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

[Stefan Roese]

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>

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>

Perhaps you (or someone else) can look into this in more depth to get
to the root of this issue at a later time.

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

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