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

From: Jan Kiszka <jan.kiszka@siemens.com>
To: Marek Vasut <marex@denx.de>, Tom Rini <trini@konsulko.com>
Cc: U-Boot Mailing List <u-boot@lists.denx.de>,
	Hai Pham <hai.pham.ud@renesas.com>,
	Simon Goldschmidt <simon.k.r.goldschmidt@gmail.com>,
	Stephen Warren <swarren@nvidia.com>,
	Lokesh Vutla <lokeshvutla@ti.com>
Subject: Re: [PATCH] Revert "arm: bootm: Disable LMB reservation for command line and board info on arm64"
Date: Mon, 2 Aug 2021 13:36:13 +0200	[thread overview]
Message-ID: <7edb5a3f-9896-278d-fe41-e2d48bb8f974@siemens.com> (raw)
In-Reply-To: <b24ec0bd-0725-d0e5-168c-ba13d9a42c84@denx.de>

On 02.08.21 12:48, Marek Vasut wrote:
> On 8/2/21 11:37 AM, Jan Kiszka wrote:
>> On 02.08.21 02:54, 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).
>>>
>>>> This reservation is not at that spot, and a lot
>>>> more than that.
>>>
>>> Can you please elaborate on this "lot more" part ? Because as much as I
>>> studied the reservation code, the "lot more" was ATAGS on arm32 and
>>> nothing on arm64.
>>
>> See my commit log.
> 
> This is not particularly useful answer, considering the commit log says:
> "lot of crucial things", "Possibly more", "likely also on other boards"
> and other opaque statements. But really, the problem so far happens on
> one K3 board.

"Such things are the page table (tlb_addr),
relocated U-Boot and the active stack."

Jan

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