linux-kernel - Re: [PATCH v2 1/3] dmaengine: Add support for APM X-Gene SoC DMA engine driver

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Date:	Wed, 14 Jan 2015 14:56:33 +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 v2 1/3] dmaengine: Add support for APM X-Gene SoC DMA
 engine driver

Hi Arnd,





Thanks,
with regards,
Ram


On Tue, Jan 13, 2015 at 12:25 AM, Arnd Bergmann <arnd@...db.de> wrote:
> On Monday 12 January 2015 14:40:09 Rameshwar Sahu wrote:
>> > +
>> > +       dma_set_mask_and_coherent(&pdev->dev,
>> > +                                 (sizeof(dma_addr_t) == sizeof(u64)) ?
>> > +                                 DMA_BIT_MASK(64) : DMA_BIT_MASK(32));
>> > +
>>
>
> I commented on this on v1 already: always set the device specific mask here,
> it's independent of the CPU architecture, but do check the return value.
>
Got it, I will set first 64 bit dma mask here  due to device support
64 bit address dma operations, and fall down to 32 - bit in case
failure with 64 bit.


> Also add the correct dma-ranges property in the parent, or else this will
> fail in the future once we add proper checks to dma_set_mask.

I see arch/arm64 kernel doesn't use dma range value parsed from
dma-range property currently, I will check it more.
It doesn't use dma_pfn_offset value calculated by the dma-ranges in
dma mapping API.
dma-ranges value should test properly before adding.
Is there any use to add this dma-ranges properly if arch code doesn't support ??

>
>         Arnd
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