linux-kernel - Re: [RFC,v14 4/5] arm64: tegra: Add PCIe port node with PCIe WAKE# for C1 controller

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Message-ID: <20231207093112.GH2932@thinkpad>
Date:   Thu, 7 Dec 2023 15:01:12 +0530
From:   Manivannan Sadhasivam <mani@...nel.org>
To:     Manikanta Maddireddy <mmaddireddy@...dia.com>
Cc:     bhelgaas@...gle.com, thierry.reding@...il.com, petlozup@...dia.com,
        rafael.j.wysocki@...el.com, lpieralisi@...nel.org, robh@...nel.org,
        jeffy.chen@...k-chips.com, krzysztof.kozlowski+dt@...aro.org,
        jonathanh@...dia.com, dmitry.osipenko@...labora.com,
        viresh.kumar@...aro.org, gregkh@...uxfoundation.org,
        steven.price@....com, kw@...ux.com, linux-pci@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-tegra@...r.kernel.org, linux-pm@...r.kernel.org,
        vidyas@...dia.com
Subject: Re: [RFC,v14 4/5] arm64: tegra: Add PCIe port node with PCIe WAKE#
 for C1 controller

On Thu, Dec 07, 2023 at 02:23:46PM +0530, Manikanta Maddireddy wrote:
> 
> On 07-12-2023 13:29, Manivannan Sadhasivam wrote:
> > External email: Use caution opening links or attachments
> > 
> > 
> > On Thu, Dec 07, 2023 at 12:54:04PM +0530, Manikanta Maddireddy wrote:
> > > On 06-12-2023 21:06, Manivannan Sadhasivam wrote:
> > > > External email: Use caution opening links or attachments
> > > > 
> > > > 
> > > > On Wed, Feb 08, 2023 at 04:46:44PM +0530, Manikanta Maddireddy wrote:
> > > > > Add PCIe port node under the PCIe controller-1 device tree node to support
> > > > > PCIe WAKE# interrupt for WiFi.
> > > > > 
> > > > > Signed-off-by: Manikanta Maddireddy <mmaddireddy@...dia.com>
> > > > > ---
> > > > > 
> > > > > Changes in v14:
> > > > > New patch in the series to support PCIe WAKE# in NVIDIA Jetson AGX Orin.
> > > > > 
> > > > >    .../dts/nvidia/tegra234-p3737-0000+p3701-0000.dts     | 11 +++++++++++
> > > > >    1 file changed, 11 insertions(+)
> > > > > 
> > > > > diff --git a/arch/arm64/boot/dts/nvidia/tegra234-p3737-0000+p3701-0000.dts b/arch/arm64/boot/dts/nvidia/tegra234-p3737-0000+p3701-0000.dts
> > > > > index 8a9747855d6b..9c89be263141 100644
> > > > > --- a/arch/arm64/boot/dts/nvidia/tegra234-p3737-0000+p3701-0000.dts
> > > > > +++ b/arch/arm64/boot/dts/nvidia/tegra234-p3737-0000+p3701-0000.dts
> > > > > @@ -2147,6 +2147,17 @@ pcie@...00000 {
> > > > > 
> > > > >                         phys = <&p2u_hsio_3>;
> > > > >                         phy-names = "p2u-0";
> > > > > +
> > > > > +                     pci@0,0 {
> > > > > +                             reg = <0x0000 0 0 0 0>;
> > > > > +                             #address-cells = <3>;
> > > > > +                             #size-cells = <2>;
> > > > > +                             ranges;
> > > > > +
> > > > > +                             interrupt-parent = <&gpio>;
> > > > > +                             interrupts = <TEGRA234_MAIN_GPIO(L, 2) IRQ_TYPE_LEVEL_LOW>;
> > > > > +                             interrupt-names = "wakeup";
> > > > WAKE# should be part of the PCIe controller, not device. And the interrupt name
> > > > should be "wake".
> > > > 
> > > > - Mani
> > > Hi,
> > > 
> > > Please refer to the discussion in below link, WAKE# is per PCI bridge.
> > > https://patchwork.ozlabs.org/project/linux-pci/patch/20171226020806.32710-2-jeffy.chen@rock-chips.com/
> > > 
> > PCIe Host controller (RC) usually represents host bridge + PCI-PCI bridge. We do
> > not represent the PCI-PCI bridge in devicetree for any platforms, but only RC as
> > a whole.
> > 
> > Moreover, PERST# is already defined in RC node. So it becomes confusing if
> > WAKE# is defined in a child node representing bridge.
> > 
> > So please move WAKE# to RC node.
> > 
> > - Mani
> 
> Hi,
> 
> We can define PCI-PCI bridge in device tree, refer to below device tree
> which has 3 ports under a controller,
> with PERST#(reset-gpios) defined per port.
> 
> https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/tree/arch/arm64/boot/dts/apple/t8103.dtsi#n749
> 

Hmm. For RCs with single bridge, we never defined a DT node (atleast on Qcom
platforms). But I think it is the time to fix them.

> Also, of_pci_setup_wake_irq() in below patch is parsing "wakeup" from PCI
> bridge, not from the host bridge.
> https://patchwork.ozlabs.org/project/linux-pci/patch/20230208111645.3863534-4-mmaddireddy@nvidia.com/
> 

I didn't say that WAKE# should be parsed from host bridge, it doesn't make
sense. But I get your point.

> If a controller has only one port it has to define a PCI bridge under
> controller device tree node and
> add wakeup interrupt property, refer to below patch from original author.
> 
> https://www.spinics.net/lists/linux-pci/msg135569.html
> 

Yes, I agree. Thanks for the clarification.

- Mani

> Thanks,
> Manikanta
> > 
> > > I carried wakeup name defined in previous version, but wake seems to be
> > > sufficient.
> > > 
> > > Thanks,
> > > Manikanta
> > > > > +                     };
> > > > >                 };
> > > > > 
> > > > >                 pcie@...60000 {
> > > > > --
> > > > > 2.25.1
> > > > > 
> > > > --
> > > > மணிவண்ணன் சதாசிவம்
> > --
> > மணிவண்ணன் சதாசிவம்

-- 
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