Date: Wed, 17 Apr 2024 09:47:05 -0700
From: Florian Fainelli <florian.fainelli@...adcom.com>
To: Krzysztof Kozlowski <krzk@...nel.org>,
 Florian Fainelli <florian.fainelli@...adcom.com>,
 Arınç ÜNAL <arinc.unal@...nc9.com>,
 Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
 Conor Dooley <conor+dt@...nel.org>, Hauke Mehrtens <hauke@...ke-m.de>,
 Rafal Milecki <zajec5@...il.com>,
 Broadcom internal kernel review list <bcm-kernel-feedback-list@...adcom.com>
Cc: Tom Brautaset <tbrautaset@...il.com>, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 3/4] ARM: dts: BCM5301X: Add DT for ASUS RT-AC3200



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@...00000 and axi@...00000 in DT)
0x1810_0000 ~ 0x181F_FFFF - IDM registers
0x1900_0000 ~ 0x190F_FFFF - ARMCore registers (that is 
mpcore-bus@...00000 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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