linux-kernel - Re: [PATCH V13 0/5] Generate device tree node for pci devices

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Date:   Fri, 15 Sep 2023 19:30:08 +0200
From:   Herve Codina <herve.codina@...tlin.com>
To:     Andy Shevchenko <andriy.shevchenko@...el.com>
Cc:     Rob Herring <robh@...nel.org>, Lizhi Hou <lizhi.hou@....com>,
        Andrew Lunn <andrew@...n.ch>, linux-pci@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        max.zhen@....com, sonal.santan@....com,
        stefano.stabellini@...inx.com
Subject: Re: [PATCH V13 0/5] Generate device tree node for pci devices

Hi Andy,

On Wed, 13 Sep 2023 14:17:30 +0300
Andy Shevchenko <andriy.shevchenko@...el.com> wrote:

> On Tue, Sep 12, 2023 at 02:12:04PM -0500, Rob Herring wrote:
> > On Mon, Sep 11, 2023 at 3:37 PM Andy Shevchenko
> > <andriy.shevchenko@...el.com> wrote:  
> > > On Tue, Aug 15, 2023 at 10:19:55AM -0700, Lizhi Hou wrote:  
> 
> ...
> 
> > > Can you point out to the ACPI excerpt(s) of the description of anything related
> > > to the device(s) in question?  
> > 
> > I don't understand what you are asking for.  
> 
> Through the email thread it was mentioned that this series was tested on the
> ACPI enabled platform, Jonathan (IIRC) asked why do we need to have a shadow
> DT for the something that ACPI already describes. That's why I'm trying to
> understand if it's the case. and if so, how can we improve the approach.
> 

Patches from Frank Rowand series [1] are needed to create an of_root_node if a DT
was not provided by the firmware, bootloader, etc that run the kernel.

[1]: https://lore.kernel.org/lkml/20220624034327.2542112-1-frowand.list@gmail.com/

Current Lizhi's series creates nodes from the PCI host node during the PCI
enumeration. It creates PCI-PCI bridge and PCI device nodes.

I use these series on an ACPI system.

I need one more missing component: the node related to the PCI host bridge
This was the purpose of Clement's work. This work was not sent upstream yet and I
am working on it in order to have a full tree from the of_root to the PCI device
ie:
 of_root                  <-- Frank Rowand series 
   + of_host_pci_bridge   <-- Clement's work
       + pci_bridge       <-- Current Lizhi series
           + pci_bridge   <-- Current Lizhi series
            ...
             + pci_dev    <-- Current Lizhi series

Hope that this status helped.

Regards,
Hervé

-- 
Hervé Codina, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com