linux-kernel - Re: [PATCH 11/16] of: property: Allow fw

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Message-ID: <Z_Pw_MoPpVNwiEhc@smile.fi.intel.com>
Date: Mon, 7 Apr 2025 18:36:28 +0300
From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To: Herve Codina <herve.codina@...tlin.com>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	Danilo Krummrich <dakr@...nel.org>, Shawn Guo <shawnguo@...nel.org>,
	Sascha Hauer <s.hauer@...gutronix.de>,
	Pengutronix Kernel Team <kernel@...gutronix.de>,
	Fabio Estevam <festevam@...il.com>,
	Michael Turquette <mturquette@...libre.com>,
	Stephen Boyd <sboyd@...nel.org>, Andi Shyti <andi.shyti@...nel.org>,
	Wolfram Sang <wsa+renesas@...g-engineering.com>,
	Peter Rosin <peda@...ntia.se>,
	Derek Kiernan <derek.kiernan@....com>,
	Dragan Cvetic <dragan.cvetic@....com>,
	Arnd Bergmann <arnd@...db.de>, Rob Herring <robh@...nel.org>,
	Saravana Kannan <saravanak@...gle.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
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	Daniel Scally <djrscally@...il.com>,
	Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
	Sakari Ailus <sakari.ailus@...ux.intel.com>,
	Wolfram Sang <wsa@...nel.org>,
	Geert Uytterhoeven <geert+renesas@...der.be>,
	linux-kernel@...r.kernel.org, imx@...ts.linux.dev,
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	linux-pci@...r.kernel.org, linux-spi@...r.kernel.org,
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	Allan Nielsen <allan.nielsen@...rochip.com>,
	Horatiu Vultur <horatiu.vultur@...rochip.com>,
	Steen Hegelund <steen.hegelund@...rochip.com>,
	Luca Ceresoli <luca.ceresoli@...tlin.com>,
	Thomas Petazzoni <thomas.petazzoni@...tlin.com>
Subject: Re: [PATCH 11/16] of: property: Allow fw_devlink device-tree support
 for x86

On Mon, Apr 07, 2025 at 04:55:40PM +0200, Herve Codina wrote:
> PCI drivers can use a device-tree overlay to describe the hardware
> available on the PCI board. This is the case, for instance, of the
> LAN966x PCI device driver.
> 
> Adding some more nodes in the device-tree overlay adds some more
> consumer/supplier relationship between devices instantiated from this
> overlay.
> 
> Those fw_node consumer/supplier relationships are handled by fw_devlink
> and are created based on the device-tree parsing done by the
> of_fwnode_add_links() function.
> 
> Those consumer/supplier links are needed in order to ensure a correct PM
> runtime management and a correct removal order between devices.
> 
> For instance, without those links a supplier can be removed before its
> consumers is removed leading to all kind of issue if this consumer still
> want the use the already removed supplier.
> 
> The support for the usage of an overlay from a PCI driver has been added
> on x86 systems in commit 1f340724419ed ("PCI: of: Create device tree PCI
> host bridge node").
> 
> In the past, support for fw_devlink on x86 had been tried but this
> support has been removed in commit 4a48b66b3f52 ("of: property: Disable
> fw_devlink DT support for X86"). Indeed, this support was breaking some
> x86 systems such as OLPC system and the regression was reported in [0].
> 
> Instead of disabling this support for all x86 system, use a finer grain
> and disable this support only for the possible problematic subset of x86

> system mixing ACPI and device-tree at boot time (i.e. OLPC and CE4100).

This is incorrect, they never had ACPI to begin with. Also there is third
platform that are using DT on x86 core — SpreadTrum based phones.

And not sure about AMD stuff (Geode?).

> [0] https://lore.kernel.org/lkml/3c1f2473-92ad-bfc4-258e-a5a08ad73dd0@web.de/

Can you make this to be a Link tag?

Link: https://lore.kernel.org/lkml/3c1f2473-92ad-bfc4-258e-a5a08ad73dd0@web.de/ [0]

> Signed-off-by: Herve Codina <herve.codina@...tlin.com>

-- 
With Best Regards,
Andy Shevchenko