[PATCH 3/3] ARM PJ4B: Add support for errata 4611
Lior Amsalem
alior at marvell.com
Mon Jun 3 03:16:56 EDT 2013
> From: Will Deacon [mailto:will.deacon at arm.com]
> Sent: Wednesday, May 29, 2013 2:22 PM
>
> On Wed, May 29, 2013 at 11:16:58AM +0100, Gregory CLEMENT wrote:
> > From: Lior Amsalem <alior at marvell.com>
> >
> > A CP15 clean operation can result in a dead lock state if it is hit by
> > an incoming snoop event. the fiw to this issue is the following:
[Snip]
> > a/arch/arm/include/asm/tlbflush.h b/arch/arm/include/asm/tlbflush.h
> > index e3a8064..112f778 100644
> > --- a/arch/arm/include/asm/tlbflush.h
> > +++ b/arch/arm/include/asm/tlbflush.h
> > @@ -475,11 +475,22 @@ static inline void flush_pmd_entry(void *pmd) {
> > const unsigned int __tlb_flag = __cpu_tlb_flags;
> >
> > +#ifdef CONFIG_PJ4B_ERRATA_4611
> > + unsigned long flags;
> > + raw_local_irq_save(flags);
> > + dmb();
> > +#endif
> > +
> > #ifdef CONFIG_PJ4B_ERRATA_6124
> > tlb_op(TLB_DCLEAN, "c7, c14, 1 @ flush_pmd", pmd);
> > #else
> > tlb_op(TLB_DCLEAN, "c7, c10, 1 @ flush_pmd", pmd);
> > #endif
> > +
> > +#ifdef CONFIG_PJ4B_ERRATA_4611
> > + raw_local_irq_restore(flags);
> > +#endif
>
> Eeek. Why do you have to disable interrupts during this? Again, are there no
> chicken bits to save you?
It's there in order to avoid an exception that will cause the workaround (of adding a DMB)
to be dismissed.
No chicken bit for it...
>
> > tlb_l2_op(TLB_L2CLEAN_FR, "c15, c9, 1 @ L2 flush_pmd", pmd);
> >
> > if (tlb_flag(TLB_WB))
> > @@ -490,11 +501,22 @@ static inline void clean_pmd_entry(void *pmd) {
> > const unsigned int __tlb_flag = __cpu_tlb_flags;
> >
> > +#ifdef CONFIG_PJ4B_ERRATA_4611
> > + unsigned long flags;
> > + raw_local_irq_save(flags);
> > + dmb();
> > +#endif
> > +
> > #ifdef CONFIG_PJ4B_ERRATA_6124
> > tlb_op(TLB_DCLEAN, "c7, c14, 1 @ flush_pmd", pmd);
> > #else
> > tlb_op(TLB_DCLEAN, "c7, c10, 1 @ flush_pmd", pmd);
> > #endif
> > +
> > +#ifdef CONFIG_PJ4B_ERRATA_4611
> > + raw_local_irq_restore(flags);
> > +#endif
> > +
> > tlb_l2_op(TLB_L2CLEAN_FR, "c15, c9, 1 @ L2 flush_pmd", pmd); }
> >
> > diff --git a/arch/arm/mm/copypage-v6.c b/arch/arm/mm/copypage-v6.c
> > index b9bcc9d..20b69ad 100644
> > --- a/arch/arm/mm/copypage-v6.c
> > +++ b/arch/arm/mm/copypage-v6.c
> > @@ -59,11 +59,22 @@ static void
> v6_clear_user_highpage_nonaliasing(struct page *page, unsigned long
> > */
> > static void discard_old_kernel_data(void *kto) {
> > +#ifdef CONFIG_PJ4B_ERRATA_4611
> > + unsigned long flags;
> > +
> > + raw_local_irq_save(flags);
> > + dmb();
> > +#endif
> > +
> > __asm__("mcrr p15, 0, %1, %0, c6 @ 0xec401f06"
> > :
> > : "r" (kto),
> > "r" ((unsigned long)kto + PAGE_SIZE - L1_CACHE_BYTES)
> > : "cc");
> > +
> > +#ifdef CONFIG_PJ4B_ERRATA_4611
> > + raw_local_irq_restore(flags); #endif
>
> Do you actually have an aliasing vipt cache? If not, you don't care about this
> function.
No, It's a mistake, will be removed. 10x for pointing that out.
>
> > diff --git a/arch/arm/mm/proc-macros.S b/arch/arm/mm/proc-macros.S
> > index f9a0aa7..ca81291 100644
> > --- a/arch/arm/mm/proc-macros.S
> > +++ b/arch/arm/mm/proc-macros.S
> > @@ -178,7 +178,20 @@
> > #endif
> >
> > str r3, [r0]
> > +
> > +#ifdef CONFIG_PJ4B_ERRATA_4611
> > + mrs r2, cpsr
> > + orr r3, r2, #PSR_F_BIT | PSR_I_BIT
> > + msr cpsr_c, r3 @ Disable interrupts
> > + dmb @ ensure ordering with previous memory
> accesses
> > +#endif
> > +
> > mcr p15, 0, r0, c7, c10, 1 @ flush_pte
> > +
> > +#ifdef CONFIG_PJ4B_ERRATA_4611
> > + msr cpsr_c, r2 @ Restore interrupts
> > + mcr p15, 0, r0, c7, c10, 4 @ drain write buffer
> > +#endif
>
> This could be a dsb.
Yes it can.
>
> Will
Regards,
Lior Amsalem
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