linux-kernel - Re: [PATCH v3 09/33] iommu/mediatek: Remove for_each_m4u in tlb_sync

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Message-ID: <bfa33e94-c2e5-5dab-c9af-b674e1669daa@collabora.com>
Date:   Tue, 4 Jan 2022 16:55:18 +0100
From:   AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>
To:     Yong Wu <yong.wu@...iatek.com>, Joerg Roedel <joro@...tes.org>,
        Rob Herring <robh+dt@...nel.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Will Deacon <will@...nel.org>,
        Robin Murphy <robin.murphy@....com>
Cc:     Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>,
        Tomasz Figa <tfiga@...omium.org>,
        linux-mediatek@...ts.infradead.org, srv_heupstream@...iatek.com,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        iommu@...ts.linux-foundation.org,
        Hsin-Yi Wang <hsinyi@...omium.org>, youlin.pei@...iatek.com,
        anan.sun@...iatek.com, chao.hao@...iatek.com,
        yen-chang.chen@...iatek.com
Subject: Re: [PATCH v3 09/33] iommu/mediatek: Remove for_each_m4u in
 tlb_sync_all

Il 23/09/21 13:58, Yong Wu ha scritto:
> The tlb_sync_all is called from these three functions:
> a) flush_iotlb_all: it will be called for each a iommu HW.
> b) tlb_flush_range_sync: it already has for_each_m4u.
> c) in irq: When IOMMU HW translation fault, Only need flush itself.
> 
> Thus, No need for_each_m4u in this tlb_sync_all. Remove it.
> 
> Signed-off-by: Yong Wu <yong.wu@...iatek.com>
> ---
>   drivers/iommu/mtk_iommu.c | 18 +++++++-----------
>   1 file changed, 7 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/iommu/mtk_iommu.c b/drivers/iommu/mtk_iommu.c
> index 6f4f6624e3ac..0b4c30baa864 100644
> --- a/drivers/iommu/mtk_iommu.c
> +++ b/drivers/iommu/mtk_iommu.c
> @@ -206,19 +206,15 @@ static struct mtk_iommu_domain *to_mtk_domain(struct iommu_domain *dom)
>   
>   static void mtk_iommu_tlb_flush_all(struct mtk_iommu_data *data)
>   {
> -	struct list_head *head = data->hw_list;
> -
> -	for_each_m4u(data, head) {
> -		if (pm_runtime_get_if_in_use(data->dev) <= 0)
> -			continue;
> +	if (pm_runtime_get_if_in_use(data->dev) <= 0)
> +		return;
>   
> -		writel_relaxed(F_INVLD_EN1 | F_INVLD_EN0,
> -			       data->base + data->plat_data->inv_sel_reg);
> -		writel_relaxed(F_ALL_INVLD, data->base + REG_MMU_INVALIDATE);
> -		wmb(); /* Make sure the tlb flush all done */
> +	writel_relaxed(F_INVLD_EN1 | F_INVLD_EN0,
> +		       data->base + data->plat_data->inv_sel_reg);
> +	writel_relaxed(F_ALL_INVLD, data->base + REG_MMU_INVALIDATE);
> +	wmb(); /* Make sure the tlb flush all done */

There aren't a lot of writes here - not anymore, since you are no longer doing
this for_each_m4u()...
...so, please change writel_relaxed() to writel() calls, allowing you to also
remove the write barrier at the end (since in the non relaxed version, order
is already ensured).

>   
> -		pm_runtime_put(data->dev);
> -	}
> +	pm_runtime_put(data->dev);
>   }
>   
>   static void mtk_iommu_tlb_flush_range_sync(unsigned long iova, size_t size,
>