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From:   Hsin-Yi Wang <hsinyi@chromium.org>
Date:   Tue, 24 Aug 2021 15:10:12 +0800
Message-ID: <CAJMQK-hkufqh2vaEKcuO+k0v2SzpCHcyZuEqrvJ__rrAek2P0A@mail.gmail.com>
Subject: Re: [PATCH v2 11/29] iommu/mediatek: Always pm_runtime_get while tlb flush
To:     Yong Wu <yong.wu@mediatek.com>
Cc:     Joerg Roedel <joro@8bytes.org>, Rob Herring <robh+dt@kernel.org>,
        Matthias Brugger <matthias.bgg@gmail.com>,
        Will Deacon <will@kernel.org>,
        Robin Murphy <robin.murphy@arm.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>,
        Evan Green <evgreen@chromium.org>,
        Tomasz Figa <tfiga@google.com>,
        Tomasz Figa <tfiga@chromium.org>,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-mediatek@lists.infradead.org>, srv_heupstream@mediatek.com,
        Devicetree List <devicetree@vger.kernel.org>,
        lkml <linux-kernel@vger.kernel.org>,
        "moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" 
        <linux-arm-kernel@lists.infradead.org>,
        iommu@lists.linux-foundation.org, youlin.pei@mediatek.com,
        Nicolas Boichat <drinkcat@chromium.org>, anan.sun@mediatek.com,
        chao.hao@mediatek.com
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On Fri, Aug 13, 2021 at 2:57 PM Yong Wu <yong.wu@mediatek.com> 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.
>
> 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.

Can you check if there are existing users that need to add this change?


>
> Signed-off-by: Yong Wu <yong.wu@mediatek.com>
> ---
<snip>