linux-kernel - Re: [PATCH 06/14] PCI: endpoint: Assign PCI domain number for endpoint controllers

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Message-ID: <20240716041416.GC3446@thinkpad>
Date: Tue, 16 Jul 2024 09:44:16 +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 06/14] PCI: endpoint: Assign PCI domain number for
 endpoint controllers

On Mon, Jul 15, 2024 at 10:02:18PM +0200, Konrad Dybcio wrote:
> On 15.07.2024 7:33 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.
> > 
> > Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> > ---
> 
> The PCI counterpart does some error checking and requires
> CONFIG_PCI_DOMAINS_GENERIC. Is that something that needs to be taken
> care of here as well?
> 

Good catch. I excluded the Kconfig check initially during development as it was
selected by most of the architectures. But I clearly failed to revisit it later.

And yes, we do need to use the guard. I also missed freeing the domain during
epc_destroy() which I'll fix in next revision. Thanks!

- Mani

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