[PATCH v1 1/1] PCI: of: Propagate firmware node

[PATCH v1 1/1] PCI: of: Propagate firmware node

[Andy Shevchenko]

Propagate firmware node by using a specific API call, i.e. device_set_node().

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
---
 drivers/pci/of.c | 19 +++++++------------
 1 file changed, 7 insertions(+), 12 deletions(-)

diff --git a/drivers/pci/of.c b/drivers/pci/of.c
index 196834ed44fe..4bba00dfbfc5 100644
--- a/drivers/pci/of.c
+++ b/drivers/pci/of.c
@@ -18,19 +18,18 @@
 #ifdef CONFIG_PCI
 void pci_set_of_node(struct pci_dev *dev)
 {
+	struct device_node *node;
+
 	if (!dev->bus->dev.of_node)
 		return;
-	dev->dev.of_node = of_pci_find_child_device(dev->bus->dev.of_node,
-						    dev->devfn);
-	if (dev->dev.of_node)
-		dev->dev.fwnode = &dev->dev.of_node->fwnode;
+	node = of_pci_find_child_device(dev->bus->dev.of_node, dev->devfn);
+	device_set_node(&dev->dev, of_fwnode_handle(node));
 }
 
 void pci_release_of_node(struct pci_dev *dev)
 {
 	of_node_put(dev->dev.of_node);
-	dev->dev.of_node = NULL;
-	dev->dev.fwnode = NULL;
+	device_set_node(&dev->dev, NULL);
 }
 
 void pci_set_bus_of_node(struct pci_bus *bus)
@@ -45,17 +44,13 @@ void pci_set_bus_of_node(struct pci_bus *bus)
 			bus->self->external_facing = true;
 	}
 
-	bus->dev.of_node = node;
-
-	if (bus->dev.of_node)
-		bus->dev.fwnode = &bus->dev.of_node->fwnode;
+	device_set_node(&bus->dev, of_fwnode_handle(node));
 }
 
 void pci_release_bus_of_node(struct pci_bus *bus)
 {
 	of_node_put(bus->dev.of_node);
-	bus->dev.of_node = NULL;
-	bus->dev.fwnode = NULL;
+	device_set_node(&bus->dev, NULL);
 }
 
 struct device_node * __weak pcibios_get_phb_of_node(struct pci_bus *bus)
-- 
2.40.0.1.gaa8946217a0b

Re: [PATCH v1 1/1] PCI: of: Propagate firmware node

[Bjorn Helgaas]

On Wed, Apr 12, 2023 at 04:15:20PM +0300, Andy Shevchenko wrote:
> Propagate firmware node by using a specific API call, i.e. device_set_node().

Can you add a line or two about *why* we should do this, e.g., is this
headed toward some goal?  Is it a simplification that's 100%
equivalent (doesn't seem so, see below)?

Seems like there's an underlying long-term effort to unify things from
OF and ACPI, which seems like a good thing, but at the moment it's a
little confusing to follow.  For instance pci_set_of_node() seems like
it ought to be sort of analogous to pci_set_acpi_fwnode(), but they
look nothing alike.

> Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> ---
>  drivers/pci/of.c | 19 +++++++------------
>  1 file changed, 7 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/pci/of.c b/drivers/pci/of.c
> index 196834ed44fe..4bba00dfbfc5 100644
> --- a/drivers/pci/of.c
> +++ b/drivers/pci/of.c
> @@ -18,19 +18,18 @@
>  #ifdef CONFIG_PCI
>  void pci_set_of_node(struct pci_dev *dev)
>  {
> +	struct device_node *node;
> +
>  	if (!dev->bus->dev.of_node)
>  		return;
> -	dev->dev.of_node = of_pci_find_child_device(dev->bus->dev.of_node,
> -						    dev->devfn);
> -	if (dev->dev.of_node)
> -		dev->dev.fwnode = &dev->dev.of_node->fwnode;
> +	node = of_pci_find_child_device(dev->bus->dev.of_node, dev->devfn);
> +	device_set_node(&dev->dev, of_fwnode_handle(node));

This doesn't seem 100% equivalent.  If of_pci_find_child_device()
returns NULL, the previous code doesn't set dev->dev.fwnode, but the
new code does.

>  }
>  
>  void pci_release_of_node(struct pci_dev *dev)
>  {
>  	of_node_put(dev->dev.of_node);
> -	dev->dev.of_node = NULL;
> -	dev->dev.fwnode = NULL;
> +	device_set_node(&dev->dev, NULL);
>  }
>  
>  void pci_set_bus_of_node(struct pci_bus *bus)
> @@ -45,17 +44,13 @@ void pci_set_bus_of_node(struct pci_bus *bus)
>  			bus->self->external_facing = true;
>  	}
>  
> -	bus->dev.of_node = node;
> -
> -	if (bus->dev.of_node)
> -		bus->dev.fwnode = &bus->dev.of_node->fwnode;
> +	device_set_node(&bus->dev, of_fwnode_handle(node));
>  }
>  
>  void pci_release_bus_of_node(struct pci_bus *bus)
>  {
>  	of_node_put(bus->dev.of_node);
> -	bus->dev.of_node = NULL;
> -	bus->dev.fwnode = NULL;
> +	device_set_node(&bus->dev, NULL);
>  }
>  
>  struct device_node * __weak pcibios_get_phb_of_node(struct pci_bus *bus)
> -- 
> 2.40.0.1.gaa8946217a0b
> 

Re: [PATCH v1 1/1] PCI: of: Propagate firmware node

[Andy Shevchenko]

On Wed, Apr 12, 2023 at 11:02:53AM -0500, Bjorn Helgaas wrote:
> On Wed, Apr 12, 2023 at 04:15:20PM +0300, Andy Shevchenko wrote:
> > Propagate firmware node by using a specific API call, i.e. device_set_node().
> 
> Can you add a line or two about *why* we should do this, e.g., is this
> headed toward some goal?

