Re: [PATCH 2/3] PCI: of: create DT nodes for PCI devices if they do not exists

From: Lizhi Hou <lizhi.hou@xilinx.com>
To: "Clément Léger" <clement.leger@bootlin.com>,
	"Bjorn Helgaas" <helgaas@kernel.org>
Cc: Rob Herring <robh+dt@kernel.org>,
	Frank Rowand <frowand.list@gmail.com>,
	Pantelis Antoniou <pantelis.antoniou@konsulko.com>,
	Bjorn Helgaas <bhelgaas@google.com>,
	Allan Nielsen <allan.nielsen@microchip.com>,
	Horatiu Vultur <horatiu.vultur@microchip.com>,
	Steen Hegelund <steen.hegelund@microchip.com>,
	Thomas Petazzoni <thomas.petazonni@bootlin.com>,
	Alexandre Belloni <alexandre.belloni@bootlin.com>,
	Mark Brown <broonie@kernel.org>,
	Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
	Jakub Kicinski <kuba@kernel.org>,
	Hans de Goede <hdegoede@redhat.com>, Andrew Lunn <andrew@lunn.ch>,
	<devicetree@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
	<linux-pci@vger.kernel.org>, Rob Herring <robh@kernel.org>
Subject: Re: [PATCH 2/3] PCI: of: create DT nodes for PCI devices if they do not exists
Date: Wed, 18 May 2022 12:22:07 -0700	[thread overview]
Message-ID: <c2f6d576-b48b-d1a7-2e4d-bbedea969f52@xilinx.com> (raw)
In-Reply-To: <20220504154303.5cdf8cc2@fixe.home>

On 5/4/22 06:43, Clément Léger wrote:
> Le Tue, 3 May 2022 17:53:53 -0500,
> Bjorn Helgaas <helgaas@kernel.org> a écrit :
>
>> In subject:
>>
>>    PCI: of: Create DT nodes ... if they do not exist
>>
>> The subject could be read as saying that you're going to create DT
>> nodes before the PCI devices exist, but I think you mean that when we
>> enumerate a PCI devices, we're *always* going to create a DT node for
>> it, even if the DT didn't mention it.
> Hi Bjorn,
>
> Indeed ! I'll modify that.

Linking the dynamic generated dt node to PCIe device through 
pci_dev->dev.of_node may cause issues. Kernel and driver code may check 
of_node pointer and run complete different code path if of_node is not 
NULL.

For example:  in of_irq_parse_pci(): 
https://elixir.bootlin.com/linux/v5.18-rc2/source/drivers/pci/of.c#L492

I encountered different issues when I tried to create a prototype. And I 
have sent all may questions/thoughts through 
https://lore.kernel.org/lkml/79e4c876-e5a4-861f-cfbc-c75ed1a07ddd@xilinx.com/#t

I am wondering what would be the right way to resolve it?

Thanks,

Lizhi

>
>> Maybe something like:
>>
>>    PCI: of: Create DT node for every PCI device
>>
>> although I see Rob thinks this should be done on demand instead of
>> doing it for every device, which sounds sensible to me.
> Agreed, I'll rework this series.
>
> Thanks,
>
>> On Wed, Apr 27, 2022 at 11:45:01AM +0200, Clément Léger wrote:
>>> In order to apply overlays to PCI device nodes, the nodes must first
>>> exist. This commit add support to populate a skeleton tree for PCI bus
>>> and devices. These nodes can then be used by drivers to apply overlays.
>> s/This commit add support/Add support/
>>
>> Bjorn
>
>