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Message-ID: <1571117141.19130.82.camel@mhfsdcap03>
Subject: Re: [PATCH v3 6/7] iommu/mediatek: Use writel for TLB range
 invalidation
From:   Yong Wu <yong.wu@mediatek.com>
To:     Robin Murphy <robin.murphy@arm.com>
CC:     Matthias Brugger <matthias.bgg@gmail.com>,
        Joerg Roedel <joro@8bytes.org>,
        Will Deacon <will.deacon@arm.com>, <youlin.pei@mediatek.com>,
        <anan.sun@mediatek.com>, Nicolas Boichat <drinkcat@chromium.org>,
        <cui.zhang@mediatek.com>, <srv_heupstream@mediatek.com>,
        <chao.hao@mediatek.com>, <edison.hsieh@mediatek.com>,
        <linux-kernel@vger.kernel.org>, Evan Green <evgreen@chromium.org>,
        Tomasz Figa <tfiga@google.com>,
        <iommu@lists.linux-foundation.org>,
        <linux-mediatek@lists.infradead.org>,
        <linux-arm-kernel@lists.infradead.org>
Date:   Tue, 15 Oct 2019 13:25:41 +0800
In-Reply-To: <c87e2a9c-5ed3-e44c-3b17-067db173eae9@arm.com>
References: <1571035101-4213-1-git-send-email-yong.wu@mediatek.com>
         <1571035101-4213-7-git-send-email-yong.wu@mediatek.com>
         <c87e2a9c-5ed3-e44c-3b17-067db173eae9@arm.com>
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On Mon, 2019-10-14 at 15:04 +0100, Robin Murphy wrote:
> On 14/10/2019 07:38, 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.
> 
> For Arm CPUs, these registers should be mapped as Device memory, 
> therefore the same-peripheral rule should implicitly enforce that the 
> accesses are made in program order, hence you're unlikely to have seen a 
> problem in reality. However, the logical reasoning for the change seems 
> valid in general, so I'd argue that it's still worth making if only for 
> the sake of good practice:
> 
> Acked-by: Robin Murphy <robin.murphy@arm.com>

Thanks very much for the view. If this patch is not so necessary, I will
remove it this time.

> 
> > Signed-off-by: Anan.Sun <anan.sun@mediatek.com>
> > Signed-off-by: Yong Wu <yong.wu@mediatek.com>
> > ---
> >   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 dbbacc3..d285457 100644
> > --- a/drivers/iommu/mtk_iommu.c
> > +++ b/drivers/iommu/mtk_iommu.c
> > @@ -187,8 +187,7 @@ static void mtk_iommu_tlb_flush_range_sync(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);
> >   
> >   		/* tlb sync */
> >   		ret = readl_poll_timeout_atomic(data->base + REG_MMU_CPE_DONE,
> > 
> 
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