[PATCH] arm: mvebu: AC5/AC5X: use fixed page table size

[Stefan Roese]

On 10/20/23 10:21, Chris Packham wrote:
> 
> 
> On Fri, 20 Oct 2023, 7:18 pm Stefan Roese, <sr at denx.de 
> <mailto:sr at denx.de>> wrote:
> 
>     Hi Chris,
> 
>     On 10/18/23 22:53, Chris Packham wrote:
>      > Since commit 6cdf6b7a340d ("arm64: Use FEAT_HAFDBS to track dirty
>     pages
>      > when available") the default get_page_table_size() sets some
>     flags for
>      > more efficient handling of dirty page table entries. This causes
>      > problems on the AC5/AC5X SoC (specifically a lockup when calling
>      > __asm_switch_ttbr() via mmu_set_region_dcache_behaviour()).
>      >
>      > The reason for the lockup isn't at all clear but it can be
>     avoided if we
>      > provide our own get_page_table_size() which stops gd->arch.has_hafdbs
>      > from being set to true effectively returning the AC5/AC5X to the
>     older
>      > behaviour. This also opts for a simple fixed page table size
>     rather than
>      > trying to duplicate the more complicated logic to optimise the table
>      > size.
>      >
>      > Signed-off-by: Chris Packham <judge.packham at gmail.com
>     <mailto:judge.packham at gmail.com>>
> 
>     I'm not 100% happy with this approach / workaround - still it fixes an
>     issue on your board, so:
> 
>     Reviewed-by: Stefan Roese <sr at denx.de <mailto:sr at denx.de>>
> 
> 
> Yeah I'm not super happy about this either. But this is about the best I 
> could come up with.
> 
> 
>     Perhaps you (or someone else) can look into this in more depth to get
>     to the root of this issue at a later time.
> 
> 
> I did spend a reasonable amount of time tracking down where things were 
> going wrong, even if I couldn't figure out why. The commit message 
> basically reflects what I found.

Applied to u-boot-marvell/master

Thanks,
Stefan

> 
> 
>     Thanks,
>     Stefan
> 
>      > ---
>      >
>      >   arch/arm/mach-mvebu/alleycat5/cpu.c | 5 +++++
>      >   1 file changed, 5 insertions(+)
>      >
>      > diff --git a/arch/arm/mach-mvebu/alleycat5/cpu.c
>     b/arch/arm/mach-mvebu/alleycat5/cpu.c
>      > index 8204d9627515..7ba57ae75e76 100644
>      > --- a/arch/arm/mach-mvebu/alleycat5/cpu.c
>      > +++ b/arch/arm/mach-mvebu/alleycat5/cpu.c
>      > @@ -63,6 +63,11 @@ static struct mm_region ac5_mem_map[] = {
>      >
>      >   struct mm_region *mem_map = ac5_mem_map;
>      >
>      > +u64 get_page_table_size(void)
>      > +{
>      > +     return 0x80000;
>      > +}
>      > +
>      >   void reset_cpu(void)
>      >   {
>      >   }
> 
>     Viele Grüße,
>     Stefan Roese
> 
>     -- 
>     DENX Software Engineering GmbH,      Managing Director: Erika Unter
>     HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
>     Phone: (+49)-8142-66989-51 Fax: (+49)-8142-66989-80 Email:
>     sr at denx.de <mailto:sr at denx.de>
> 

Viele Grüße,
Stefan Roese

-- 
DENX Software Engineering GmbH,      Managing Director: Erika Unter
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-51 Fax: (+49)-8142-66989-80 Email: sr at denx.de