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

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Date:   Wed, 19 Sep 2018 14:06:53 +0000
From:   Laurentiu Tudor <laurentiu.tudor@....com>
To:     Robin Murphy <robin.murphy@....com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>
CC:     Madalin-cristian Bucur <madalin.bucur@....com>,
        Roy Pledge <roy.pledge@....com>, Leo Li <leoyang.li@....com>,
        "shawnguo@...nel.org" <shawnguo@...nel.org>,
        "davem@...emloft.net" <davem@...emloft.net>
Subject: Re: [PATCH 18/21] arm64: dts: ls104xa: set mask to drop TBU ID from
 StreamID

Hi Robin,

On 19.09.2018 16:41, Robin Murphy wrote:
> 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, 

On these lower-end platforms the SID input is configured and documented 
as 8-bit.

> 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.

Yes, on LS2s there are 2 extra-bits in there carrying some signaling. 
However, on LS1s they are not present.

---
Thanks & Best Regards, Laurentiu

> 
>>               #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 */
>>