linux-kernel - Re: [PATCH v6 1/7] dt-bindings: reset: microchip,rst: Allow to replace cpu-syscon by an additional reg item

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Message-ID: <20241001180621.76e497d0@bootlin.com>
Date: Tue, 1 Oct 2024 18:06:21 +0200
From: Herve Codina <herve.codina@...tlin.com>
To: Krzysztof Kozlowski <krzk@...nel.org>
Cc: Geert Uytterhoeven <geert@...ux-m68k.org>, Andy Shevchenko
 <andy.shevchenko@...il.com>, Simon Horman <horms@...nel.org>, Lee Jones
 <lee@...nel.org>, Arnd Bergmann <arnd@...db.de>, Derek Kiernan
 <derek.kiernan@....com>, Dragan Cvetic <dragan.cvetic@....com>, Greg
 Kroah-Hartman <gregkh@...uxfoundation.org>, Bjorn Helgaas
 <bhelgaas@...gle.com>, Philipp Zabel <p.zabel@...gutronix.de>, Lars Povlsen
 <lars.povlsen@...rochip.com>, Steen Hegelund
 <Steen.Hegelund@...rochip.com>, Daniel Machon
 <daniel.machon@...rochip.com>, UNGLinuxDriver@...rochip.com, Rob Herring
 <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
 <conor+dt@...nel.org>, Saravana Kannan <saravanak@...gle.com>, "David S.
 Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, Jakub
 Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, Horatiu Vultur
 <horatiu.vultur@...rochip.com>, Andrew Lunn <andrew@...n.ch>,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
 netdev@...r.kernel.org, linux-pci@...r.kernel.org,
 linux-arm-kernel@...ts.infradead.org, Allan Nielsen
 <allan.nielsen@...rochip.com>, Luca Ceresoli <luca.ceresoli@...tlin.com>,
 Thomas Petazzoni <thomas.petazzoni@...tlin.com>
Subject: Re: [PATCH v6 1/7] dt-bindings: reset: microchip,rst: Allow to
 replace cpu-syscon by an additional reg item

Hi Krystoff,

On Tue, 1 Oct 2024 08:43:23 +0200
Krzysztof Kozlowski <krzk@...nel.org> wrote:

> On Mon, Sep 30, 2024 at 02:15:41PM +0200, Herve Codina wrote:
> > In the LAN966x PCI device use case, syscon cannot be used as syscon
> > devices do not support removal [1]. A syscon device is a core "system"
> > device and not a device available in some addon boards and so, it is not
> > supposed to be removed.  
> 
> That's not accurate. syscon is our own, Linux term which means also
> anything exposing set of registers.
> 
> If you need to unload syscons, implement it. syscon is the same resource
> as all others so should be handled same way.
> 
> > 
> > In order to remove the syscon device usage, allow the reset controller
> > to have a direct access to the address range it needs to use.  
> 
> So you map same address twice? That's not good, because you have no
> locking over concurrent register accesses.
> 

I will remove this patch and keep using the syscon node in the next
iteration.

Best regards,
Hervé