Re: [PATCH V3 2/3] PCI: rcar: Do not abort on too many inbound dma-ranges

[Marek Vasut <marek.vasut@gmail.com>]

On 10/21/19 12:18 PM, Andrew Murray wrote:
[...]
>>>> In case the "dma-ranges" DT property contains either too many ranges
>>>> or the range start address is unaligned in such a way that populating
>>>> the range into the controller requires multiple entries, a situation
>>>> may occur where all ranges cannot be loaded into the controller.
>>>>
>>>> Currently, the driver refuses to probe in such a situation. Relax this
>>>> behavior, load as many ranges as possible and warn if some ranges do
>>>> not fit anymore.
>>>
>>> What is the motivation for relaxing this?
>>
>> U-Boot can fill the ranges in properly now, the list would be longer in
>> such a case and the driver would fail to probe (because the list is
>> longer than what the hardware can support).
> 
> Is this the U-Boot patch you refer to:
> 
> https://patchwork.ozlabs.org/patch/1129436/

Yes.

> As pci_set_region is called with the same address for PCI and CPU memory
> this implies there is a 1:1 mapping - therefore I don't see a need for
> multiple mappings for each DRAM bank. (Also if this controller has a
> 32 bit limitation, shouldn't this code limit the addresses before calling
> pci_set_region?).
It would certainly be helpful to know about this dma-ranges detail
earlier, this whole thing could've been avoided. Now all I can do is get
that patch reverted for the next U-Boot release.

But this still leaves me with one open question -- how do I figure out
what to program into the PCI controller inbound windows, so that the
controller correctly filters inbound transfers which are targetting
nonexisting memory ?

-- 
Best regards,
Marek Vasut