On 25/07/17 16:27, Andrii Anisov wrote:
Hello Julien,
Hi Andrii,
On 25.07.17 17:23, Julien Grall wrote:
I think this is by chance rather than by design. The first question to
answer is why a Firmware would specify twice the same memory banks? Is
it valid from the specification?
Yep, that is the question.
Regardless that, it looks like to me that the device-tree you give to
the board should not contain the memory nodes.
The device-tree is provided by vendor in that form, and u-boot is
theirs. It seems to me that they do not really care since the kernel
tolerates duplication.
I have seen work on this board for the past year and it is the first
time I have seen a complain about memory overlap. So why this sudden
change? Is that a comment from the vendor or your guess?
ps. Linux kernel does tolerate duplicated memory nodes by merging
memory blocks. I.e. memblock_add_range() function is commented as
following:
/**
* memblock_add_range - add new memblock region
* @type: memblock type to add new region into
* @base: base address of the new region
* @size: size of the new region
* @nid: nid of the new region
* @flags: flags of the new region
*
* Add new memblock region [@base,@base+@size) into @type. The new
region
* is allowed to overlap with existing ones - overlaps don't affect
already
* existing regions. @type is guaranteed to be minimal (all
neighbouring
* compatible regions are merged) after the addition.
*
* RETURNS:
* 0 on success, -errno on failure.
*/
IMO the function description is pretty straight-forward.
You need to differentiate the device-tree spec itself and Linux
implementation. memblock is something common to all architecture. It
does not mean it is something valid to do.
But let us wait for device tree guys feedback.
Cheers,
--
Julien Grall
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