Re: VAXstation 4000 TURBOchannel not working

[Felix Deichmann <m4j0rd0m0%gmail.com@localhost>]

Am 24.03.2016 um 19:45 schrieb Maciej W. Rozycki:
>   I checked what Linux does and its TC bus driver actually maps whole slots
> one by one temporarily as it walks the TC space and reads ROM headers to
> present for option drivers' use.  It would be enough though to map the
> initial 4MB only to get at the two possible REX ROM locations.  Slots are
> then unmapped and option drivers need to map whatever they need themselves
> as they claim devices.  This is platform independent.

Exactly, one "slot" (4 MB) should be enough at first for the (proto) ROM 
header at 0x3c03e0 or 0x3e0, respectively. If more than one slot is 
required according to the ROM information, remapping with more slots 
could be done.

I would opt to do this for vax alone at the moment, as the generic TC 
code implies BUS_SPACE_MAP_LINEAR and uses pointers for I/O directly. So 
things should be setup correctly before it gets there.

Will give vax-specific ROM header parsing a try soon, as I also can't 
imagine a better way right now.

>   I found out you don't actually need to poke at DWCTX-BX adapter's control
> registers to get the TC option working -- the settings left by the console
> firmware seem adequate, unless you want to make use of the SG map (I
> couldn't be bothered given the amount of other stuff to handle combined
> with the lack of time; perhaps you'll be able to put it in a good use).

Yes, I also left the TC bus adaptor as configured by the firmware.

For DMA, it seems you can switch "direct" DMA to SG DMA by setting a bit 
in the adaptor's CSR at 0x36800000.
I found [2], chapter 19, available online for some more details about 
the TC adaptor, quite interesting.

>   All options I came across had their REX ROM contents right.  The ZLX-E3
> option reports 32MB (i.e. 8), and ZLX-E2 and ZLX-E1 report 16MB and 4MB,
> respectively.

Great, just well-engineered hardware!

Felix


[2] Digital Equipment Corporation. OpenVMS VAX Device Support Manual, 
March 1994. Order Number: AA–PWC8A–TE. 
http://h20565.www2.hpe.com/hpsc/doc/public/display?docId=emr_na-c04623285&lang=en-us&cc=us