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Re: [PATCH] MIPS: tlb-r4k: panic if the MMU doesn't support PAGE_SIZE

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  Re: [PATCH] MIPS: tlb-r4k: panic if the MMU doesn't support PAGE_SIZE Paul Burton <paul.burton@imgtec.com> - 2016-02-10 23:20 +0100
    Re: [PATCH] MIPS: tlb-r4k: panic if the MMU doesn't support  PAGE_SIZE "Maciej W. Rozycki" <macro@imgtec.com> - 2016-02-11 20:40 +0100
      Re: [PATCH] MIPS: tlb-r4k: panic if the MMU doesn't support PAGE_SIZE Ralf Baechle <ralf@linux-mips.org> - 2016-02-12 12:00 +0100
    Re: [PATCH] MIPS: tlb-r4k: panic if the MMU doesn't support PAGE_SIZE Ralf Baechle <ralf@linux-mips.org> - 2016-02-12 17:40 +0100

#1331541 — Re: [PATCH] MIPS: tlb-r4k: panic if the MMU doesn't support PAGE_SIZE

On Mon, Jul 13, 2015 at 05:12:44PM +0100, Paul Burton wrote:
> After writing the appropriate mask to the cop0 PageMask register, read
> the register back & check it matches what we want. If it doesn't then
> the MMU does not support the page size the kernel is configured for and
> we're better off bailing than continuing to do odd things with TLB
> exceptions.
> 
> Signed-off-by: Paul Burton <paul.burton@imgtec.com>
> ---

Hi Ralf,

This patch is marked as accepted in patchwork[1] but is not present in
upstream. Did you lose it somehow? Could you please merge it?

Thanks,
    Paul

[1] http://patchwork.linux-mips.org/patch/10691/

>  arch/mips/mm/tlb-r4k.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/arch/mips/mm/tlb-r4k.c b/arch/mips/mm/tlb-r4k.c
> index 08318ec..4330315 100644
> --- a/arch/mips/mm/tlb-r4k.c
> +++ b/arch/mips/mm/tlb-r4k.c
> @@ -19,6 +19,7 @@
>  #include <asm/cpu.h>
>  #include <asm/cpu-type.h>
>  #include <asm/bootinfo.h>
> +#include <asm/hazards.h>
>  #include <asm/mmu_context.h>
>  #include <asm/pgtable.h>
>  #include <asm/tlb.h>
> @@ -486,6 +487,10 @@ static void r4k_tlb_configure(void)
>  	 *     be set to fixed-size pages.
>  	 */
>  	write_c0_pagemask(PM_DEFAULT_MASK);
> +	back_to_back_c0_hazard();
> +	if (read_c0_pagemask() != PM_DEFAULT_MASK)
> +		panic("MMU doesn't support PAGE_SIZE=0x%lx", PAGE_SIZE);
> +
>  	write_c0_wired(0);
>  	if (current_cpu_type() == CPU_R10000 ||
>  	    current_cpu_type() == CPU_R12000 ||
> -- 
> 2.4.5
> 

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#1332334 — Re: [PATCH] MIPS: tlb-r4k: panic if the MMU doesn't support PAGE_SIZE

On Wed, 10 Feb 2016, Paul Burton wrote:

> > diff --git a/arch/mips/mm/tlb-r4k.c b/arch/mips/mm/tlb-r4k.c
> > index 08318ec..4330315 100644
> > --- a/arch/mips/mm/tlb-r4k.c
> > +++ b/arch/mips/mm/tlb-r4k.c
> > @@ -486,6 +487,10 @@ static void r4k_tlb_configure(void)
> >  	 *     be set to fixed-size pages.
> >  	 */
> >  	write_c0_pagemask(PM_DEFAULT_MASK);
> > +	back_to_back_c0_hazard();
> > +	if (read_c0_pagemask() != PM_DEFAULT_MASK)
> > +		panic("MMU doesn't support PAGE_SIZE=0x%lx", PAGE_SIZE);

 I think it would make sense to report here what the minimum/maximum page 
size actually supported is, so that the users know what there might be 
after.

  Maciej

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#1332672

On Thu, Feb 11, 2016 at 07:37:12PM +0000, Maciej W. Rozycki wrote:

> > > index 08318ec..4330315 100644
> > > --- a/arch/mips/mm/tlb-r4k.c
> > > +++ b/arch/mips/mm/tlb-r4k.c
> > > @@ -486,6 +487,10 @@ static void r4k_tlb_configure(void)
> > >  	 *     be set to fixed-size pages.
> > >  	 */
> > >  	write_c0_pagemask(PM_DEFAULT_MASK);
> > > +	back_to_back_c0_hazard();
> > > +	if (read_c0_pagemask() != PM_DEFAULT_MASK)
> > > +		panic("MMU doesn't support PAGE_SIZE=0x%lx", PAGE_SIZE);
> 
>  I think it would make sense to report here what the minimum/maximum page 
> size actually supported is, so that the users know what there might be 
> after.

This is a very unlikely error condition to be hit so I'd rather keep it
simple.  Even just BUG_ON() would suffice.

  Ralf

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#1332879

On Wed, Feb 10, 2016 at 02:10:49PM -0800, Paul Burton wrote:

> On Mon, Jul 13, 2015 at 05:12:44PM +0100, Paul Burton wrote:
> > After writing the appropriate mask to the cop0 PageMask register, read
> > the register back & check it matches what we want. If it doesn't then
> > the MMU does not support the page size the kernel is configured for and
> > we're better off bailing than continuing to do odd things with TLB
> > exceptions.
> > 
> > Signed-off-by: Paul Burton <paul.burton@imgtec.com>
> > ---
> 
> Hi Ralf,
> 
> This patch is marked as accepted in patchwork[1] but is not present in
> upstream. Did you lose it somehow? Could you please merge it?

No idea what went wrong but I (re-?)applied it.

  Ralf

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