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    SubjectRe: [PATCH v2 11/29] iommu/mediatek: Always pm_runtime_get while tlb flush
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    On 13.08.21 08:53, Yong Wu wrote:
    > Prepare for 2 HWs that sharing pgtable in different power-domains.
    >
    > The previous SoC don't have PM. Only mt8192 has power-domain,
    > and it is display's power-domain which nearly always is enabled.

    hi, I see that in mt1873.dtsi, many devices that uses the iommu have the
    'power-domains' property.

    >
    > When there are 2 M4U HWs, it may has problem.
    > In this function, we get the pm_status via the m4u dev, but it don't
    > reflect the real power-domain status of the HW since there may be other
    > HW also use that power-domain.
    >
    > Currently we could not get the real power-domain status, thus always
    > pm_runtime_get here.
    >
    > Prepare for mt8195, thus, no need fix tags here.
    >
    > This patch may drop the performance, we expect the user could
    > pm_runtime_get_sync before dma_alloc_attrs which need tlb ops.
    >

    Could you explain this sentence a bit? should the user call pm_runtime_get_sync
    before calling dma_alloc_attrs?

    Thanks,
    Dafna

    > Signed-off-by: Yong Wu <yong.wu@mediatek.com>
    > ---
    > drivers/iommu/mtk_iommu.c | 5 ++++-
    > 1 file changed, 4 insertions(+), 1 deletion(-)
    >
    > diff --git a/drivers/iommu/mtk_iommu.c b/drivers/iommu/mtk_iommu.c
    > index add23a36a5e2..abc721a1da21 100644
    > --- a/drivers/iommu/mtk_iommu.c
    > +++ b/drivers/iommu/mtk_iommu.c
    > @@ -238,8 +238,11 @@ static void mtk_iommu_tlb_flush_range_sync(unsigned long iova, size_t size,
    >
    > for_each_m4u(data, head) {
    > if (has_pm) {
    > - if (pm_runtime_get_if_in_use(data->dev) <= 0)
    > + ret = pm_runtime_resume_and_get(data->dev);
    > + if (ret < 0) {
    > + dev_err(data->dev, "tlb flush: pm get fail %d.\n", ret);
    > continue;
    > + }
    > }
    >
    > spin_lock_irqsave(&data->tlb_lock, flags);
    >

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