[PATCH] Revert "arm: bootm: Disable LMB reservation for command line and board info on arm64"

[Marek Vasut]

On 8/2/21 3:00 PM, Tom Rini wrote:
> On Mon, Aug 02, 2021 at 02:54:22AM +0200, Marek Vasut wrote:
>> On 7/29/21 6:58 PM, Tom Rini wrote:
>>
>> [...]
>>
>>>>> so when did rcar3 introduce something there that shouldn't be
>>>>> reserved?  And you had phrased this to me on IRC as about reserving spot
>>>>> for ATAGS, and that not being needed of course on arm64.  But that's not
>>>>> what's going on.  Perhaps the answer is that rcar3 needs to introduce a
>>>>> board_lmb_reserve to free the normal arch one and provide whatever more
>>>>> narrow scope it needs.
>>>>
>>>> Based on the commit message 2359fa7a878 ("arm: bootm: Disable LMB
>>>> reservation for command line and board info on arm64") , this is about ATAGS
>>>> and we really don't need to reserve those on arm64.
>>>
>>> Commit 2359fa7a878 disables the entire arch_lmb_reserve function on
>>> aarch64, yes.  I assumed when we had talked that it was a small area
>>> being set aside and perhaps mis-recalled that ATAGS tended to live at
>>> DDR_BASE + 0x800 or so.
>>
>> That arch_lmb_reserve() is responsible for reserving architecture specific
>> memory. On arm32 it is ATAGS, on arm64 it is nothing as far as I can tell
>> (and see below regarding the TLB).
> 
> I don't think that LMB ever covered ATAGS.  ATAGS, I could have sworn,
> were at start of memory + 0x800 or so.  This LMB is for the top of
> memory where U-Boot is.

What is there to protect which Linux does not set up again ?