Re: [PATCH] iommu: io-pgtable: Support non-coherent page tables

[Vivek Gautam]

On Thu, May 16, 2019 at 5:03 AM Bjorn Andersson
<bjorn.andersson@xxxxxxxxxx> wrote:
>
> Describe the memory related to page table walks as non-cachable for iommu
> instances that are not DMA coherent.
>
> Signed-off-by: Bjorn Andersson <bjorn.andersson@xxxxxxxxxx>
> ---
>  drivers/iommu/io-pgtable-arm.c | 12 +++++++++---
>  1 file changed, 9 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/iommu/io-pgtable-arm.c b/drivers/iommu/io-pgtable-arm.c
> index 4e21efbc4459..68ff22ffd2cb 100644
> --- a/drivers/iommu/io-pgtable-arm.c
> +++ b/drivers/iommu/io-pgtable-arm.c
> @@ -803,9 +803,15 @@ arm_64_lpae_alloc_pgtable_s1(struct io_pgtable_cfg *cfg, void *cookie)
>                 return NULL;
>
>         /* TCR */
> -       reg = (ARM_LPAE_TCR_SH_IS << ARM_LPAE_TCR_SH0_SHIFT) |
> -             (ARM_LPAE_TCR_RGN_WBWA << ARM_LPAE_TCR_IRGN0_SHIFT) |
> -             (ARM_LPAE_TCR_RGN_WBWA << ARM_LPAE_TCR_ORGN0_SHIFT);
> +       if (cfg->quirks & IO_PGTABLE_QUIRK_NO_DMA) {
> +               reg = (ARM_LPAE_TCR_SH_IS << ARM_LPAE_TCR_SH0_SHIFT) |
> +                     (ARM_LPAE_TCR_RGN_WBWA << ARM_LPAE_TCR_IRGN0_SHIFT) |
> +                     (ARM_LPAE_TCR_RGN_WBWA << ARM_LPAE_TCR_ORGN0_SHIFT);
> +       } else {
> +               reg = (ARM_LPAE_TCR_SH_IS << ARM_LPAE_TCR_SH0_SHIFT) |
> +                     (ARM_LPAE_TCR_RGN_NC << ARM_LPAE_TCR_IRGN0_SHIFT) |
> +                     (ARM_LPAE_TCR_RGN_NC << ARM_LPAE_TCR_ORGN0_SHIFT);
> +       }

This looks okay to me based on the discussion that we had on a similar
patch that I
posted. So,
Reviewed-by: Vivek Gautam <vivek.gautam@xxxxxxxxxxxxxx>

[1] https://lore.kernel.org/patchwork/patch/1032939/

Thanks & regards
Vivek

>
>         switch (ARM_LPAE_GRANULE(data)) {
>         case SZ_4K:
> --
> 2.18.0
>
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