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SubjectRe: [PATCH v2 3/4] iommu/mediatek: Use writel for TLB range invalidation
On Wed, Oct 09, 2019 at 09:19:02PM +0800, Yong Wu wrote:
> Use writel for the register F_MMU_INV_RANGE which is for triggering the
> HW work. We expect all the setting(iova_start/iova_end...) have already
> been finished before F_MMU_INV_RANGE.
>
> Signed-off-by: Anan.Sun <anan.sun@mediatek.com>
> Signed-off-by: Yong Wu <yong.wu@mediatek.com>
> ---
> This is a improvement rather than fixing a issue.
> ---
> drivers/iommu/mtk_iommu.c | 3 +--
> 1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/drivers/iommu/mtk_iommu.c b/drivers/iommu/mtk_iommu.c
> index 24a13a6..607f92c 100644
> --- a/drivers/iommu/mtk_iommu.c
> +++ b/drivers/iommu/mtk_iommu.c
> @@ -187,8 +187,7 @@ static void mtk_iommu_tlb_add_flush(unsigned long iova, size_t size,
> writel_relaxed(iova, data->base + REG_MMU_INVLD_START_A);
> writel_relaxed(iova + size - 1,
> data->base + REG_MMU_INVLD_END_A);
> - writel_relaxed(F_MMU_INV_RANGE,
> - data->base + REG_MMU_INVALIDATE);
> + writel(F_MMU_INV_RANGE, data->base + REG_MMU_INVALIDATE);

I don't understand this change.

Why is it an "improvement" and which accesses are you ordering with the
writel?

Will

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