Re: [PATCH v4 1/6] of: iommu: add ptr to OF node arg to of_iommu_configure()

[Murali Karicheri]

On 01/29/2015 07:24 PM, Laurent Pinchart wrote:
> Hi Rob,
>
> On Thursday 29 January 2015 10:49:38 Rob Herring wrote:
> > On Wed, Jan 28, 2015 at 5:32 PM, Laurent Pinchart wrote:
> > > On Wednesday 28 January 2015 13:32:19 Will Deacon wrote:
> > > > On Wed, Jan 28, 2015 at 01:15:10PM +0000, Laurent Pinchart wrote:
> > > > > On Wednesday 28 January 2015 12:29:42 Will Deacon wrote:
> > > > > > On Wed, Jan 28, 2015 at 12:23:03PM +0000, Laurent Pinchart wrote:
> > > > > > > On Wednesday 28 January 2015 11:33:00 Will Deacon wrote:
> > > > > > > > On Mon, Jan 26, 2015 at 06:49:01PM +0000, Murali Karicheri wrote:
> > > > > > > > On 01/25/2015 08:32 AM, Laurent Pinchart wrote:
> > > > > > > > > > On Friday 23 January 2015 17:32:34 Murali Karicheri wrote:
> > > > > > > > > > > Function of_iommu_configure() is called from of_dma_configure()
> > > > > > > > > > > to setup iommu ops using DT property. This API is currently used
> > > > > > > > > > > for platform devices for which DMA configuration (including iommu
> > > > > > > > > > > ops) may come from device's parent. To extend this functionality
> > > > > > > > > > > for PCI devices, this API need to take a parent node ptr as an
> > > > > > > > > > > argument instead of assuming device's parent. This is needed since
> > > > > > > > > > > for PCI, the dma configuration may be defined in the DT node of
> > > > > > > > > > > the root bus bridge's parent device. Currently only dma-range is
> > > > > > > > > > > used for PCI and iommu is not supported. So return error if the
> > > > > > > > > > > device is PCI.
> >
> > [...]
> >
> > > > > If I understand Murali's patch set right (please correct me if that's
> > > > > not the case) the PCI code walks up the DT nodes hierarchy to the
> > > > > parent node that contains the iommus attribute and passes a pointer to
> > > > > that node to this function. It's thus a PCI-specific solution. As a
> > > > > temporary hack that's OK I suppose, but if implementing it right
> > > > > straight away isn't difficult that would be better.
> > > >
> > > > It looks to me like the code walks the PCI topology to get the DT node
> > > > for the host controller, and passes *that* to of_dma_configure. That
> > > > sounds like the right thing to do to me, especially since the PCI
> > > > topology is likely not encoded in the device-tree. So actually, it is
> > > > passing the first parent node afaict.
> > >
> > > Indeed, that's right. I forgot for a moment that we have non-DT devices
> > > ;-)
> > >
> > > Acked-by: Laurent Pinchart<laurent.pinchart@xxxxxxxxxxxxxxxx>
> > >
> > > Murali, nitpicking a bit, shouldn't the iommu_np parameter be renamed ? It
> > > points to the node containing the iommus parameter, not to the iommu node,
> > > so the current name is slightly confusing. A brief kerneldoc above the
> > > function would also help. This can be the subject of a separate patch.
> >
> > It was more confusing having np and node within the function.
>
> Agreed.
>
> How about master_np or iommu_master_np ? The latter might be a bit long.
Probabaly master_np suffice as this function is named 
of_iommu_configure(). I will update it.

--
Murali Karicheri
Linux Kernel, Texas Instruments
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/