[PATCH v2 4/4] iommu: Get DT/ACPI parsing into the proper probe path

[William McVicker]

On 04/22/2025, Jason Gunthorpe wrote:
> On Tue, Apr 22, 2025 at 02:55:28PM -0700, William McVicker wrote:
> 
> > On this note, I was looking through `of_dma_configure_id()` and am also
> > wondering if we may hit other race conditions if the device is still being
> > probed and the dma properties (like the coherent dma mask) haven't been fully
> > populated? Just checking if the driver is bound, doesn't seem like enough to
> > start configuring the DMA when async probing can happen.
> 
> I think the reasoning at work here is that the plugin path for a
> struct device should synchronously setup the iommu.
> 
> There is enough locking there that the iommu code won't allow the
> device plugin to continue until the iommu is fully setup under the
> global lock.
> 
> The trick of using dev->driver is only a way to tell if this function
> is being called from the driver plugin path just before starting the
> driver, or from the iommu code just before configuring the iommu.
> 
> Given that explanation can you see issues with of_dma_configure_id() ?
> 
> Jason

I think the only concern is when a driver calls dma_set_mask_and_coherent() in
it's probe function. If we can handle that case in an asynchrounous manner,
then I think we are good.

Thanks,
Will