On Tuesday 28 May 2013 07:37 PM, Will Deacon wrote:
> On Tue, May 28, 2013 at 03:03:36PM +0100, Sricharan R wrote:
>> On Tuesday 28 May 2013 06:35 PM, Will Deacon wrote:
>>> On Tue, May 28, 2013 at 11:48:20AM +0100, Po-Yu Chuang wrote:
>>>> This bug was introduced in commit e651eab0.
>>>> Some v4/v5 platforms failed to boot due to this.
>>>>
>>>> Signed-off-by: Po-Yu Chuang <ratbert.chu...@gmail.com>
>>>> ---
>>>> arch/arm/mm/mmu.c | 4 +++-
>>>> 1 file changed, 3 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c
>>>> index e0d8565..19a43f8 100644
>>>> --- a/arch/arm/mm/mmu.c
>>>> +++ b/arch/arm/mm/mmu.c
>>>> @@ -620,6 +620,8 @@ static void __init map_init_section(pmd_t *pmd,
>>>> unsigned long addr,
>>>> unsigned long end, phys_addr_t phys,
>>>> const struct mem_type *type)
>>>> {
>>>> + pmd_t *p = pmd;
>>>> +
>>>> #ifndef CONFIG_ARM_LPAE
>>>> /*
>>>> * In classic MMU format, puds and pmds are folded in to
>>>> @@ -638,7 +640,7 @@ static void __init map_init_section(pmd_t *pmd,
>>>> unsigned long addr,
>>>> phys += SECTION_SIZE;
>>>> } while (pmd++, addr += SECTION_SIZE, addr != end);
>>>>
>>>> - flush_pmd_entry(pmd);
>>>> + flush_pmd_entry(p);
>>> Wait, shouldn't this flush be *inside* the loop anyway? Otherwise we just
>>> flush the cacheline containing the first pmd. The flushing code could also
>>> flush to PoU instead of PoC for UP ARMv7, but that's an unrelated
>>> optimisation.
>> I think in LPAE this loop iterates once and non LPAE twice.
>> So both the entries should be contained in same cache line right ?
> Dunno, are there any guarantees about alignment of the starting pmd? Even
> so, the function takes the range as parameters, so I don't think we
> should tailor it to the caller. It may explain why this hasn't come up
> sooner though.
>
> Will
This function is not exposed outside. And the ranges passed to this is going
to not more than 2 entries in any case. If we put the flush inside the loop,
then we will end up doing an extra flush for the same line. Regarding the
alignment, I think if the pgd base is aligned, then rest should be fine.
Will have to check this.
Regards,
Sricharan
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