linux-kernel - Re: [PATCH v2 05/13] PCI: endpoint: Assign PCI domain number for endpoint controllers

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Message-ID: <20240718150103.GA2499@thinkpad>
Date: Thu, 18 Jul 2024 20:31:03 +0530
From: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To: Konrad Dybcio <konrad.dybcio@...aro.org>
Cc: Lorenzo Pieralisi <lpieralisi@...nel.org>,
	Krzysztof Wilczyński <kw@...ux.com>,
	Rob Herring <robh@...nel.org>, Bjorn Helgaas <bhelgaas@...gle.com>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Kishon Vijay Abraham I <kishon@...nel.org>,
	Bjorn Andersson <andersson@...nel.org>, linux-pci@...r.kernel.org,
	linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
	devicetree@...r.kernel.org
Subject: Re: [PATCH v2 05/13] PCI: endpoint: Assign PCI domain number for
 endpoint controllers

On Thu, Jul 18, 2024 at 02:11:00PM +0200, Konrad Dybcio wrote:
> On 17.07.2024 7:03 PM, Manivannan Sadhasivam via B4 Relay wrote:
> > From: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> > 
> > Right now, PCI endpoint subsystem doesn't assign PCI domain number for the
> > PCI endpoint controllers. But this domain number could be useful to the EPC
> > drivers to uniquely identify each controller based on the hardware instance
> > when there are multiple ones present in an SoC (even multiple RC/EP).
> > 
> > So let's make use of the existing pci_bus_find_domain_nr() API to allocate
> > domain numbers based on either Devicetree (linux,pci-domain) property or
> > dynamic domain number allocation scheme.
> > 
> > It should be noted that the domain number allocated by this API will be
> > based on both RC and EP controllers in a SoC. If the 'linux,pci-domain' DT
> > property is present, then the domain number represents the actual hardware
> > instance of the PCI endpoint controller. If not, then the domain number
> > will be allocated based on the PCI EP/RC controller probe order.
> > 
> > If the architecture doesn't support CONFIG_PCI_DOMAINS_GENERIC (rare), then
> > currently a warning is thrown to indicate that the architecture specific
> > implementation is needed.
> > 
> > Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> > ---
> >  drivers/pci/endpoint/pci-epc-core.c | 10 ++++++++++
> >  include/linux/pci-epc.h             |  2 ++
> >  2 files changed, 12 insertions(+)
> > 
> > diff --git a/drivers/pci/endpoint/pci-epc-core.c b/drivers/pci/endpoint/pci-epc-core.c
> > index 84309dfe0c68..7fa81b91e762 100644
> > --- a/drivers/pci/endpoint/pci-epc-core.c
> > +++ b/drivers/pci/endpoint/pci-epc-core.c
> > @@ -838,6 +838,9 @@ void pci_epc_destroy(struct pci_epc *epc)
> >  {
> >  	pci_ep_cfs_remove_epc_group(epc->group);
> >  	device_unregister(&epc->dev);
> > +
> > +	if (IS_ENABLED(CONFIG_PCI_DOMAINS_GENERIC))
> > +		pci_bus_release_domain_nr(NULL, &epc->dev);	
> 
> Shouldn't this be called before device_unregister? pci/remove.c
> does that (via pci_remove_bus() in pci_remove_root_bus())
> 

No, the release should follow the allocation order in __pci_epc_create. As per
that, pci_bus_release_domain_nr() should come last.

- Mani

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