arm_memblock_steal() API usage

arm_memblock_steal() API usage

[Taniya Das]

Hi RMK,
I have a requirement where I need around ~100 bytes of memory to save 
contents of
registers to a non-cached area before going into low power mode.

I did do some analysis on a 1GB RAM device of allocating 8 bytes using 
the API and the below was the result
was showing allocating only 8 bytes.

API used : -  arm_memblock_steal(SZ_8, SZ_64K);--> physical address 
returned is 0x3b1f0000

/data/debug/memblock # cat memory

0: 0x00200000..0x3b1effff

1: 0x3b1f0008..0x3b1fffff [0x3b1f0000-0x3b1f0007] only 8 bytes removed.

/data/debug/memblock # cat reserved

0: 0x00204000..0x00c710fb

1: 0x01400000..0x01429b44

2: 0x0ffe0000..0x0ffeffff

3: 0x2d9f3000..0x2d9fffff

4: 0x3b1f0008..0x3b1fffff

But before I can go ahead and use this if you could confirm that it will 
allocate only the size requested or it
will carve out minimum 1MB?
Also is this API advisable for devices with low system RAM?

-- 
Thanks&  Regards,
Taniya Das.

Consultant for Qualcomm Innovation Center, Inc.
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum

arm_memblock_steal() API usage

[Russell King - ARM Linux]

On Tue, Apr 03, 2012 at 09:34:03AM +0530, Taniya Das wrote:
> I have a requirement where I need around ~100 bytes of memory to save  
> contents of
> registers to a non-cached area before going into low power mode.
>
> I did do some analysis on a 1GB RAM device of allocating 8 bytes using  
> the API and the below was the result
> was showing allocating only 8 bytes.
>
> API used : -  arm_memblock_steal(SZ_8, SZ_64K);--> physical address  
> returned is 0x3b1f0000

It's silly to use this for the above purpose.  Why not just use kmalloc
and cache flushing to ensure that the data is pushed out to RAM?

> Also is this API advisable for devices with low system RAM?

No.

arm_memblock_steal() API usage

[Taniya Das]

RMK,

On 03-Apr-12 1:00 PM, Russell King - ARM Linux wrote:
> On Tue, Apr 03, 2012 at 09:34:03AM +0530, Taniya Das wrote:
>> I have a requirement where I need around ~100 bytes of memory to save
>> contents of
>> registers to a non-cached area before going into low power mode.
>>
>> I did do some analysis on a 1GB RAM device of allocating 8 bytes using
>> the API and the below was the result
>> was showing allocating only 8 bytes.
>>
>> API used : -  arm_memblock_steal(SZ_8, SZ_64K);-->  physical address
>> returned is 0x3b1f0000
> It's silly to use this for the above purpose.  Why not just use kmalloc
> and cache flushing to ensure that the data is pushed out to RAM?
We don't want to do a kmalloc and flush, we want to do something similar 
to how OMAP4
does, keeping aside a chunk of RAM for saving the contents. But my only 
concern what will
be the minimum amount of memory allocated by arm_memblock_steal?
>> Also is this API advisable for devices with low system RAM?
> No.


-- 
Thanks&  Regards,
Taniya Das.

Sent by an employee of the Qualcomm Innovation Center, Inc.
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum.