[SeaBIOS] [PATCH] megasas: Add boot support for LSI MegaRAID SAS

[Hannes Reinecke]

On 11/13/2012 09:01 AM, Gerd Hoffmann wrote:
>    Hi,
>
>>> Although valid, it's not a good idea to use memalign_high for
>>> temporary space.  One should use memalign_tmp for that purpose.
>>>
>> The thing here is that megasas_fire_cmd() is a generic function, so it
>> needs to work in both 16 and 32-bit environs. So the frame pointer
>> passed to this function needs to reference the same segment.
>
> 32-bit mode is relaxed, everything is a flat 32bit ptr and all those
> funky segment/offset macros do basically nothing.
>
> For 16-bit mode it is very important to get things right ...
>
>> And this is where things get confused.
>> I've converted the driver to use memalign_tmp() for allocating space for
>> the frame. Which works.
>
> The strategy ahci uses is to memalign_tmp() the data structures needed
> for device probing, so they can easily freed in case the port is unused.
>   When a drive is actually found (and registered) the memory for the data
> structures is allocated again using memalign_low(), so it is permanently
> available, accessible in 16-bit mode and the 16-bit only code paths
> don't have to do any memory allocations when kicking transfers.
>
> I think there are code paths where SET_LOWFLAT & friends are used for
> memory allocated via memalign_tmp(), but that happens in 32bit mode only
> where it doesn't really matter.
>
> See ahci_port_realloc().
>
Ah. Thanks for the explanation.

I've converted it now to use memalign_tmplow(), so everybody should 
be happy.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		      zSeries & Storage
hare at suse.de			      +49 911 74053 688
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