Misunderstanding with function cpm_dpalloc in Linux 2.6.x

[Pantelis Antoniou]

On Wednesday 25 January 2006 15:48, Laurent Lagrange wrote:
> 
> Hello,
> 
> I work on MPC boards with Linux 2.6.9 and I have a problem with the
> cpm_dpalloc function.
> 
> In the file cpm2_common.c the function "uint cpm_dpalloc(uint size, uint
> align)" is intended
> to allocate a piece of memory in the dpram. This piece of memory has at
> least "size" bytes
> and I beleived that the returned address should be aligned on "align" bytes.
> 
> This function calls "void *rh_alloc(rh_info_t * info, int size, const char
> *owner)" from rheap.c file.
> In this function the alignment is only used to calculate the right size with
> the formula :
> size = (size + (info->alignment - 1)) & ~(info->alignment - 1);
> It seems to be right but the alignment is not used to retreive an aligned
> start address.
> 
> So if I do the following sequential calls, I have the following results :
> cpm_dpalloc(16, 8)	-> 	0XC0		-> right aligned
> cpm_dpalloc(64, 64)	-> 	0XD0		-> wrong aligned -> must be 0x100
> cpm_dpalloc(16, 8)	-> 	0X110		-> right aligned but wrong to use
> cpm_dpalloc(24, 8)	-> 	0X1200		-> right aligned but wrong to use
> 
> I can have the wanted values if instead of size, I try to allocate (size +
> align - 1) bytes
> but I don't think it is the solution.
> 
> Perhaps, I don't understand the allocation theory.
> Any idea ?
> 
> Thanks all
> Laurent
> 
> 

Laurent Hi,

Yes this is a know bug. This patch fixes it.

Marcelo, please apply - we have this hanging for quite a while.

Pantelis
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