On 10/7/2010 9:01 AM, Laurent Pinchart wrote:
On Thursday 07 October 2010 10:32:42 Russell King - ARM Linux wrote:
ARMv6 and above don't like having multiple mappings with different
memory type/shareability/cache attributes. It's architecturally
forbidden.
So if you want non-cacheable memory and you want to be architecturally
compliant, you have to exclude it from the kernel's direct-mapped
memory mapping.
That's why Omar's patch uses 'mem=' to exclude system memory from the kernel
mappings. That's not ideal though, as that memory will be wasted forever,
hence my comments regarding whether a non-cacheable mapping was really
required.
it is not ideal to waste that memory, but strictly speaking old bootmem
does the same, as no one will be touching that memory. i.e. you compile
bridge as a module but you never insmod it, the reserved bootmem space
is there for bridge anyway; same for bootargs tweaking, if you need
dspbridge and are going to use it then you set aside some memory for it.
What might be a pain for end-user, is to have drivers that need to do
tweaking to bootargs to work; but right now that is a requirement, until
a better solution is found/created.
Regards,
Omar
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