12:21:33PM -0400, Nicolas Pitre wrote:
> > > On Fri, 22 Jun 2018, Russell King - ARM Linux wrote:
> > > > That is actually incorrect - you're too used to the dynamic fixup of
> > > > virt_to_phys() and friends now!
> > > > 
> > > > Given that XIP is typically used in environments where the kernel text
> > > > is very much unmodifyable, we disable CONFIG_ARM_PATCH_PHYS_VIRT.  When
> > > > disabled, we use a constant translation, based upon the build-time
> > > > CONFIG_PHYS_OFFSET and CONFIG_PAGE_OFFSET settings.
> > > > 
> > > > The early assembler relies upon these settings - which must be known
> > > > before we enable the MMU.  As such, DT parsing is not available to us
> > > > at that point (as we can't run any C code, because we won't be calling
> > > > it at the address it was linked for.)
> > > 
> > > I think you got me wrong.  I meant DT parsing at config or build time, 
> > > not at run time.
> > 
> > That seems backwards and complicated.  It seems this would end up
> > with:
> > 
> > - you configure the kernel
> > - build the dtb files
> > - reconfigure parsing a specific dtb file built in the previous step
> > - build the kernel proper
> 
> ... or just stick the right value manually when prompting for 
> XIP_PHYS_ADDR.  Really, depending on DT is a non issue that only pulls 
> the conversation away from the actual kconfig language limitation that 
> needs to be overcome.

Which is _exactly_ what we do today, so I don't see what point you're
making in this sub-thread.

I thought we were discussing about getting Kconfig to obtain settings
from dtb files.  If you have a point to make, please don't make the
discussion impossible by changing your point, it makes it a waste of
time trying to have a discussion.

-- 
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