| Message ID | 20250507071315.394857-18-herve.codina@bootlin.com |
|---|---|
| State | New |
| Headers | show |
| Series | [v2,01/26] Revert "treewide: Fix probing of devices in DT overlays" | expand |
On Wed, May 07, 2025 at 09:12:59AM +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 are removed OR consumer > 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, a first approach > would be to use a finer grain and disable this support only for the > possible problematic subset of x86 systems (at least OLPC and CE4100). > > This first approach could still leads to issues. Indeed, the list of > possible problematic system and the way to identify them using Kconfig > symbols is not well defined and so some system can be missed leading to > kernel regressions on those missing systems. > > Use an other way and enable the support on x86 system only when this > support is needed by some specific feature. The usage of a device-tree > overlay by a PCI driver and thus the creation of PCI device-tree nodes > is a feature that needs it. > > Signed-off-by: Herve Codina <herve.codina@bootlin.com> > link: https://lore.kernel.org/lkml/3c1f2473-92ad-bfc4-258e-a5a08ad73dd0@web.de/ [0] Link: (mind capitalisation) Otherwise LGTM, FWIW, Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
diff --git a/drivers/of/property.c b/drivers/of/property.c index c1feb631e383..8b5cfee696e2 100644 --- a/drivers/of/property.c +++ b/drivers/of/property.c @@ -1605,7 +1605,7 @@ static int of_fwnode_add_links(struct fwnode_handle *fwnode) const struct property *p; struct device_node *con_np = to_of_node(fwnode); - if (IS_ENABLED(CONFIG_X86)) + if (IS_ENABLED(CONFIG_X86) && !IS_ENABLED(CONFIG_PCI_DYNAMIC_OF_NODES)) return 0; if (!con_np)
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, a first approach would be to use a finer grain and disable this support only for the possible problematic subset of x86 systems (at least OLPC and CE4100). This first approach could still leads to issues. Indeed, the list of possible problematic system and the way to identify them using Kconfig symbols is not well defined and so some system can be missed leading to kernel regressions on those missing systems. Use an other way and enable the support on x86 system only when this support is needed by some specific feature. The usage of a device-tree overlay by a PCI driver and thus the creation of PCI device-tree nodes is a feature that needs it. Signed-off-by: Herve Codina <herve.codina@bootlin.com> link: https://lore.kernel.org/lkml/3c1f2473-92ad-bfc4-258e-a5a08ad73dd0@web.de/ [0] --- drivers/of/property.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)