linux-kernel - Re: [PATCH 2/2] iommu/mediatek: always check runtime PM status in tlb flush range callback

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Message-ID: <afb46ad6ca9477a2bf71233858406caa6ccb1588.camel@mediatek.com>
Date:   Sat, 27 Nov 2021 10:46:54 +0800
From:   Yong Wu <yong.wu@...iatek.com>
To:     Dafna Hirschfeld <dafna.hirschfeld@...labora.com>,
        <iommu@...ts.linux-foundation.org>
CC:     Sebastian Reichel <sebastian.reichel@...labora.com>,
        <kernel@...labora.com>, Joerg Roedel <joro@...tes.org>,
        Will Deacon <will@...nel.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        "moderated list:MEDIATEK IOMMU DRIVER" 
        <linux-mediatek@...ts.infradead.org>,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-arm-kernel@...ts.infradead.org>,
        "open list" <linux-kernel@...r.kernel.org>,
        <linux-media@...r.kernel.org>
Subject: Re: [PATCH 2/2] iommu/mediatek: always check runtime PM status in
 tlb flush range callback

On Mon, 2021-11-22 at 12:44 +0200, Dafna Hirschfeld wrote:
> From: Sebastian Reichel <sebastian.reichel@...labora.com>
> 
> In case of v4l2_reqbufs() it is possible, that a TLB flush is done
> without runtime PM being enabled. In that case the "Partial TLB flush
> timed out, falling back to full flush" warning is printed.
> 
> Commit c0b57581b73b ("iommu/mediatek: Add power-domain operation")
> introduced has_pm as optimization to avoid checking runtime PM
> when there is no power domain attached. But without the PM domain
> there is still the device driver's runtime PM suspend handler, which
> disables the clock. Thus flushing should also be avoided when there
> is no PM domain involved.
> 
> Signed-off-by: Sebastian Reichel <sebastian.reichel@...labora.com>
> Reviewed-by: Dafna Hirschfeld <dafna.hirschfeld@...labora.com>

Reviewed-by: Yong Wu <yong.wu@...iatek.com>

> ---
>  drivers/iommu/mtk_iommu.c | 10 +++-------
>  1 file changed, 3 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/iommu/mtk_iommu.c b/drivers/iommu/mtk_iommu.c
> index 28dc4b95b6d9..b0535fcfd1d7 100644
> --- a/drivers/iommu/mtk_iommu.c
> +++ b/drivers/iommu/mtk_iommu.c
> @@ -227,16 +227,13 @@ static void
> mtk_iommu_tlb_flush_range_sync(unsigned long iova, size_t size,
>  					   size_t granule,
>  					   struct mtk_iommu_data *data)
>  {
> -	bool has_pm = !!data->dev->pm_domain;
>  	unsigned long flags;
>  	int ret;
>  	u32 tmp;
>  
>  	for_each_m4u(data) {
> -		if (has_pm) {
> -			if (pm_runtime_get_if_in_use(data->dev) <= 0)
> -				continue;
> -		}
> +		if (pm_runtime_get_if_in_use(data->dev) <= 0)
> +			continue;
>  
>  		spin_lock_irqsave(&data->tlb_lock, flags);
>  		writel_relaxed(F_INVLD_EN1 | F_INVLD_EN0,
> @@ -261,8 +258,7 @@ static void
> mtk_iommu_tlb_flush_range_sync(unsigned long iova, size_t size,
>  		writel_relaxed(0, data->base + REG_MMU_CPE_DONE);
>  		spin_unlock_irqrestore(&data->tlb_lock, flags);
>  
> -		if (has_pm)
> -			pm_runtime_put(data->dev);
> +		pm_runtime_put(data->dev);
>  	}
>  }
>