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    SubjectRe: [PATCHv7 1/7] iommu/io-pgtable-arm: Add support to use system cache
    On Wed, Nov 11, 2020 at 11:32:42AM +0530, Sai Prakash Ranjan wrote:
    > 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@codeaurora.org>
    > > > ---
    > > > 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;

    Yes, but rejecting the quirk if the walker is coherent (I accidentally said
    "non-coherent" earlier on).

    Will

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