[PATCHv2 06/19] ARM: OMAP4: PM: Add SAR backup support towards device OFF

[Shilimkar, Santosh]

On Thu, May 17, 2012 at 4:28 AM, Kevin Hilman <khilman at ti.com> wrote:
> Tero Kristo <t-kristo at ti.com> writes:
>
>> From: Santosh Shilimkar <santosh.shilimkar at ti.com>
>>
>> The SAR RAM is maintained during Device OFF mode.
>
> so why is this patch bothering to save and restore it?
>
SAR RAM is maintained(not powered down) but somebody needs to
feel the contents which will be preserved :-)

> -ECONFUSED
>
>> The register layout
>> is fixed in SAR ROM. SAR is split into 4 banks with different
>> privilege accesses based on device type
>>
>>  ---------------------------------------------------------------
>>  Access mode          Bank    Address Range
>>  ---------------------------------------------------------------
>>  HS/GP : Public               1       0x4A32_6000 - 0x4A32_6FFF (4kB)
>>  HS/GP : Public               2       0x4A32_7000 - 0x4A32_73FF (1kB)
>>
>>  HS/EMU : Secured
>>  GP : Public          3       0x4A32_8000 - 0x4A32_87FF (2kB)
>>
>>  HS/GP :Secure
>>  write once.          4       0x4A32_9000 - 0x4A32_93FF (1kB)
>>  ---------------------------------------------------------------
>>
>> The save process is done entirely by software and restore is done by
>> hardware using the auto-restore feature. The restore feature is enabled
>> by default and cannot be disabled. The software must save the data
>> to be restored in a dedicated location in SAR RAM.
>
> Some general comments:
>
> - can the cluster PM notifier be used for the save path?
>
Nope. This is for device OFF only case. CPU Cluster state as such
has no dependency.

> - This patch adds lots of data that is immediately removed by the next
>  patch.  Probably the two just need to be combined.
>
iormap() hunk from this patch can be completely dropped since
it is getting fixed in next patch. Other infrastructure is maintained.

> - BUG_ON() should not be used unless there is absolutely no recovery
>  path, since it casues a full kernel panic.   Instead, some error
>  recovery should be added.
>
WARN_ON should suffice.