Re: [PATCH 3/4] ARM: dts: BCM5301X: Add DT for ASUS RT-AC3200

From: Florian Fainelli
Date: Wed Apr 17 2024 - 12:47:23 EST



On 4/17/2024 6:23 AM, Krzysztof Kozlowski wrote:
On 17/04/2024 05:15, Florian Fainelli wrote:


On 4/15/2024 2:10 AM, Arınç ÜNAL wrote:
On 15.04.2024 10:57, Krzysztof Kozlowski wrote:
On 14/04/2024 22:21, Arınç ÜNAL wrote:
NVRAM is described as both flash device partition and memory mapped
NVMEM.
This platform stores NVRAM on flash but makes it also memory accessible.

As device partitions are described in board DTS, the nvram node must
also

Sorry, but we do not talk about partitions. Partitions are indeed board
property. But the piece of hardware, so NVMEM, is provided by SoC.

be defined there as its address and size will be different by board.
It has
been widely described on at least bcm4709 and bcm47094 SoC board DTS
files
here.

These not proper arguments. What you are saying here is that SoC does no
have nvram at address 0x1c08000. Instead you are saying there some sort
of bus going out of SoC to the board and on the board physically there
is some NVRAM sort of memory attached to this bus.

Yes that is the case. NVRAM is stored on a partition on the flash. On the
Broadcom NorthStar platform, the NAND flash base is 0x1c000000, the NOR
flash base is 0x1e000000.

For the board in this patch, the flash is a NAND flash. The NVRAM partition
starts at address 0x00080000. Therefore, the NVRAM component's address is
0x1c080000.

Because the flash is memory mapped into the CPU's address space, a
separate node was defined since it is not part of the "soc" node which
describes the bridge that connects all of the peripherals.

Whether we should create an additional bus node which describes the
bridge being used to access the flash devices using the MMIO windows is
debatable. Rafal, what do you think?

Sorry guys, I don't get. I don't know the addresses neither the names
like Broadcom Northstar, so this does not clarify me at all.

Northstar is just a code name for the BCM5301X SoC family. The SoC memory map looks like this:

0x0000_0000 ~ 0x07FF_FFFF - DDR
0x0800_0000 ~ 0x0FFF_FFFF - PCIe0
0x1800_0000 ~ 0x180F_FFFF - Core registers (that is chipcommon-a-bus@18000000 and axi@18000000 in DT)
0x1810_0000 ~ 0x181F_FFFF - IDM registers
0x1900_0000 ~ 0x190F_FFFF - ARMCore registers (that is mpcore-bus@19000000 in DT)
0x1C00_0000 ~ 0x1DFF_FFFF - NAND flash
0x1E00_0000 ~ 0x1FFF_FFFF - SPI-NOR flash
0x4000_0000 ~ 0x47FF_FFFF - PCIe1
0x4800_0000 ~ 0x4FFF_FFFF - PCIe2
0x8000_0000 ~ 0xBFFF_FFFF - DDR

From the system diagram the CPU has 3 AXI ports to the NIC301 AXI fabric, which itself has separate AXI ports to the NAND and SPI-NOR MMIO interface and then different AXI and APB ports to various other peripherals.

This information was not accessible to Rafal at the time, so it would not have been reasonable to expect from him to know such details.


Please answer the simple questions:
1. Is NAND flash part of SoC?
2. If not, is NAND flash provided by Broadcom or anyone else?

The NAND flash is external to the SoC it is not manufactured by Broadcom we have boards with Spansion, Micron, Macronix, Toshiba flashes etc.
--
Florian

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