linux-kernel - Re: DeviceTree and children devices

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Date:	Mon, 24 Oct 2011 09:58:39 +0200
From:	Grant Likely <grant.likely@...retlab.ca>
To:	balbi@...com
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Linux USB Mailing List <linux-usb@...r.kernel.org>
Subject: Re: DeviceTree and children devices

On Mon, Oct 24, 2011 at 9:49 AM, Felipe Balbi <balbi@...com> wrote:
> On Mon, Oct 24, 2011 at 09:41:24AM +0200, Grant Likely wrote:
>> On Mon, Oct 24, 2011 at 09:42:28AM +0300, Felipe Balbi wrote:
>> > then I can drop the dwc3 platform_device allocation and all of that
>> > resource copying, etc.
>> >
>> > What do you think ?
>>
>> Looks reasonable to me.  of_platform_populate() should be able to
>> handle the device generation for you here.
>
> Ok cool I looking into that and it handles everything I need. There are
> only three issues which I see:
>
> a) it hardcoded DMA mask to 32-bit. Right ?
> b) it's not using dma_set_coherent_mask()
> c) in case parent is a valid pointer, shouldn't it copy DMA mask from
>        parent ?
>
> I mean (doesn't solve (a) above):
>
> diff --git a/drivers/of/platform.c b/drivers/of/platform.c
> index ed5a6d3..172d4a9 100644
> --- a/drivers/of/platform.c
> +++ b/drivers/of/platform.c
> @@ -204,7 +204,12 @@ struct platform_device *of_platform_device_create_pdata(
>  #if defined(CONFIG_MICROBLAZE)
>        dev->archdata.dma_mask = 0xffffffffUL;
>  #endif
> -       dev->dev.coherent_dma_mask = DMA_BIT_MASK(32);
> +
> +       if (parent)
> +               dma_set_coherent_mask(&dev->dev, parent->coherent_dma_mask);
> +       else
> +               dma_set_coherent_mask(&dev->dev, DMA_BIT_MASK(32));
> +

Right, this does need to be fixed.  The existing code just matched
what the historical powerpc code did, but it is certainly not correct.

g.
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