linux-kernel - Re: [PATCH 18/21] arm64: dts: ls104xa: set mask to drop TBU ID from StreamID

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Message-ID: <fe2af486-3d7d-a38f-ef62-6754f809298f@arm.com>
Date:   Wed, 19 Sep 2018 14:41:49 +0100
From:   Robin Murphy <robin.murphy@....com>
To:     laurentiu.tudor@....com, devicetree@...r.kernel.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Cc:     madalin.bucur@....com, roy.pledge@....com, leoyang.li@....com,
        shawnguo@...nel.org, davem@...emloft.net
Subject: Re: [PATCH 18/21] arm64: dts: ls104xa: set mask to drop TBU ID from
 StreamID

On 19/09/18 13:36, laurentiu.tudor@....com wrote:
> From: Laurentiu Tudor <laurentiu.tudor@....com>
> 
> The StreamID entering the SMMU is actually a concatenation of the
> SMMU TBU ID and the ICID configured in software.
> Since the TBU ID is internal to the SoC and since we want that the
> actual the ICID configured in software to enter the SMMU witout any
> additional set bits, mask out the TBU ID bits and leave only the
> relevant ICID bits to enter SMMU.
> 
> Signed-off-by: Laurentiu Tudor <laurentiu.tudor@....com>
> ---
>   arch/arm64/boot/dts/freescale/fsl-ls1043a.dtsi | 1 +
>   arch/arm64/boot/dts/freescale/fsl-ls1046a.dtsi | 1 +
>   2 files changed, 2 insertions(+)
> 
> diff --git a/arch/arm64/boot/dts/freescale/fsl-ls1043a.dtsi b/arch/arm64/boot/dts/freescale/fsl-ls1043a.dtsi
> index 8b3eba167508..90296b9fb171 100644
> --- a/arch/arm64/boot/dts/freescale/fsl-ls1043a.dtsi
> +++ b/arch/arm64/boot/dts/freescale/fsl-ls1043a.dtsi
> @@ -226,6 +226,7 @@
>   			compatible = "arm,mmu-500";
>   			reg = <0 0x9000000 0 0x400000>;
>   			dma-coherent;
> +			stream-match-mask = <0x7f00>;

The TBU ID only forms the top 5 bits, so also ignoring bits 9:8 raises 
an eyebrow - if the LS104x SMMU really is configured for 8-bit SID input 
then it's harmless, but if it's actually a 9 or 10-bit configuration 
then you probably want to avoid masking them (or at least document why) 
- IIRC there *was* stuff wired there on LS2085 at least.

Robin.

>   			#global-interrupts = <2>;
>   			#iommu-cells = <1>;
>   			interrupts = <0 142 4>, /* global secure fault */
> diff --git a/arch/arm64/boot/dts/freescale/fsl-ls1046a.dtsi b/arch/arm64/boot/dts/freescale/fsl-ls1046a.dtsi
> index 06863d3e4a7d..15094dd8400e 100644
> --- a/arch/arm64/boot/dts/freescale/fsl-ls1046a.dtsi
> +++ b/arch/arm64/boot/dts/freescale/fsl-ls1046a.dtsi
> @@ -232,6 +232,7 @@
>   			compatible = "arm,mmu-500";
>   			reg = <0 0x9000000 0 0x400000>;
>   			dma-coherent;
> +			stream-match-mask = <0x7f00>;
>   			#global-interrupts = <2>;
>   			#iommu-cells = <1>;
>   			interrupts = <0 142 4>, /* global secure fault */
>