From: Vidya Sagar
> Sent: 09 November 2017 18:41
...
> > And this commit [3] sounds like it describes a similar hardware
> > situation with Tegra where the host bridge intercepts the MSI target
> > address, so writes to it never reach system memory. That means that
> > Tegra doesn't need to allocate system memory at all.
> >
> > Is your system similar? Can you just statically allocate a little bus
> > address space, use that for the MSI target address, and skip the
> > __get_free_pages()?
>
> It is the same system where MSI memory writes don't really make it to
> system memory. But, the addresses mentioned in that patch don't work.
> we are working with hardware folks on understanding the issue better.
...
You do need to make sure that the address you pick will never
be used for a 'dma' transfer.
If the address needs to be inside the (pcie) physical addresses
for system memory then allocating a physical page may be the
safest way to ensure this doesn't happen.
David
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