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

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Date:   Thu, 21 Sep 2023 07:20:46 -0500
From:   Rob Herring <robh@...nel.org>
To:     Andy Shevchenko <andriy.shevchenko@...el.com>
Cc:     Herve Codina <herve.codina@...tlin.com>,
        Jonathan Cameron <jonathan.cameron@...wei.com>,
        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

On Mon, Sep 18, 2023 at 2:17 AM Andy Shevchenko
<andriy.shevchenko@...el.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@...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.
>
> 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.

Rob