Re: [PATCH v3 0/3] PCI: of: update endpoint ranges dynamically

[Andrea della Porta]

Hi Alex,

On 17:24 Thu 24 Sep     , Alex Elder wrote:
> A PCI endpoint bus is a devicetree construct that allows a PCI
> endpoint (function) to have sub-devices defined that are accessible
> in an SoC via the PCI endpoint's BARs.  Such a bus is represented as
> a devicetree sub-node for a PCI function having the name "pci-ep-bus".
> There can be one or more pci-ep-bus nodes.
> 
> A PCI function with a pci-ep-bus devicetree node must also define
> "#address-cells", "#size-cells", and "ranges" properties, to specify
> how endpoint bus addresses are translated to the PCI parent bus.
> 
> An endpoint bus address has three cells; the first indicates which of
> the function's BARs the address is associated with, and the other two
> specify a 64-bit (2 cell) offset within the BAR's region.
> 
> BAR base addresses are determined dynamically by the PCI enumeration
> process, so generally it's not possible to include them in a static
> devicetree file.  When this addressing scheme was introduced, this
> was not a problem because the devicetree content was generated
> dynamically--after booting--based on the information (including BAR
> addresses) available following PCI enumeration.
> 
> It is possible (and in some cases, necessary) to define the devicetree
> nodes that represent PCI devices ahead of time, in a statically-defined
> devicetree file.  In order to support the PCI endpoint bus model in this
> case it is necessary to dynamically update the static devicetree so that
> the BAR base addresses assigned during enumeration are reflected in the
> endpoint's "ranges" property.
> 
> This series implements that dynamic update, leveraging the same code
> used to create the "ranges" property when PCI_DYNAMIC_OF_NODES is
> enabled.  The first patch makes an argument to of_pci_get_addr_flags()
> optional.  The second patch separates the code that dynamically builds
> the property value into a helper function, and the last arranges for a
> statically-defined devicetree node for a PCI endpoint to have its
> "ranges" property updated (if it includes a "pci-ep-bus" sub-node)..
> 
> 					-Alex
> 
> Note: this series is built upon these patches:
>   https://lore.kernel.org/lkml/20260924150222.1179235-5-elder@xxxxxxxxxxxx/
> 
> The entire series (based on v7.3-rc4 and including those prerequisites)
> is available here:
>   https://github.com/riscstar/linux/tree/outgoing/dynamic_ranges-v3
> 
> Between version 2 and version 3:
> - The ranges property for a PCI endpoint with an existing devicetree node
>   is only updated if its ranges property has an empty value (i.e., it is
>   "ranges;", or is not defined)
> 
> Version 2 is available here:
>   https://lore.kernel.org/lkml/20260910021919.3421449-1-elder@xxxxxxxxxxxx/
> 
> Between version 1 and version 2:
> - Included the first patch (which was previously posted in a different
>   series)
> - Modified the last patch so the ranges property is updated only for
>   PCI endpoints having at least one "pci-ep-bus" node
> - Rebased on v7.3-rc2 (and the prerequisite series)
> 
> Version 1 is available here:
>   https://lore.kernel.org/lkml/20260813220717.1394644-1-elder@xxxxxxxxxxxx/
> 
> 
> Alex Elder (3):
>   PCI: of: make a flags argument optional
>   PCI: of: introduce of_pci_build_prop_ranges()
>   PCI: of: introduce of_pci_update_endpoint_node_ranges()
> 
>  drivers/pci/of.c          |  94 +++++++++++++++++++++++---
>  drivers/pci/of_property.c | 137 +++++++++++++++++++++++++-------------
>  drivers/pci/pci.h         |   1 +
>  3 files changed, 178 insertions(+), 54 deletions(-)
> 
> 
> base-commit: 6ba8359b84d69a07d508693551ed3f661d838e9f
> -- 
> 2.53.0
>

After a quick test, it seems that it's not working out of the
box on my RPi5. Let me investigate a bit to see what's wrong.

Many thanks,
Andrea