Re: [PATCH 11/16] of: property: Allow fw_devlink device-tree support for x86

Andy Shevchenko
2025-04-07T15:36:46Z

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@bootlin.com>

--
With Best Regards,
Andy Shevchenko