Hi Folks,
I have a question regarding "reserved-memory". I am using an Arm Juno
platform which has a chunk of ram in its fpga. I intend to make this
memory as reserved so that it can be shared between various devices
for passing framebuffer.
My dts looks like the following:-
/ {
.... // some nodes
tlx@60000000 {
compatible = "simple-bus";
...
juno_wrapper {
... /* here we have all the nodes */
/* corresponding to the devices in the fpga */
memory@d000000 {
device_type = "memory";
reg = <0x00 0x60000000 0x00 0x8000000>;
};
reserved-memory {
#address-cells = <0x01>;
#size-cells = <0x01>;
ranges;
framebuffer@d000000 {
compatible = "shared-dma-pool";
linux,cma-default;
reusable;
reg = <0x00 0x60000000 0x00 0x8000000>;
phandle = <0x44>;
};
};
...
}
}
...
}
Note that the depth of the "reserved-memory" node is 3.
Refer __fdt_scan_reserved_mem() :-
if (!found && depth == 1 && strcmp(uname, "reserved-memory") == 0) {
if (__reserved_mem_check_root(node) != 0) {
pr_err("Reserved memory: unsupported node
format, ignoring\n");
/* break scan */
return 1;
}
found = 1;
/* scan next node */
return 0;
}
It expects the "reserved-memory" node to be at depth == 1 and so it
does not probe it in our case.
Niether from the
Documentation/devicetree/bindings/reserved-memory/reserved-memory.txt
nor from commit - e8d9d1f5485b52ec3c4d7af839e6914438f6c285,
I could understand the reason for such restriction.
So, I seek the community's advice as to whether I should fix up
__fdt_scan_reserved_mem() so as to do away with the restriction or
put the "reserved-memory" node outside of 'tlx@60000000' (which looks
logically incorrect as the memory is on the fpga platform).
Thanks,
Ayan
