Re: [PATCH RFC V3 2/2] PCI: Create device tree node for selected devices

[Lizhi Hou]

Hi Bjorn,

Thanks for your comments. I will fix all these with next submission.

Lizhi

On 11/7/22 13:05, Bjorn Helgaas wrote:
> On Fri, Nov 04, 2022 at 08:24:14AM -0700, Lizhi Hou wrote:
> > The PCIe endpoint device such as Xilinx Alveo PCIe card maps the register
> > spaces from multiple hardware peripherals to its PCIe BAR. Normally,
> > the PCI core discovers devices and BARs using the PCI enumeration process.
> > There is no infrastructure to discover the hardware peripherals that are
> > present in a PCI device, and which can be accessed through the PCI BARs.
> >
> > For Alveo PCIe card, the card firmware provides a flattened device tree to
> > describe the hardware peripherals on its BARs. The Alveo card driver can
> > load this flattened device tree and leverage device tree framework to
> > generate platform devices for the hardware peripherals eventually.
> >
> > Apparently, the device tree framework requires a device tree node for the
> > PCIe device. Thus, it can generate the device tree nodes for hardware
> > peripherals underneath. Because PCIe is self discoverable bus, there might
> > not be a device tree node created for PCIe devices. This patch is to add
> > support to generate device tree node for PCIe devices. It introduces a
> > kernel option. When the option is turned on, the kernel will generate
> Specify the kernel option here.  These last two sentences should
> probably be a separate paragraph because they say specifically what
> this patch does.
>
> > device tree nodes for PCI bridges unconditionally.
> > It will also generate
> > a device tree node for Xilinx Alveo U50 by using PCI quirks.
> I think I would split the Xilinx Alveo U50 quirk to a separate patch
> from the infrastructure and make this patch more generic.
>
> > +config PCI_DYNAMIC_OF_NODES
> > +	bool "Device tree node for PCI devices"
> > +	depends on OF
> > +	select OF_DYNAMIC
> > +	help
> > +	  This option enables support for generating device tree nodes for some
> > +	  PCI devices. Thus, the driver of this kind can load and overlay
> > +	  flattened device tree for its downstream devices.
> > +
> > +	  Once this option is selected, the device tree nodes will be generated
> > +	  for all PCI/PCIE bridges.
> PCI/PCIe
>
> Actually, in this context (and in the commit log), you should just say
> "PCI" because there's nothing PCIe-specific here.
>
> > +void of_pci_make_dev_node(struct pci_dev *pdev)
> > +{
> > +	struct device_node *parent, *dt_node = NULL;
> > +	const char *pci_type = "dev";
> > +	struct of_changeset *cset;
> > +	const char *full_name;
> > +	int ret;
> > +
> > +	/*
> > +	 * if there is already a device tree node linked to this device,
> > +	 * return immediately.
> s/if there/If there/
>
> > +	 */
> > +	if (pci_device_to_OF_node(pdev))
> > +		return;
> > +
> > +	/* check if there is device tree node for parent device */
> s/check/Check/
>
> Follow the style of the file, which is "capitalize English sentences."