[parisc-linux] Re: CCIO dma io_command and related io_tlb format questions.

[Grant Grundler <grundler@parisc-linux.org>]

On Mon, Oct 09, 2006 at 11:41:11AM +0200, Joel Soete wrote:
> Hello Grant,
> 
> I back port the sba sg list manager in ccio-dma on my d380 (not enough time to
> test c110).
...

Sounds like you have some debugging to do still...I'll try to
answer the questions below.

> That said, there are no public doc of this IO stuff

There is none for CCIO. And I no longer have access to those
documents (deleted them from my laptop/workstations).
You'd need access to U2/Uturn ERS via OSDL.


> and so I didn't change those 2 hunks:
> [snip]
> static CCIO_INLINE void
> ccio_clear_io_tlb(struct ioc *ioc, dma_addr_t iovp, size_t byte_cnt)
...
> ccio_ioc_init(struct ioc *ioc)
...
> About which cames to me 2 questions:
>    1/ what is supposed to contain an io_tlb entry:

You want to know the layout of the "ioc_command" register.
It is a combination of iovp and command.


>       a io (page size) address as seems to say the value
>      ("CMD_TLB_PURGE | iovp") in ccio_clear_io_tlb()

Offhand I'm not sure of the exact split but guess it's
lower 12 bits for command and upper 20 bits for IO Virtual Page
as used in ccio_clear_io_tlb().

>       or a memory page size should be splited in
>       severall tlb entries per ioc->chainid_shift?

ccio_ioc_init is just clearing the entire IO TLB.
We know there are only "1<<CCIO_CHAINID_SHIFT" IO TLB entries.
See comments above where CCIO_CHAINID_SHIFT is defined.
ccio_clear_io_tlb() is just purging all of them.

>    2/ what is supposed to contain the ccio io_command register, I mean that
>       I don't understand what seems to me to be different io_command
>       contents for CMD_TLB_DIRECT_WRITE or CMD_TLB_PURGE?

Generally we only need to use CMD_TLB_PURGE to avoid use of stale entries.
You shouldn't need to change the uses of CMD_TLB_DIRECT_WRITE.

> If you still have (or access to) this internal doc, it would be great if you
> could find some time to explain me those stuff.

Sorry - I don't.

Hope that helps,
grant
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