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

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Date:   Mon, 18 Sep 2023 11:54:10 +0100
From:   Jonathan Cameron <Jonathan.Cameron@...wei.com>
To:     Andy Shevchenko <andriy.shevchenko@...el.com>
CC:     Herve Codina <herve.codina@...tlin.com>,
        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

On Mon, 18 Sep 2023 10:17:26 +0300
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. Also it
> might make sense (in my opinion) to Cc Jonathan (I did it here). Sorry, Jonathan,
> if you are not wanting this.
> 
I'm lurking anyway via linux-pci :)

Indeed very interested in this.  I'm carrying a local copy of Clement's series but
more than happy if Herve gets that bit ready for upstream.

I think we are still some way from this all working for a non trivial PCI card
on an ACPI system though.  Maybe I'm wrong and the rest will turn out to be easy!

Jonathan