Hi Suman, On 12/23/2013 08:02 PM, Anna, Suman wrote: > Hi Florian, > > On 12/17/2013 06:53 AM, Florian Vaussard wrote: >> 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
