linux-kernel - Re: [PATCH v2 2/7] iommu: mtk_iommu: Lookup phandle to retrieve syscon to infracfg

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Date:   Thu, 26 May 2022 16:22:13 +0800
From:   Yong Wu <yong.wu@...iatek.com>
To:     AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>
CC:     <joro@...tes.org>, <will@...nel.org>, <robh+dt@...nel.org>,
        <krzysztof.kozlowski+dt@...aro.org>, <matthias.bgg@...il.com>,
        <iommu@...ts.linux-foundation.org>,
        <linux-mediatek@...ts.infradead.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <krzysztof.kozlowski@...aro.org>
Subject: Re: [PATCH v2 2/7] iommu: mtk_iommu: Lookup phandle to retrieve
 syscon to infracfg

On Wed, 2022-05-18 at 12:04 +0200, AngeloGioacchino Del Regno wrote:
> This driver will get support for more SoCs and the list of infracfg
> compatibles is expected to grow: in order to prevent getting this
> situation out of control and see a long list of compatible strings,
> add support to retrieve a handle to infracfg's regmap through a
> new "mediatek,infracfg" phandle.
> 
> In order to keep retrocompatibility with older devicetrees, the old
> way is kept in place, but also a dev_warn() was added to advertise
> this change in hope that the user will see it and eventually update
> the devicetree if this is possible.
> 
> Signed-off-by: AngeloGioacchino Del Regno <
> angelogioacchino.delregno@...labora.com>
> ---
>  drivers/iommu/mtk_iommu.c | 40 +++++++++++++++++++++++++----------
> ----
>  1 file changed, 26 insertions(+), 14 deletions(-)
> 
> diff --git a/drivers/iommu/mtk_iommu.c b/drivers/iommu/mtk_iommu.c
> index 71b2ace74cd6..d16b95e71ded 100644
> --- a/drivers/iommu/mtk_iommu.c
> +++ b/drivers/iommu/mtk_iommu.c
> @@ -1134,22 +1134,34 @@ static int mtk_iommu_probe(struct
> platform_device *pdev)
>  	data->protect_base = ALIGN(virt_to_phys(protect),
> MTK_PROTECT_PA_ALIGN);
>  
>  	if (MTK_IOMMU_HAS_FLAG(data->plat_data, HAS_4GB_MODE)) {
> -		switch (data->plat_data->m4u_plat) {
> -		case M4U_MT2712:
> -			p = "mediatek,mt2712-infracfg";
> -			break;
> -		case M4U_MT8173:
> -			p = "mediatek,mt8173-infracfg";
> -			break;
> -		default:
> -			p = NULL;
> +		infracfg = syscon_regmap_lookup_by_phandle(dev-
> >of_node, "mediatek,infracfg");
> +		if (IS_ERR(infracfg)) {
> +			dev_info(dev, "Cannot find phandle to
> mediatek,infracfg:"
> +				      " Please update your
> devicetree.\n");

Remove the log from Robin?

> +			/*
> +			 * Legacy devicetrees will not specify a
> phandle to
> +			 * mediatek,infracfg: in that case, we use the
> older
> +			 * way to retrieve a syscon to infra.
> +			 *
> +			 * This is for retrocompatibility purposes
> only, hence
> +			 * no more compatibles shall be added to this.
> +			 */
> +			switch (data->plat_data->m4u_plat) {
> +			case M4U_MT2712:
> +				p = "mediatek,mt2712-infracfg";
> +				break;
> +			case M4U_MT8173:
> +				p = "mediatek,mt8173-infracfg";
> +				break;
> +			default:
> +				p = NULL;
> +			}

We already use "mediatek,infracfg" property for commonizing. For the
previous SoC, I also prefer to put the string into the platform data.

After this, "->m4u_plat" could be removed. Of course, this is not the
main purpose of this patchset. it also is ok currently.

> +
> +			infracfg =
> syscon_regmap_lookup_by_compatible(p);
> +			if (IS_ERR(infracfg))
> +				return PTR_ERR(infracfg);
>  		}
>  
> -		infracfg = syscon_regmap_lookup_by_compatible(p);
> -
> -		if (IS_ERR(infracfg))
> -			return PTR_ERR(infracfg);
> -
>  		ret = regmap_read(infracfg, REG_INFRA_MISC, &val);
>  		if (ret)
>  			return ret;