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Subject: Re: [PATCH 5/6] dma-mapping: support fsl-mc bus
To:     Nipun Gupta <nipun.gupta@nxp.com>, Christoph Hellwig <hch@lst.de>
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From:   Robin Murphy <robin.murphy@arm.com>
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Date:   Fri, 9 Mar 2018 18:50:05 +0000
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On 09/03/18 18:29, Nipun Gupta wrote:
> 
> 
>> -----Original Message-----
>> From: Christoph Hellwig [mailto:hch@lst.de]
>> Sent: Thursday, March 08, 2018 13:11
>>
>> On Tue, Mar 06, 2018 at 04:41:56AM +0000, Nipun Gupta wrote:
>>> Sorry for asking a trivial question - looking into dma_configure() I see that
>>> PCI is used in the start and the end of the API.
>>> In the end part pci_put_host_bridge_device() is called.
>>> So are two bus callbacks something like 'dma_config_start' &
>> 'dma_config_end'
>>> will be required where the former one will return "dma_dev"?
>>
>> I'd just use dma_configure as the callback.
> 
> This would be a decent stuff.

Yes, the PCI version should end up looking a lot like the old 
pci_dma_configure() used to, before everything got pulled together.

>> Currently the of_dma_configure and acpi_dma_configure are only used
>> for PCI anyway, as no one else sets a non-NULL dma dev.
> 
> My understanding is that even the platform bus uses the of_dma_configure
> and probably acpi_dma_configure too. So platform bus may also need the
> callback implemented. Please correct me if my understanding is wrong.

Indeed, platform and AMBA will want an implementation to dispatch 
between {of,acpi}_dma_configre() per the current logic. Host1x doesn't 
seem to care about ACPI so probably wants its own just calling 
of_dma_configure().

> I will submit the patch with 'dma_configure' callback implemented for
> the busses shortly.

Cheers - I've been trying to find some time to take a look myself, but 
having something to review instead would certainly be easier :)

Robin.