How to know physical memory address range

For Developers
1

Hi,

I have a sample with 1GB RAM. I want to know its physical memory address range. I checked memory node of device tree. Does it mean the address range is 0x0--0x3f ff ff ff?

root@OpenWRT:/sys/firmware/devicetree/base/memory# hexdump -C reg 
00000000  00 00 00 00 40 00 00 00  00 00 00 00 40 00 00 00  |....@.......@...|
00000010

If so, it seems not make sense. According to its dts file [1], node "reserved-memory" shows the physical memory address from 0x40000000. How do I understand this? Thank you!

reserved-memory {
	#ifdef __IPQ_MEM_PROFILE_256_MB__
......
......
#else

/*                 512MB/1GB Profiles
	 * +==========+==============+=========================+
	 * |          |              |                         |
	 * |  Region  | Start Offset |          Size           |
	 * |          |              |                         |
	 * +----------+--------------+-------------------------+
	 * |    NSS   |  0x40000000  |          16MB           |
	 * +----------+--------------+-------------------------+
	 * |   Linux  |  0x41000000  | Depends on total memory |
	 * +----------+--------------+-------------------------+
	 * |   uboot  |  0x4A600000  |           4MB           |
	 * +----------+--------------+-------------------------+
	 * |    SBL   |  0x4AA00000  |           1MB           |
	 * +----------+--------------+-------------------------+
	 * |   smem   |  0x4AB00000  |           1MB           |
	 * +----------+--------------+-------------------------+
	 * |    TZ    |  0x4AC00000  |           4MB           |
	 * +----------+--------------+-------------------------+
	 * |    Q6    |              |                         |
	 * |   code/  |  0x4B000000  |          20MB           |
	 * |   data   |              |                         |
	 * +----------+--------------+-------------------------+
	 * |  IPQ5018 |              |                         |
	 * |   data   |  0x4C400000  |          14MB           |
	 * +----------+--------------+-------------------------+
	 * |  IPQ5018 |              |                         |
	 * |  M3 Dump |  0x4D200000  |           1MB           |
	 * +----------+--------------+-------------------------+
	 * |  IPQ5018 |              |                         |
	 * |   QDSS   |  0x4D300000  |           1MB           |
	 * +----------+--------------+-------------------------+
	 * |  IPQ5018 |              |                         |
	 * |  Caldb   |  0x4D400000  |           2MB           |
	 * +----------+--------------+-------------------------+
	 * | QCN6122_1|              |                         |
	 * |   data   |  0x4D600000  |          16MB           |
	 * +----------+--------------+-------------------------+
	 * | QCN6122_1|              |                         |
	 * |  M3 Dump |  0x4E600000  |           1MB           |
	 * +----------+--------------+-------------------------+
	 * | QCN6122_1|              |                         |
	 * |   QDSS   |  0x4E700000  |           1MB           |
	 * +----------+--------------+-------------------------+
	 * | QCN6122_1|              |                         |
	 * |  Caldb   |  0x4E800000  |           5MB           |
	 * +----------+--------------+-------------------------+
	 * | QCN6122_2|              |                         |
	 * |   data   |  0x4ED00000  |          16MB           |
	 * +----------+--------------+-------------------------+
	 * | QCN6122_2|              |                         |
	 * |  M3 Dump |  0x4FD00000  |           1MB           |
	 * +----------+--------------+-------------------------+
	 * | QCN6122_2|              |                         |
	 * |   QDSS   |  0x4FE00000  |           1MB           |
	 * +----------+--------------+-------------------------+
	 * | QCN6122_2|              |                         |
	 * |  Caldb   |  0x4FF00000  |           5MB           |
	 * +----------+--------------+-------------------------+
	 * |                                                   |
	 * |            Rest of the memory for Linux           |
	 * |                                                   |
	 * +===================================================+
	 */
		q6_mem_regions: q6_mem_regions@4B000000 {
			no-map;
			reg = <0x0 0x4B000000 0x0 0x5400000>;
		};

		q6_code_data: q6_code_data@4B000000 {
			no-map;
			reg = <0x0 0x4B000000 0x0 01400000>;
		};

[1]https://source.codeaurora.org/quic/qsdk/oss/kernel/linux-msm/tree/arch/arm64/boot/dts/qcom/qcom-ipq5018-mp03.5-c1.dts?h=11.4.0.5

2

That means that the DRAM is mapped to address 0x40000000, this is pretty common for IPQ807x/60xx/50xx.

So you can access the DRAM like any other memory-mapped IO, just read and write to it.

3

So do you mean it's VM instead of physical memory? On IPQ806x, it seems that 0x40000000 is also physical memory address. Below output is from my R7800 whose SoC is IPQ806x.

root@OpenWrt:/sys/firmware/devicetree/base/memory# hexdump -C reg 
00000000  40 00 00 00 20 00 00 00                           |@... ...|
00000008
4

Here is how I translate the output of "hexdump -C reg":

The first 4 bytes is physical start address, the second 4 bytes is the size.

Is this correct? Actually, I don't know why there are the third and fourth 4 bytes on IPQ50xx. Why are they different between IPQ806x and IPQ50xx.

5

Its physical memory its just that the CPU maps its start at that address.

The format of the DT node depends on #address-cells and #size-cells properties.
For most platforms memory uses value 2 for both, meaning you provide 64 bit values instead of the default 32 bit.
So:
reg = <ADDR_HI_32_BITS ADDR_LO_32_BITS SIZE_HI_32_BITS SIZE_LO_32_BITS>;

6

Oh, yeah. You are right. I made such stupid mistake that I was not aware of the 64bit address. I used trace32 and confirm the NSS firmware is loaded into the address 0x40000000 on IPQ50xx.

ipq50xx-phy-memory
ipq50xx-phy-memory1896×695 89.2 KB

7

Oh, you got the Lauterbach JTAG?
I am looking into getting it due to working more and more on stuff that is getting hard to debug via printing

8

Yes, it's very useful for me to study and debug.

9

Is the price something you can share?

10

It's from my company. I don't know the price. But I guess it's about at least 6000$ for ARMv8.

11

Ok, then OpenOCD will be good as well for the start.
Thanks

12

Would you give me a reminder if you figure out how to use OpenOCD? I may use it when I am OOO. :grinning:Thanks.

13

Sure, I even got an an interface for it somewhere