linux-kernel - Re: [RFC 3/9] PCI/portdrv: create platform devices for child OF nodes

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Message-ID: <20240111150201.GA28409@wunner.de>
Date: Thu, 11 Jan 2024 16:02:01 +0100
From: Lukas Wunner <lukas@...ner.de>
To: Bartosz Golaszewski <brgl@...ev.pl>
Cc: Kalle Valo <kvalo@...nel.org>, "David S . Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Rob Herring <robh+dt@...nel.org>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Bjorn Andersson <andersson@...nel.org>,
	Konrad Dybcio <konrad.dybcio@...aro.org>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will@...nel.org>, Bjorn Helgaas <bhelgaas@...gle.com>,
	Heiko Stuebner <heiko@...ech.de>,
	Jernej Skrabec <jernej.skrabec@...il.com>,
	Chris Morgan <macromorgan@...mail.com>,
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	Terry Bowman <terry.bowman@....com>,
	Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>,
	Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
	Huacai Chen <chenhuacai@...nel.org>, Alex Elder <elder@...aro.org>,
	Srini Kandagatla <srinivas.kandagatla@...aro.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-arm-msm@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-pci@...r.kernel.org,
	Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
Subject: Re: [RFC 3/9] PCI/portdrv: create platform devices for child OF nodes

On Thu, Jan 11, 2024 at 05:09:09AM -0600, Bartosz Golaszewski wrote:
> On Thu, 11 Jan 2024 11:42:11 +0100, Lukas Wunner <lukas@...ner.de> said:
> > On Wed, Jan 10, 2024 at 02:18:30PM -0600, Bartosz Golaszewski wrote:
> >> On Wed, 10 Jan 2024 17:41:05 +0100, Lukas Wunner <lukas@...ner.de> said:
> >> > On Wed, Jan 10, 2024 at 05:26:52PM +0100, Bartosz Golaszewski wrote:
> >> > > Seems like the following must be true but isn't in my case (from
> >> > > pci_bus_add_device()):
> >> > >
> >> > >     if (pci_is_bridge(dev))
> >> > >         of_pci_make_dev_node(dev);
> >> > >
> >> > > Shouldn't it evaluate to true for ports?
> >> >
> >> > It should.
> >> >
> >> > What does "lspci -vvvvxxxx -s BB:DD.F" say for the port in question?
> 
> # lspci -vvvvxxxx -s 0000:00:00
> 0000:00:00.0 PCI bridge: Qualcomm Technologies, Inc Device 010b
> (prog-if 00 [Normal decode])
> 	Device tree node: /sys/firmware/devicetree/base/soc@...cie@...0000/pcie@0
[...]
> 00: cb 17 0b 01 07 05 10 00 00 00 04 06 00 00 01 00
                                                ^^
The Header Type in config space is 0x1, i.e. PCI_HEADER_TYPE_BRIDGE.

So pci_is_bridge(dev) does return true (unlike what you write above)
and control flow enters of_pci_make_dev_node().

But perhaps of_pci_make_dev_node() returns immediately because:

	/*
	 * If there is already a device tree node linked to this device,
	 * return immediately.
	 */
	if (pci_device_to_OF_node(pdev))
		return;

..and lspci does list a devicetree node for that Root Port.

In any case, of_pci_make_dev_node() is the right place to add
the call to of_platform_populate().  Just make sure it's called
even if there is already a DT node for the Root Port itself.

Thanks,

Lukas