linux-kernel - Re: [PATCH] ARM: keystone: add bus notifier to set dma_pfn

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Date:	Mon, 13 Oct 2014 10:13:07 -0400
From:	Murali Karicheri <m-karicheri2@...com>
To:	Arnd Bergmann <arnd@...db.de>
CC:	<linux-arm-kernel@...ts.infradead.org>, <linux@....linux.org.uk>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ARM: keystone: add bus notifier to set dma_pfn_offset
 for pci devices

On 10/11/2014 04:37 PM, Arnd Bergmann wrote:
> On Friday 10 October 2014 20:04:57 Santosh Shilimkar wrote:
>> On 10/10/14 5:37 PM, Murali Karicheri wrote:
>>> Based on this, dma configuration parameters get set for the device which
>>> is probed through DT.
>>>
>>> As PCI devices are attached to the PCI bus during scan, and we don't
>>> have DT nodes, we could use similar mechanism to pass the dma-range info
>>> from parent host platform device to the PCI devices by adding an
>>> of_pci_dma_configure() API and hook it to the PCI probe path some where?
>>> Please comment on this so that I can work on the right solution to
>>> address this issue for Keystone.
>>>
>> Adding the DT node parsing code in PCI bus probe path is the right way
>> to go about it. You could re-use some of the helpers from dma parsing
>> code.
>>
>> I let Arnd comment if he disagrees, otherwise I suggest to create an
>> RFC patch and post it on the list. We can take it from there.
>
> Yes, I think that is the correct way forward, we need this anyway to
> handle IOMMUs correctly, following the patches that Will Deacon did
> for platform device IOMMU configuration.
Arnd,

Could you point me to a thread/link for Will Deacon's IOMMU work? Is it 
part of the kernel already?

Murali
>
>> That also reminded me xhci host code issue with dma-ranges since the
>> devices are manually created there. I will review that thread as
>> well after this merge window.
>
> Right, manually created devices are always problematic, you should
> try to avoid those.
>
> 	Arnd


-- 
Murali Karicheri
Linux Kernel, Texas Instruments
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