Le Tue, 3 May 2022 09:12:06 -0500,
Rob Herring <robh@xxxxxxxxxx> a écrit :
> On Wed, Apr 27, 2022 at 11:45:01AM +0200, Clément Léger wrote:
> > In order to apply overlays to PCI device nodes, the nodes must first
> > exist. This commit add support to populate a skeleton tree for PCI bus
> > and devices. These nodes can then be used by drivers to apply overlays.
> >
>
> While I implemented this creating the nodes as the PCI devices are
> created, I think probably we're going to want to create the device node
> and any needed parent nodes on demand. Otherwise, just turning on
> CONFIG_OF could break platforms.
Ok, so this creation would potentially be done on request from some PCI
driver that want to apply it's overlay on the tree. Should I actually
add some function such as of_pci_apply_overlay() which would create the
PCI node tree if not present and apply the overlay to the of_node that
is associated to the PCIe device ?
>
> One potential issue is that fwnode assumes there is either a DT node or
> ACPI node. With this, we have the potential for both. I'm not sure how
> much that's going to be an issue.
Not sure either but that's better not to play with that.
>
> > Co-developed-by: Rob Herring <robh@xxxxxxxxxx>
> > Signed-off-by: Rob Herring <robh@xxxxxxxxxx>
> > Signed-off-by: Clément Léger <clement.leger@xxxxxxxxxxx>
> > ---
> > drivers/pci/of.c | 184 +++++++++++++++++++++++++++++++++++++++++++++++
> > 1 file changed, 184 insertions(+)
> >
> > diff --git a/drivers/pci/of.c b/drivers/pci/of.c
> > index cb2e8351c2cc..f2325708726e 100644
> > --- a/drivers/pci/of.c
> > +++ b/drivers/pci/of.c
> > @@ -16,12 +16,194 @@
> > #include "pci.h"
> >
> > #ifdef CONFIG_PCI
> > +static int of_pci_add_property(struct of_changeset *ocs, struct device_node *np,
> > + const char *name, const void *value, int length)
>
> Nothing really PCI specific about this function.
>
> The kernel support for creating nodes and properties is pretty poor. We
> should improve it with functions like this (in drivers/of/). Maybe the
> changeset part should be separate though. We have some cases of creating
> properties or nodes already, and whatever new APIs we make those
> cases should be able to use them. And if they are converted, then it can
> be merged sooner rather than when all the PCI parts are ready.
Ok, so this will be done as a first separate series to add property
creation then.
> > +
> > +static int of_pci_add_cells_props(struct device_node *node,
> > + struct of_changeset *cs, int n_addr_cells,
> > + int n_size_cells)
> > +{
> > + __be32 val;
> > + int ret;
> > +
> > + ret = of_pci_add_property(cs, node, "ranges", NULL, 0);
>
> The host bridge node is going to need to fill in 'ranges'. Empty ranges
> is not valid when there's a change in number of cells.
Ok, wasn't aware of that. If I understand, I'll need to obtain the
range of PCI addresses that are behind the bridge to fill in this
ranges property right ?
>
> The root node also will need "#address-cells" and "#size-cells".
>
Ok.
--
Clément Léger,
Embedded Linux and Kernel engineer at Bootlin
https://bootlin.com
