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

tg1 = cfg->quirks & IO_PGTABLE_QUIRK_ARM_TTBR1;

Thanks,
Sai

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