linux-kernel - Re: [PATCH] arm64: dts: fsd: Change the reg properties from 64-bit to 32-bit

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Message-ID: <94af81ef-782a-9cf5-b656-f2c304a8e4ef@arm.com>
Date:   Wed, 16 Nov 2022 12:44:50 +0000
From:   Robin Murphy <robin.murphy@....com>
To:     Arnd Bergmann <arnd@...db.de>,
        Vivek Yadav <vivek.2311@...sung.com>, rcsekar@...sung.com,
        krzysztof.kozlowski+dt@...aro.org,
        Wolfgang Grandegger <wg@...ndegger.com>,
        Marc Kleine-Budde <mkl@...gutronix.de>,
        "David S . Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, pankaj.dubey@...sung.com,
        ravi.patel@...sung.com, Alim Akhtar <alim.akhtar@...sung.com>,
        linux-fsd@...la.com, Rob Herring <robh+dt@...nel.org>
Cc:     linux-can@...r.kernel.org, Netdev <netdev@...r.kernel.org>,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-samsung-soc@...r.kernel.org, devicetree@...r.kernel.org,
        aswani.reddy@...sung.com, sriranjani.p@...sung.com,
        ajaykumar.rs@...sung.com
Subject: Re: [PATCH] arm64: dts: fsd: Change the reg properties from 64-bit to
 32-bit

On 2022-11-16 12:38, Robin Murphy wrote:
> On 2022-11-16 11:16, Arnd Bergmann wrote:
>> On Wed, Nov 16, 2022, at 10:12, Vivek Yadav wrote:
>>> Change the reg properties from 64-bit to 32-bit for all IPs, as none of
>>> the nodes are above 32-bit range in the fsd SoC.
>>>
>>> Since dma-ranges length does not fit into 32-bit size, keep it 64-bit
>>> and move it to specific node where it is used instead of SoC section.
>>
>> I don't think that works, the dma-ranges property is part of the
>> bus, not a particular device:
>>
>>           mdma0: dma-controller@...00000 {
>>               compatible = "arm,pl330", "arm,primecell";
>> -            reg = <0x0 0x10100000 0x0 0x1000>;
>> +            reg = <0x10100000 0x1000>;
>>               interrupts = <GIC_SPI 424 IRQ_TYPE_LEVEL_HIGH>;
>>               #dma-cells = <1>;
>>               clocks = <&clock_imem IMEM_DMA0_IPCLKPORT_ACLK>;
>>               clock-names = "apb_pclk";
>>               iommus = <&smmu_imem 0x800 0x0>;
>> +            #address-cells = <2>;
>> +            #size-cells = <2>;
>> +            dma-ranges = <0x0 0x0 0x0 0x10 0x0>;
>>           };
>>
>> Since the dma-controller has no children, I don't see how this has
>> any effect. Also, translating a 36-bit address into a 32-bit
>> address just means it gets truncated anyway, so there is no
>> point in making it appear to have a larger address range.
> 
> Yes, this is definitely bogus on both counts.

Oh, and also that PL330 can only do 32-bit DMA anyway :)

Thanks,
Robin.