[openib-general] Re: understanding mthca_alloc_db()

[yipee]

Roland Dreier <rdreier <at> cisco.com> writes:
>

[snip]

Thanks for the answers Roland.

>     yipee> The functions defines two types/groups of doorbells. Why
>     yipee> are these doorbells allocated differently (one group starts
>     yipee> at the begining of the array and the other at the end)?
> 
> This is the way the hardware works.

Where can I read about it? I have the documentation file:
InfiniHost_Programmers_Reference_Manual_1_16.pdf
but see no mention of this. Can you give any pointer to this info?

>     yipee> Another thing I noticed is that doorbells are different
>     yipee> between Tavor and Arbel HCA's (e.g. see
>     yipee> update_cons_index(). Is it correct that Arbel doorbells are
>     yipee> only 32 bits wide?
> 
> Sort of.  It is definitely true that Tavor-mode doorbells work
> differently from Arbel/mem-free-mode doorbells.

Again, where can I read about this?

I also have another question:
We would like to do rdma to memory mapped I/O so a remote node can write, 
for example, directly to a device. We mapped some virtual address to 
the physical address of the device. When we tried to register this 
virtual memory area the ib driver failed (get_user_pages() failed).  
Can you please advice about how to make this work?

Thanks,
y