Hi Suman,

On 12/23/2013 08:02 PM, Anna, Suman wrote:

Hi Florian,

On 12/17/2013 06:53 AM, Florian Vaussard wrote:

quoted

Currently, bus_set_iommu() is done in omap_iommu_init(). However,
omap_iommu_probe() can fail in a number of ways, leaving the platform
bus with a dangling reference to a non-initialized iommu. Perform
bus_set_iommu() only if omap_iommu_probe() succeed.

Can you clarify a bit more on what kind of issues you were seeing
specifically? In general, there can be multiple instances of the iommu,
so setting it in probe may not be fixing whatever issue you were seeing.
The current OMAP3 code has only the ISP MMU enabled, but there is also
another one for the IVA MMU (currently not configured by default).
Moving the bus_set_iommu to probe makes sense if only one iommu is
present, so this patch may not be needed at all.

If omap_iommu_probe() fails, the init will have called bus_set_iommu()
anyways. Thus, when a driver request the iommu by calling
iommu_domain_alloc(), it will succeed (but iommu_attach_device() will
fail if I remember). Leaving a driver with a dangling reference to
a phantom iommu is not good IMHO. It will lead to strange behaviours
one day or another.

As for the multiple iommu case, as I do not think it is currently
possible, as bus_type (in this case &platform_bus_type) has only
one struct iommu_ops. bus_set_iommu() will return EBUSY on the
second call. Am I missing something?

Also, the main change in this patch is moving the bus_set_iommu from
omap_iommu_init to omap_iommu_probe, so you should probably leave out
moving the function. The omap_iommu_probe function would anyway need
conversion to using devm_ functions.

This was my first try also, but as bus_set_iommu() needs omap_iommu_ops
(itself depending on several functions), its call must come after the
declaration of omap_iommu_ops. Thus I moved omap_iommu_probe() after
the declaration of omap_iommu_ops. But I can probably use a forward
declaration for omap_iommu_ops, this would be better.

Indeed, we can also convert to devm_.

Regards,

Florian