Because dereferencing the fwnode in struct device is preventing us from
modifications of how fwnode looks like in the future.

> Is it a simplification that's 100%
> equivalent (doesn't seem so, see below)?

To me it's an equivalent, I'll explain below.

> Seems like there's an underlying long-term effort to unify things from
> OF and ACPI, which seems like a good thing, but at the moment it's a
> little confusing to follow.  For instance pci_set_of_node() seems like
> it ought to be sort of analogous to pci_set_acpi_fwnode(), but they
> look nothing alike.

Unification to some extent, but here is not a point of this change.

...

> > +	struct device_node *node;
> > +
> >  	if (!dev->bus->dev.of_node)
> >  		return;
> > -	dev->dev.of_node = of_pci_find_child_device(dev->bus->dev.of_node,
> > -						    dev->devfn);
> > -	if (dev->dev.of_node)
> > -		dev->dev.fwnode = &dev->dev.of_node->fwnode;
> > +	node = of_pci_find_child_device(dev->bus->dev.of_node, dev->devfn);
> > +	device_set_node(&dev->dev, of_fwnode_handle(node));
> 
> This doesn't seem 100% equivalent.  If of_pci_find_child_device()
> returns NULL, the previous code doesn't set dev->dev.fwnode, but the
> new code does.

Yes and this is not a problem. We create device with pci_alloc_dev() in both
callers of the pci_setup_device() and the field is NULL anyway. So, the last
condition there is a simple micro-optimisation.


-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v1 1/1] PCI: of: Propagate firmware node

[Bjorn Helgaas]

On Thu, Apr 13, 2023 at 07:00:26PM +0300, Andy Shevchenko wrote:
> On Wed, Apr 12, 2023 at 11:02:53AM -0500, Bjorn Helgaas wrote:
> > On Wed, Apr 12, 2023 at 04:15:20PM +0300, Andy Shevchenko wrote:
> > > Propagate firmware node by using a specific API call, i.e. device_set_node().
> > 
> > Can you add a line or two about *why* we should do this, e.g., is this
> > headed toward some goal?
> 
> Because dereferencing the fwnode in struct device is preventing us from
> modifications of how fwnode looks like in the future.

How do you want to express this in the commit log?  Something like
this?

  Insulate pci_set_of_node() and pci_set_bus_of_node() from possible
  changes to fwnode_handle implementation by using device_set_node()
  instead of open-coding dev->dev.fwnode assignments.

> > Is it a simplification that's 100%
> > equivalent (doesn't seem so, see below)?
> 
> To me it's an equivalent, I'll explain below.
> 
> > Seems like there's an underlying long-term effort to unify things from
> > OF and ACPI, which seems like a good thing, but at the moment it's a
> > little confusing to follow.  For instance pci_set_of_node() seems like
> > it ought to be sort of analogous to pci_set_acpi_fwnode(), but they
> > look nothing alike.
> 
> Unification to some extent, but here is not a point of this change.
> 
> ...
> 
> > > +	struct device_node *node;
> > > +
> > >  	if (!dev->bus->dev.of_node)
> > >  		return;
> > > -	dev->dev.of_node = of_pci_find_child_device(dev->bus->dev.of_node,
> > > -						    dev->devfn);
> > > -	if (dev->dev.of_node)
> > > -		dev->dev.fwnode = &dev->dev.of_node->fwnode;
> > > +	node = of_pci_find_child_device(dev->bus->dev.of_node, dev->devfn);
> > > +	device_set_node(&dev->dev, of_fwnode_handle(node));
> > 
> > This doesn't seem 100% equivalent.  If of_pci_find_child_device()
> > returns NULL, the previous code doesn't set dev->dev.fwnode, but the
> > new code does.
> 
> Yes and this is not a problem. We create device with pci_alloc_dev() in both
> callers of the pci_setup_device() and the field is NULL anyway. So, the last
> condition there is a simple micro-optimisation.

OK, makes sense, thanks.

Bjorn

Re: [PATCH v1 1/1] PCI: of: Propagate firmware node

[Andy Shevchenko]

On Fri, Apr 14, 2023 at 01:55:45PM -0500, Bjorn Helgaas wrote:
> On Thu, Apr 13, 2023 at 07:00:26PM +0300, Andy Shevchenko wrote:
> > On Wed, Apr 12, 2023 at 11:02:53AM -0500, Bjorn Helgaas wrote:
> > > On Wed, Apr 12, 2023 at 04:15:20PM +0300, Andy Shevchenko wrote:

...

> > > > Propagate firmware node by using a specific API call, i.e. device_set_node().
> > > 
> > > Can you add a line or two about *why* we should do this, e.g., is this
> > > headed toward some goal?
> > 
> > Because dereferencing the fwnode in struct device is preventing us from
> > modifications of how fwnode looks like in the future.
> 
> How do you want to express this in the commit log?  Something like
> this?
> 
>   Insulate pci_set_of_node() and pci_set_bus_of_node() from possible
>   changes to fwnode_handle implementation by using device_set_node()
>   instead of open-coding dev->dev.fwnode assignments.

Sounds good to me, thanks for the draft. I will do it in v2 this way.

-- 
With Best Regards,
Andy Shevchenko