linux-kernel - Re: [PATCH v4 09/10] dt-bindings: PCI: qcom,pcie-sc7280: Add 'global' interrupt

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Message-ID: <20250305074838.yjhvpqrm4xrzta2y@thinkpad>
Date: Wed, 5 Mar 2025 13:18:38 +0530
From: Manivannan Sadhasivam <mani@...nel.org>
To: Jorge Ramirez <jorge.ramirez@....qualcomm.com>
Cc: Bjorn Andersson <andersson@...nel.org>,
	Krzysztof Kozlowski <krzk@...nel.org>,
	Krishna Chaitanya Chundru <krishna.chundru@....qualcomm.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Lorenzo Pieralisi <lpieralisi@...nel.org>,
	Krzysztof Wilczyński <kw@...ux.com>,
	Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	chaitanya chundru <quic_krichai@...cinc.com>,
	Konrad Dybcio <konradybcio@...nel.org>,
	cros-qcom-dts-watchers@...omium.org,
	Jingoo Han <jingoohan1@...il.com>,
	Bartosz Golaszewski <brgl@...ev.pl>, quic_vbadigan@...cnic.com,
	amitk@...nel.org, dmitry.baryshkov@...aro.org,
	linux-pci@...r.kernel.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH v4 09/10] dt-bindings: PCI: qcom,pcie-sc7280: Add
 'global' interrupt

On Wed, Mar 05, 2025 at 08:36:26AM +0100, Jorge Ramirez wrote:
> On 26/02/25 10:29:43, Bjorn Andersson wrote:
> > On Wed, Feb 26, 2025 at 08:32:42AM +0100, Krzysztof Kozlowski wrote:
> > > On Tue, Feb 25, 2025 at 03:04:06PM +0530, Krishna Chaitanya Chundru wrote:
> > > > Qcom PCIe RC controllers are capable of generating 'global' SPI interrupt
> > > > to the host CPU. This interrupt can be used by the device driver to handle
> > > > PCIe link specific events such as Link up and Link down, which give the
> > > > driver a chance to start bus enumeration on its own when link is up and
> > > > initiate link training if link goes to a bad state. The PCIe driver can
> > > > still work without this interrupt but it will provide a nice user
> > > > experience when device gets plugged and removed.
> > > > 
> > > > Hence, document it in the binding along with the existing MSI interrupts.
> > > > Global interrupt is parsed as optional in driver, so adding it in bindings
> > > > will not break the ABI.
> > > > 
> > > > Signed-off-by: Krishna Chaitanya Chundru <krishna.chundru@....qualcomm.com>
> > > > ---
> > > >  Documentation/devicetree/bindings/pci/qcom,pcie-sc7280.yaml | 8 +++++---
> > > >  1 file changed, 5 insertions(+), 3 deletions(-)
> > > > 
> > > > diff --git a/Documentation/devicetree/bindings/pci/qcom,pcie-sc7280.yaml b/Documentation/devicetree/bindings/pci/qcom,pcie-sc7280.yaml
> > > > index 76cb9fbfd476..7ae09ba8da60 100644
> > > > --- a/Documentation/devicetree/bindings/pci/qcom,pcie-sc7280.yaml
> > > > +++ b/Documentation/devicetree/bindings/pci/qcom,pcie-sc7280.yaml
> > > > @@ -54,7 +54,7 @@ properties:
> > > >  
> > > >    interrupts:
> > > >      minItems: 8
> > > > -    maxItems: 8
> > > > +    maxItems: 9
> > > >  
> > > >    interrupt-names:
> > > >      items:
> > > > @@ -66,6 +66,7 @@ properties:
> > > >        - const: msi5
> > > >        - const: msi6
> > > >        - const: msi7
> > > > +      - const: global
> > > 
> > > Either context is missing or these are not synced with interrupts.
> > > 
> > 
> > I think the patch context ("properties") is confusing here, but it looks
> > to me that these are in sync: interrupts is defined to have 8 items, and
> > interrupt-names is a list of msi0 through msi7.
> > 
> > @Krishna, these two last patches (adding the global interrupt) doesn't
> > seem strongly connected to the switch patches. So, if Krzysztof agrees
> > with above assessment, please submit them separately (i.e. a new series,
> > 2 patches, v5).
> 
> um, but without these two patches, the functionality is broken requiring
> users to manually rescan the pci bus (ie, via sysfs) to see what is
> behind the bridge.
> 

It is not *broken* actually. The series is for enabling the PCIe switch and the
'global' IRQ is a host behavior. So technically both are not dependent on each
other.

> shouldnt the set include all the necessary patches? 
> 

FWIW, I have submitted a series that adds the IRQ for most of the arm64
platforms:
https://lore.kernel.org/linux-arm-msm/20250227-pcie-global-irq-v1-0-2b70a7819d1e@linaro.org/

There is a possibility that the above series could get merged before this one.

- Mani

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