linux-kernel - Re: [PATCH 08/11] misc: rp1: RaspberryPi RP1 misc driver

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Message-ID: <39735704-ae94-4ff8-bf4d-d2638b046c8e@kernel.org>
Date: Tue, 3 Sep 2024 20:27:14 +0200
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Andrea della Porta <andrea.porta@...e.com>
Cc: Michael Turquette <mturquette@...libre.com>,
 Stephen Boyd <sboyd@...nel.org>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
 <conor+dt@...nel.org>, Florian Fainelli <florian.fainelli@...adcom.com>,
 Broadcom internal kernel review list
 <bcm-kernel-feedback-list@...adcom.com>,
 Linus Walleij <linus.walleij@...aro.org>,
 Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>,
 Derek Kiernan <derek.kiernan@....com>, Dragan Cvetic
 <dragan.cvetic@....com>, Arnd Bergmann <arnd@...db.de>,
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 Nicolas Ferre <nicolas.ferre@...rochip.com>,
 Claudiu Beznea <claudiu.beznea@...on.dev>,
 "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
 Saravana Kannan <saravanak@...gle.com>, Bjorn Helgaas <bhelgaas@...gle.com>,
 linux-clk@...r.kernel.org, devicetree@...r.kernel.org,
 linux-rpi-kernel@...ts.infradead.org, linux-arm-kernel@...ts.infradead.org,
 linux-kernel@...r.kernel.org, linux-gpio@...r.kernel.org,
 netdev@...r.kernel.org, linux-pci@...r.kernel.org,
 linux-arch@...r.kernel.org, Lee Jones <lee@...nel.org>,
 Andrew Lunn <andrew@...n.ch>, Stefan Wahren <wahrenst@....net>
Subject: Re: [PATCH 08/11] misc: rp1: RaspberryPi RP1 misc driver

On 03/09/2024 17:15, Andrea della Porta wrote:
>>>>> +
>>>>> +				rp1_clocks: clocks@...0018000 {
>>>>
>>>> Why do you mix MMIO with non-MMIO nodes? This really does not look
>>>> correct.
>>>>
>>>
>>> Right. This is already under discussion here:
>>> https://lore.kernel.org/all/ZtBzis5CzQMm8loh@apocalypse/
>>>
>>> IIUC you proposed to instantiate the non-MMIO nodes (the three clocks) by
>>> using CLK_OF_DECLARE.
>>
>> Depends. Where are these clocks? Naming suggests they might not be even
>> part of this device. But if these are part of the device, then why this
>> is not a clock controller (if they are controllable) or even removed
>> (because we do not represent internal clock tree in DTS).
> 
> xosc is a crystal connected to the oscillator input of the RP1, so I would
> consider it an external fixed-clock. If we were in the entire dts, I would have
> put it in root under /clocks node, but here we're in the dtbo so I'm not sure
> where else should I put it.

But physically, on which PCB, where is this clock located?

> 
> Regarding pclk and hclk, I'm still trying to understand where they come from.
> If they are external clocks (since they are fixed-clock too), they should be
> in the same node as xosc. CLK_OF_DECLARE does not seem to fit here because

There is no such node as "/clocks" so do not focus on that. That's just
placeholder but useless and it is inconsistent with other cases (e.g.
regulators).

If this is external oscillator then it is not part of RP1 and you cannot
put it inside just to satisfy your drivers.

> there's no special management of these clocks, so no new clock definition is
> needed.

> If they are internal tree, I cannot simply get rid of them because rp1_eth node
> references these two clocks (see clocks property), so they must be decalred 
> somewhere. Any hint about this?.
> 

Describe the hardware. Show the diagram or schematics where is which device.

Best regards,
Krzysztof