[PATCH v4 1/2] mach-k3: add runtime memory carveouts for MMU table

[Tom Rini]

On Sat, Jun 28, 2025 at 12:38:19AM +0530, Anshul Dalal wrote:
> On Sat Jun 28, 2025 at 12:12 AM IST, Andrew Davis wrote:
> > On 6/27/25 1:09 PM, Tom Rini wrote:
> >> On Fri, Jun 27, 2025 at 01:06:50PM -0500, Andrew Davis wrote:
> >>> On 6/18/25 7:42 AM, Anshul Dalal wrote:
> >>>> In u-boot we only provide a single MMU table for all k3 platforms,
> >>>> this does not scale for devices with reserved memory outside the range
> >>>> 0x9e780000 - 0xa0000000 or for devices with < 2GiB of memory (eg
> >>>> am62-SIP with 512MiB of RAM).
> >>>>
> >>>> To properly configure the MMU on various k3 platforms, the
> >>>> reserved-memory regions need to be queried at runtime from the
> >>>> device-tree and the MMU table should be updated accordingly.
> >>>>
> >>>> This patch adds the required fixups to the MMU table (during proper
> >>>> U-boot stage) by marking the reserved regions as non cacheable and
> >>>> keeping the remaining area as cacheable.
> >>>>
> >>>> For the A-core SPL, the 128MiB region starting from SPL_TEXT_BASE
> >>>> is marked as cacheable i.e 0x80080000 to 0x88080000.
> >>>>
> >>>> The 128MiB size is chosen to allow for future use cases such as falcon
> >>>> boot from the A-Core SPL which would require loading kernel image from
> >>>> the SPL stage. This change also ensures the reserved memory regions that
> >>>> all exist past 0x88080000 are non cacheable preventing speculative
> >>>> accesses to those addresses.
> >>>>
> >>>> Signed-off-by: Anshul Dalal <anshuld at ti.com>
> >>>> ---
> >>>> Changes for v4:
> >>>>    - Add call to k3_mem_map_init for beagleplay
> >>>>    - Mark reserved regions as non-cacheable
> >>>
> >>> In v2 I said you cannot mark any regions as non-caching. How did this
> >>> sneak back in? If the reserved memory region is marked in DT as "no-map"
> >>> it must not be mapped at all. So NAK.
> >> 
> >> Presumably at the top of your mailbox now that I just pushed it to
> >> -next. 
> >
> > Yes, this bubbled up to my attention thanks to your applied to -next message.
> >
> >> Should I revert, or expect a prompt follow-up to clean things up?
> >
> > If we get a quick cleanup patch that maps the reserved regions as caching to
> > match previous behavior that would remove much of the reason for this patch
> > in the first place. Removing mapping the reserved memory then we will break
> > remoteproc loading. Both have issues so reverting will probably be needed
> >
> 
> The idea of the patch was to carveout the optee and atf's reserved
> memory out of u-boot proper but I blindly mapped every reserved node as
> non-cacheable which was not the right approach. I can send a quick
> follow up fix but it would likely remove everything this patch added to
> begin with. So, I feel it's better to drop this altogether and I'll post
> a v5 later with the required changes.
> 
> Aplogies for any inconvenience.

OK thanks, reverting shortly.

-- 
Tom
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