On Thu, 9 Dec 2021 at 10:58, Arnd Bergmann [off-list ref] wrote:

On Thu, Dec 9, 2021 at 9:49 AM qinjian[覃健] [off-list ref] wrote:

quoted

quoted

On Tue, Dec 7, 2021 at 8:21 AM qinjian[覃健] [off-list ref] wrote:

quoted

quoted

quoted

@@ -152,6 +152,7 @@ textofs-$(CONFIG_ARCH_MSM8X60) := 0x00208000
 textofs-$(CONFIG_ARCH_MSM8960) := 0x00208000
 textofs-$(CONFIG_ARCH_MESON) := 0x00208000
 textofs-$(CONFIG_ARCH_AXXIA) := 0x00308000
+textofs-$(CONFIG_ARCH_SUNPLUS) := 0x00308000

What is this needed for? If it boots without this line, better avoid
adding it, because
it will increase the kernel size for everyone else (unless they also enable
AXXIA).

SP7021 reserved the 1st 1MB memory for ARM926@P-Chip using,
The 2nd 1MB memory for IOP device and the 3rd 1MB memory for bootloader.
I'll add these comments at next commit.

I think you can just remove the memory from the system memory map in the
device tree and pretend it only starts after the bootloader. It's been a while
since I looked at this though, so I could be misremembering what the minimum
boundaries are for doing this.

I have test following 3 methods:

Right, I was thinking of the third method here, which has the advantage of
not requiring the same odd base address for all other platforms, this
is important to us.
I don't see what the problem is with it in your example, does that mean you
have a little less usable memory, or that something fails to work right? I don't
know what the requirements are for memreserve.

Adding a few more people to Cc, maybe they have ideas about how this
was solved elsewhere.

The phys2virt patching now assumes a granularity of 2 MiB. This means
that by removing 3 MiB at the start of DRAM, you lose 1 MIB of usable
memory unless you find a way to memremap() it directly.

So I think a combination of the two approaches might work here
- remove 2 MiB from the the /memory node.
- add 1 MiB to the text offset instead of 3 MiB.

Note that this is a compromise, and still not our preferred approach.
It would be far better to move these reserved regions to the end of
DRAM instead.

quoted

1. current patch
DT:
        memory {
                reg = <0x00000000 0x20000000>; /* 512MB */
        };

        reserved-memory {
                #address-cells = <1>;
                #size-cells = <1>;
                ranges;

                iop_reserve: iop_device {
                        no-map;
                        reg = <0x00100000 0x00100000>;
                };
                a926_reserve: a926_memory {
                        no-map;
                        reg = <0x00000000 0x00100000>;
                };
        };
arch/arm/Makefile:
        textofs-$(CONFIG_ARCH_SUNPLUS) := 0x00308000

bootlog & meminfo :
[    0.000000] Zone ranges:
[    0.000000]   Normal   [mem 0x0000000000000000-0x000000001fffffff]
[    0.000000] Movable zone start for each node
[    0.000000] Early memory node ranges
[    0.000000]   node   0: [mem 0x0000000000000000-0x00000000001fffff]
[    0.000000]   node   0: [mem 0x0000000000200000-0x000000001fffffff]
[    0.000000] Initmem setup node 0 [mem 0x0000000000000000-0x000000001fffffff]

~ # cat /proc/meminfo
MemTotal:         514008 kB
MemFree:          491960 kB
MemAvailable:     488608 kB



2. DT same as case 1, but no modify @ arch/arm/Makefile

bootlog & meminfo :
[    0.000000] OF: fdt: Reserved memory: failed to reserve memory for node 'iop_device': base 0x00100000, size 1 MiB
[    0.000000] OF: fdt: Reserved memory: failed to reserve memory for node 'a926_memory': base 0x00000000, size 1 MiB
...
[    0.000000] Zone ranges:
[    0.000000]   Normal   [mem 0x0000000000000000-0x000000001fffffff]
[    0.000000] Movable zone start for each node
[    0.000000] Early memory node ranges
[    0.000000]   node   0: [mem 0x0000000000000000-0x000000001fffffff]
[    0.000000] Initmem setup node 0 [mem 0x0000000000000000-0x000000001fffffff]

~ # cat /proc/meminfo
MemTotal:         516056 kB
MemFree:          493928 kB
MemAvailable:     490572 kB



3. DT:
        memory {
                reg = <0x00300000 0x1FD00000>; /* 512 - 3 MB */
        };
no modify @ arch/arm/Makefile

bootlog & meminfo :
[    0.000000] Zone ranges:
[    0.000000]   Normal   [mem 0x0000000000400000-0x000000001fffffff]
[    0.000000] Movable zone start for each node
[    0.000000] Early memory node ranges
[    0.000000]   node   0: [mem 0x0000000000400000-0x000000001fffffff]
[    0.000000] Initmem setup node 0 [mem 0x0000000000400000-0x000000001fffffff]

~ # cat /proc/meminfo
MemTotal:         511964 kB
MemFree:          489636 kB
MemAvailable:     486292 kB



I think method 1 should be correct (compare method 2) & better (compare method 3).