linux-kernel - Re: [PATCH v3 3/7] iommu/mediatek: Disable STANDARD_AXI_MODE in MISC

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Date:   Mon, 25 May 2020 14:14:35 +0800
From:   Yong Wu <yong.wu@...iatek.com>
To:     Chao Hao <chao.hao@...iatek.com>
CC:     Joerg Roedel <joro@...tes.org>, Rob Herring <robh+dt@...nel.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        <iommu@...ts.linux-foundation.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-mediatek@...ts.infradead.org>, <wsd_upstream@...iatek.com>,
        FY Yang <fy.yang@...iatek.com>, Jun Yan <jun.yan@...iatek.com>
Subject: Re: [PATCH v3 3/7] iommu/mediatek: Disable STANDARD_AXI_MODE in
 MISC_CTRL

On Sat, 2020-05-09 at 16:36 +0800, Chao Hao wrote:
> In order to improve performance, we always disable STANDARD_AXI_MODE in
> MISC_CTRL.
> 
> Signed-off-by: Chao Hao <chao.hao@...iatek.com>
> ---
>  drivers/iommu/mtk_iommu.c | 8 +++++++-
>  drivers/iommu/mtk_iommu.h | 1 +
>  2 files changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/iommu/mtk_iommu.c b/drivers/iommu/mtk_iommu.c
> index e7e7c7695ed1..9ede327a418d 100644
> --- a/drivers/iommu/mtk_iommu.c
> +++ b/drivers/iommu/mtk_iommu.c
> @@ -42,6 +42,8 @@
>  #define F_INVLD_EN1				BIT(1)
>  
>  #define REG_MMU_MISC_CTRL			0x048
> +#define F_MMU_STANDARD_AXI_MODE_BIT		(BIT(3) | BIT(19))
> +
>  #define REG_MMU_DCM_DIS				0x050
>  
>  #define REG_MMU_CTRL_REG			0x110
> @@ -585,7 +587,11 @@ static int mtk_iommu_hw_init(const struct mtk_iommu_data *data)
>  	}
>  	writel_relaxed(0, data->base + REG_MMU_DCM_DIS);
>  
> -	if (data->plat_data->reset_axi) {
> +	if (data->plat_data->has_misc_ctrl) {
> +		regval = readl_relaxed(data->base + REG_MMU_MISC_CTRL);
> +		regval &= ~F_MMU_STANDARD_AXI_MODE_BIT;
> +		writel_relaxed(regval, data->base + REG_MMU_MISC_CTRL);
> +	} else if (data->plat_data->reset_axi) {
>  		/* The register is called STANDARD_AXI_MODE in this case */
>  		writel_relaxed(0, data->base + REG_MMU_MISC_CTRL);
>  	}


0x48 is either STANDARD_AXI_MODE or MISC_CTRL.

Thus, 

if (data->plat_data->reset_axi) {
   xxx
} else {  /* MISC_CTRL */
   xxx
}

No need add "has_misc_ctrl".


> diff --git a/drivers/iommu/mtk_iommu.h b/drivers/iommu/mtk_iommu.h
> index 1b6ea839b92c..d711ac630037 100644
> --- a/drivers/iommu/mtk_iommu.h
> +++ b/drivers/iommu/mtk_iommu.h
> @@ -40,6 +40,7 @@ struct mtk_iommu_plat_data {
>  
>  	/* HW will use the EMI clock if there isn't the "bclk". */
>  	bool                has_bclk;
> +	bool		    has_misc_ctrl;
>  	bool                has_vld_pa_rng;
>  	bool                reset_axi;
>  	unsigned char       larbid_remap[MTK_LARB_NR_MAX];