Re: [PATCH v2 2/2] ARM: mmu_32: fix setting up zero page when it is in SDRAM

[Ahmad Fatoum <a.fatoum@pengutronix.de>]

On 01.06.23 08:46, Sascha Hauer wrote:
> On Wed, May 31, 2023 at 02:40:13PM +0200, Ahmad Fatoum wrote:
>> On 31.05.23 14:38, Sascha Hauer wrote:
>>> On Wed, May 31, 2023 at 01:58:33PM +0200, Ahmad Fatoum wrote:
>>>>> From b6e5c92682467496bd9c57918996f1feffda2dd6 Mon Sep 17 00:00:00 2001
>>>>> From: Sascha Hauer <s.hauer@pengutronix.de>
>>>>> Date: Wed, 31 May 2023 11:58:51 +0200
>>>>> Subject: [PATCH] ARM: mmu_32: fix setting up zero page when it is in SDRAM
>>>>>
>>>>> We used to skip setting the zero page to faulting when SDRAM starts at
>>>>> 0x0. As bootm code now explicitly sets the zero page accessible before
>>>>> copying ATAGs there this should no longer be necessary, so
>>>>> unconditionally set the zero page to faulting during MMU startup.  This
>>>>> also moves the zero page and vector table setup after the point the
>>>>> SDRAM has been mapped cachable, because otherwise the zero page and
>>>>> possibly the vector table mapping would be overwritten.
>>>>>
>>>>> Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
>>>>> ---
>>>>>  arch/arm/cpu/mmu_32.c | 23 +++++++++--------------
>>>>>  1 file changed, 9 insertions(+), 14 deletions(-)
>>>>>
>>>>> diff --git a/arch/arm/cpu/mmu_32.c b/arch/arm/cpu/mmu_32.c
>>>>> index c4e5a3bb0a..14775768a3 100644
>>>>> --- a/arch/arm/cpu/mmu_32.c
>>>>> +++ b/arch/arm/cpu/mmu_32.c
>>>>> @@ -461,19 +461,14 @@ static int set_vector_table(unsigned long adr)
>>>>>  
>>>>>  static void create_zero_page(void)
>>>>
>>>> Is this commit incomplete? Vectors should be set up unconditionally and
>>>> create_zero_page should be called after it.
>>>
>>> Vectors are set up unconditionally and create_zero_page() is called the
>>> same way as before.
>>
>> So zero page is requested first and then on platforms with vector at
>> address 0 requesting fails and we are left without configured IVT?
> 
> I think you are misreading the patch. Please look at it again.
> create_zero_page() is called only when the vector table is not at 0x0.
> It has been like that without this patch, the patch doesn't change
> anything here.

No I get it.

Reviewed-by: Ahmad Fatoum <a.fatoum@pengutronix.de>

Thanks for bearing with me,
Ahmad

> 
> Sascha
> 

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