linux-kernel - Re: [PATCH 1/3] dt-bindings: memory: mediatek: Add support of unmanaged iommu domain

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Date:   Mon, 30 Jan 2023 11:58:38 +0000
From:   Robin Murphy <robin.murphy@....com>
To:     Alexandre Bailon <abailon@...libre.com>, yong.wu@...iatek.com,
        joro@...tes.org, will@...nel.org
Cc:     matthias.bgg@...il.com, krzysztof.kozlowski@...aro.org,
        robh+dt@...nel.org, iommu@...ts.linux.dev,
        linux-mediatek@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org
Subject: Re: [PATCH 1/3] dt-bindings: memory: mediatek: Add support of
 unmanaged iommu domain

On 2023-01-30 10:27, Alexandre Bailon wrote:
> Currently, the only way to have an unmanaged domain for a device
> is having a dedicated iova region or bank.
> This adds a new bit to MTK_M4U_ID that allows defining devices
> that needs unmanaged iommu domain.

These are details of Linux-specific usage policy, so don't belong in DT 
bindings. I believe the driver already has some internal data to make 
its own assignment of particular devices into particular groups, so 
please just add to that.

Thanks,
Robin.

> Signed-off-by: Alexandre Bailon <abailon@...libre.com>
> ---
>   include/dt-bindings/memory/mtk-memory-port.h | 3 +++
>   1 file changed, 3 insertions(+)
> 
> diff --git a/include/dt-bindings/memory/mtk-memory-port.h b/include/dt-bindings/memory/mtk-memory-port.h
> index 2f68a0511a257..86896c776691a 100644
> --- a/include/dt-bindings/memory/mtk-memory-port.h
> +++ b/include/dt-bindings/memory/mtk-memory-port.h
> @@ -7,11 +7,14 @@
>   #define __DT_BINDINGS_MEMORY_MTK_MEMORY_PORT_H_
>   
>   #define MTK_LARB_NR_MAX			32
> +#define MTK_UNMANAGED_DEVICE            (1 << 31)
>   
>   #define MTK_M4U_ID(larb, port)		(((larb) << 5) | (port))
>   #define MTK_M4U_TO_LARB(id)		(((id) >> 5) & 0x1f)
>   #define MTK_M4U_TO_PORT(id)		((id) & 0x1f)
> +#define MTK_M4U_UNMANAGED(id)		((id) & MTK_UNMANAGED_DEVICE)
>   
>   #define MTK_IFAIOMMU_PERI_ID(port)	MTK_M4U_ID(0, port)
> +#define MTK_M4U_UNMANAGED_ID(larb, port) (MTK_M4U_ID(larb, port) | MTK_UNMANAGED_DEVICE)
>   
>   #endif