On Fri, Jun 07, 2024 at 10:42:51PM +0200, Caleb Connolly wrote: > Add some brief documentation on using dump_pagetables() to print out > U-Boot's pagetables during boot. > > Signed-off-by: Caleb Connolly <caleb.conno...@linaro.org> > --- > doc/arch/arm64.rst | 37 +++++++++++++++++++++++++++++++++++++ > 1 file changed, 37 insertions(+) > > diff --git a/doc/arch/arm64.rst b/doc/arch/arm64.rst > index 7c0713504c47..0c851304aad4 100644 > --- a/doc/arch/arm64.rst > +++ b/doc/arch/arm64.rst > @@ -47,8 +47,45 @@ Notes > > 6. CONFIG_ARM64 instead of CONFIG_ARMV8 is used to distinguish aarch64 and > aarch32 specific codes. > > +MMU > +--- > + > +U-Boot uses a simple page table for MMU setup. It uses the smallest number > of bits > +possible for the virtual address based on the maximum memory address (see > the logic > +in ``get_tcr()``). > + > +As with all platforms, U-Boot on ARM64 uses a 1:1 mapping of virtual to > physical addresses. > +In general, the memory map is expected to remain static once the MMU is > enabled. > + > +It is possible to debug the pagetable generated by U-Boot with the built in > +``dump_pagetable()`` and ``walk_pagetable()`` functions (the former being a > simple > +wrapper for the latter). For example the following can be added to > ``setup_all_pgtables()`` > +after the first call to ``setup_pgtables()``: > + > +.. code-block:: c > + > + dump_pagetable(gd->arch.tlb_addr, get_tcr(NULL, NULL)); > + > +This will result in a print like the following: > + > +.. code-block:: text > + > + Walking pagetable at 000000017df90000, va_bits: 36. Using 3 levels > + [0x17df91000] | Table | | > + [0x17df92000] | Table | | > + [0x000001000 - 0x000200000] | Pages | Device-nGnRnE | Non-shareable > + [0x000200000 - 0x040000000] | Block | Device-nGnRnE | Non-shareable > + [0x040000000 - 0x080000000] | Block | Device-nGnRnE | Non-shareable > + [0x080000000 - 0x140000000] | Block | Normal | > Inner-shareable > + [0x17df93000] | Table | | > + [0x140000000 - 0x17de00000] | Block | Normal | > Inner-shareable > + [0x17df94000] | Table | | > + [0x17de00000 - 0x17dfa0000] | Pages | Normal | > Inner-shareable > + > +For more information, please refer to the function documentation in > +``arch/arm/include/asm/armv8/mmu.h``.
Since the function comments are kernel-doc style, can you please rework this to leverage "kernel-doc::" and make sure it renders nicely? And this may show we should be putting some function comments in 2/3 of this series as well. -- Tom
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