Re: [PATCH 4/4] ARM: pbl: MMU: Make it callable multiple times

[Sascha Hauer <s.hauer@pengutronix.de>]

On Mon, Feb 23, 2026 at 09:41:23AM +0100, Ahmad Fatoum wrote:
> Hello Sascha,
> 
> On 2/23/26 9:34 AM, Sascha Hauer wrote:
> > mmu_early_enable() is called in barebox_pbl_start() after a call to
> > setup_c(). setup_c() clears the BSS which means alloc_pte() starts at
> > index zero again when mmu_early_enable() has been called earlier
> > already.
> > 
> > Some boards might want to do exactly that: Call mmu_early_enable()
> > earlier to do for example otherwise expensive hashing of xloaded
> > binaries.
> > 
> > Make mmu_early_enable() safe to be called multiple times by moving the
> > PTE index out of the BSS.
> 
> How about making setup_c() safe for calling multiple times by having it
> check and modify a variable in the .data section?

Good idea.

> 
> Would that break anything?

I don't know. We might have code that relies on exactly the current
behaviour, but I am not aware of any.

Sascha

> 
> Cheers,
> Ahmad
> 
> > 
> > Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
> > ---
> >  arch/arm/cpu/mmu_64.c | 5 ++++-
> >  1 file changed, 4 insertions(+), 1 deletion(-)
> > 
> > diff --git a/arch/arm/cpu/mmu_64.c b/arch/arm/cpu/mmu_64.c
> > index 7f38473079..2f451b3c91 100644
> > --- a/arch/arm/cpu/mmu_64.c
> > +++ b/arch/arm/cpu/mmu_64.c
> > @@ -86,7 +86,10 @@ static void set_pte_range(unsigned level, uint64_t *virt, phys_addr_t phys,
> >  #ifdef __PBL__
> >  static uint64_t *alloc_pte(void)
> >  {
> > -	static unsigned int idx;
> > +	static int idx = -1;
> > +
> > +	if (idx == -1)
> > +		idx = 0;
> >  
> >  	idx++;
> >  
> > 
> 
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> 

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