linux-kernel - Re: [PATCH v3 2/3] arm64: dts: Add APM X-Gene DMA device and DMA clock DTS nodes

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Message-ID: <CAFd313zc_4fNMGvVNWqUOP+tzHoaCZDbFKVSyBsmT-OtwzHBHQ@mail.gmail.com>
Date:	Mon, 19 Jan 2015 20:15:54 +0530
From:	Rameshwar Sahu <rsahu@....com>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	vinod.koul@...el.com, dan.j.williams@...el.com,
	dmaengine@...r.kernel.org, linux-kernel@...r.kernel.org,
	devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	ddutile@...hat.com, jcm@...hat.com, patches@....com,
	Loc Ho <lho@....com>
Subject: Re: [PATCH v3 2/3] arm64: dts: Add APM X-Gene DMA device and DMA
 clock DTS nodes

Thanks,
with regards,
Ram


On Mon, Jan 19, 2015 at 8:11 PM, Rameshwar Sahu <rsahu@....com> wrote:
> Hi Arnd,
>
>
>
>
>
>
> Thanks,
> with regards,
> Ram
>
> On Mon, Jan 19, 2015 at 7:10 PM, Arnd Bergmann <arnd@...db.de> wrote:
>>
>> On Monday 19 January 2015 18:11:08 Rameshwar Prasad Sahu wrote:
>> > diff --git a/arch/arm64/boot/dts/apm/apm-storm.dtsi
>> > b/arch/arm64/boot/dts/apm/apm-storm.dtsi
>> > index f1ad9c2..e20da23 100644
>> > --- a/arch/arm64/boot/dts/apm/apm-storm.dtsi
>> > +++ b/arch/arm64/boot/dts/apm/apm-storm.dtsi
>> > @@ -103,6 +103,9 @@
>> >                 #size-cells = <2>;
>> >                 ranges;
>> >
>> > +               /* DDR range is 42-bit addressing */
>> > +               dma-ranges = <0x40 0x0 0x40 0x0 0x1ff 0xffffffff>;
>> > +
>> >
>>
>> The comment above is misleading, and the value is wrong. I assume you
>>
>> copied these from the AMD patch that introduced the respective property.
>
>
> I referred this patch from AMD only.
>>
>>
>> The value should be
>>
>>         dma-ranges = <0x40 0x0 0x40 0x0 0x200 0>;
>
>
> then it should be :
>
> dma-ranges = <0x40 0x0 0x40 0x0 0x400 0>;
>
>
>> to say that any DMA to physical addresses from 0 to 0x3f.ffffffff
>> is disallowed and dma to physical addresses from 0x40.00000000
>> to 0x23f.ffffffff is allowed and gets translated using an
>> identity mapping.
>>
>> I also see that on Mustang, all memory is outside of this range,
>
>
> Do you mean all other device controller node in DT here??
> Basically these are all device controller memory, as what I understood is
> dma-ranges tells about DDR ranges like start address of DDR
> and length.
>
>
>>
>> which is a bit suspicious, while your PCI memory space is
>> included.
>
>
>>
>> It would be best to match the numbers up with your data sheet.
>>
>>         Arnd
>> --
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>
>
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