Re: [PATCHv7 1/7] iommu/io-pgtable-arm: Add support to use system cache

[Sai Prakash Ranjan]

On 2020-11-10 17:48, Will Deacon wrote:
> On Fri, Oct 30, 2020 at 02:53:08PM +0530, Sai Prakash Ranjan wrote:
> > Add a quirk IO_PGTABLE_QUIRK_SYS_CACHE to override the
> > attributes set in TCR for the page table walker when
> > using system cache.
> >
> > Signed-off-by: Sai Prakash Ranjan <saiprakash.ranjan@xxxxxxxxxxxxxx>
> > ---
> >  drivers/iommu/io-pgtable-arm.c | 7 ++++++-
> >  include/linux/io-pgtable.h     | 4 ++++
> >  2 files changed, 10 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/iommu/io-pgtable-arm.c 
> > b/drivers/iommu/io-pgtable-arm.c
> > index a7a9bc08dcd1..a356caf1683a 100644
> > --- a/drivers/iommu/io-pgtable-arm.c
> > +++ b/drivers/iommu/io-pgtable-arm.c
> > @@ -761,7 +761,8 @@ arm_64_lpae_alloc_pgtable_s1(struct io_pgtable_cfg 
> > *cfg, void *cookie)
> >
> >  	if (cfg->quirks & ~(IO_PGTABLE_QUIRK_ARM_NS |
> >  			    IO_PGTABLE_QUIRK_NON_STRICT |
> > -			    IO_PGTABLE_QUIRK_ARM_TTBR1))
> > +			    IO_PGTABLE_QUIRK_ARM_TTBR1 |
> > +			    IO_PGTABLE_QUIRK_SYS_CACHE))
> >  		return NULL;
> >
> >  	data = arm_lpae_alloc_pgtable(cfg);
> > @@ -773,6 +774,10 @@ arm_64_lpae_alloc_pgtable_s1(struct 
> > io_pgtable_cfg *cfg, void *cookie)
> >  		tcr->sh = ARM_LPAE_TCR_SH_IS;
> >  		tcr->irgn = ARM_LPAE_TCR_RGN_WBWA;
> >  		tcr->orgn = ARM_LPAE_TCR_RGN_WBWA;
> > +	} else if (cfg->quirks & IO_PGTABLE_QUIRK_SYS_CACHE) {
> > +		tcr->sh = ARM_LPAE_TCR_SH_OS;
> > +		tcr->irgn = ARM_LPAE_TCR_RGN_NC;
> > +		tcr->orgn = ARM_LPAE_TCR_RGN_WBWA;
>
> Given that this only applies in the case where then page-table walker 
> is
> non-coherent, I think we'd be better off renaming the quirk to 
> something
> like IO_PGTABLE_QUIRK_ARM_OUTER_WBWA and then rejecting it in the
> non-coherent case.

Do you mean like below?

diff --git a/drivers/iommu/io-pgtable-arm.c 
b/drivers/iommu/io-pgtable-arm.c
index a7a9bc08dcd1..94de1f71db42 100644
--- a/drivers/iommu/io-pgtable-arm.c
+++ b/drivers/iommu/io-pgtable-arm.c
@@ -776,7 +776,10 @@ arm_64_lpae_alloc_pgtable_s1(struct io_pgtable_cfg 
*cfg, void *cookie)
        } else {
                tcr->sh = ARM_LPAE_TCR_SH_OS;
                tcr->irgn = ARM_LPAE_TCR_RGN_NC;
-               tcr->orgn = ARM_LPAE_TCR_RGN_NC;
+               if (!(cfg->quirks & IO_PGTABLE_QUIRK_ARM_OUTER_WBWA))
+                       tcr->orgn = ARM_LPAE_TCR_RGN_NC;
+               else
+                       tcr->orgn = ARM_LPAE_TCR_RGN_WBWA;
        }

        tg1 = cfg->quirks & IO_PGTABLE_QUIRK_ARM_TTBR1;


Thanks,
Sai

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