[U-Boot] [PATCH V5 4/4] edminiv2: add mvsata_ide and cmd_ide support

[Albert ARIBAUD <albert.aribaud@free.fr>]

Le 04/08/2010 09:23, Albert ARIBAUD a ?crit :
 > Le 04/08/2010 08:08, Prafulla Wadaskar a ?crit :

 >> 3. Instead of adding fixed 41/50 usec delay between the writes to
 >> Scontrol It would be good if you can check/poll some status bit
 >> associated with IDE controller, this will make mvsata driver rock
 >> solid on any platform.
 >
 > I've looked up the marvell kirkwood and orion docs for such a control
 > bit but found none. I'll look it up again, however it might help if
 > you can find someone inside Marvell who would, and could, provide the
 > info.

I think I've found out how it works.

I initially thought the DET field in SControl was a sort of reset line, 
and that writing a 1 would put the controller in continuous reset and 
writing a 0 to put it out of reset.

But actually, DET is a command field : a write of 1 starts the reset 
sequence immediately: the DET field of the SStatus register will go from 
0 to 3 (possibly passing through 1).

Then you can set SControl's DET back to 0 so that you can use the port.

Thus the init sequence becomes: write 3 to SControl's IPM and 1 to DET, 
read SStatus until its DET field is 3, write 0 to SControl's DET.

However I'll keep a timeout value in the status read loop, because you 
can't expect SStatus to become 3: it could stay 0 if no drive is 
connected, for instance. If I did not keep a timeout, u-boot would 
freeze. :/

Amicalement,
-- 
Albert.