Bug 205201 - Booting halts if Dawicontrol DC-2976 UW SCSI board installed, unless RAM size limited to 3500M

[Christoph Hellwig]

On Wed, Nov 27, 2019 at 08:56:25AM +0200, Mike Rapoport wrote:
> On Tue, Nov 26, 2019 at 05:40:26PM +0100, Christoph Hellwig wrote:
> > On Tue, Nov 26, 2019 at 12:26:38PM +0100, Christian Zigotzky wrote:
> > > Hello Christoph,
> > >
> > > The PCI TV card works with your patch! I was able to patch your Git kernel 
> > > with the patch above.
> > >
> > > I haven't found any error messages in the dmesg yet.
> > 
> > Thanks.  Unfortunately this is a bit of a hack as we need to set
> > the mask based on runtime information like the magic FSL PCIe window.
> > Let me try to draft something better up, and thanks already for testing
> > this one!
> 
> Maybe we'll simply force bottom up allocation before calling
> swiotlb_init()? Anyway, it's the last memblock allocation.

So I think we should go with this fix (plus a source code comment) for
now.  Revamping the whole memory initialization is going to take a
while, and this fix also is easily backportable.