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Date:   Thu, 21 Sep 2023 15:26:43 +0200
From:   Herve Codina <herve.codina@bootlin.com>
To:     Rob Herring <robh@kernel.org>
Cc:     Andy Shevchenko <andriy.shevchenko@intel.com>,
        Jonathan Cameron <jonathan.cameron@huawei.com>,
        Lizhi Hou <lizhi.hou@amd.com>, Andrew Lunn <andrew@lunn.ch>,
        linux-pci@vger.kernel.org, devicetree@vger.kernel.org,
        linux-kernel@vger.kernel.org, max.zhen@amd.com,
        sonal.santan@amd.com, stefano.stabellini@xilinx.com,
        Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Subject: Re: [PATCH V13 0/5] Generate device tree node for pci devices
Message-ID: <20230921152611.19e07907@bootlin.com>
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On Thu, 21 Sep 2023 07:20:46 -0500
Rob Herring <robh@kernel.org> wrote:

> On Mon, Sep 18, 2023 at 2:17 AM Andy Shevchenko
> <andriy.shevchenko@intel.com> wrote:
> >
> > On Fri, Sep 15, 2023 at 07:30:08PM +0200, Herve Codina wrote:  
> > > On Wed, 13 Sep 2023 14:17:30 +0300
> > > Andy Shevchenko <andriy.shevchenko@intel.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@intel.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.  
> >
> > Thanks for the explanation! I suppose it's better to have three series combined
> > into one and being sent with a better cover letter to explain all this.  
> 
> You can go back (years now) and see that. I asked for this to be split
> up into manageable chunks and not solve multiple problems at once. No
> point in trying to do DT on top of ACPI if DT on top of DT doesn't
> work first.

I agree.

Hervé

> 
> Rob


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