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

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Message-ID: <48b2e0fd-4d7f-4bb6-aadd-804847e3250c@kernel.org>
Date: Wed, 17 Apr 2024 15:23:19 +0200
From: Krzysztof Kozlowski <krzk@...nel.org>
To: 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>, Florian Fainelli <f.fainelli@...il.com>,
 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 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.

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

Best regards,
Krzysztof