Re: [PATCH v2] PCI: Add D3 support for PCI bridges in DT based platforms

[Lukas Wunner <lukas@wunner.de>]

On Wed, Feb 14, 2024 at 02:18:31PM +0530, Manivannan Sadhasivam wrote:
> +/**
> + * of_pci_bridge_d3 - Check if the bridge is supporting D3 states or not
> + *
> + * @node: device tree node of the bridge
> + *
> + * Return: True if the bridge is supporting D3 states, False otherwise.

A lot of kernel-doc uses %true and %false.


> +bool of_pci_bridge_d3(struct device_node *node)
> +{
> +	return of_property_read_bool(node, "supports-d3");
> +}

What's the difference between of_property_read_bool() and
of_property_present()?  When should one use which?
The former has 691 occurrences in the tree, the latter 120.
The latter would seem more "literary" / readable here,
but maybe that's just me.


> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -1142,6 +1142,9 @@ static inline bool platform_pci_bridge_d3(struct pci_dev *dev)
>  	if (pci_use_mid_pm())
>  		return false;
>  
> +	if (dev->dev.of_node)
> +		return of_pci_bridge_d3(dev->dev.of_node);
> +
>  	return acpi_pci_bridge_d3(dev);
>  }

This will result in an unnecessary test on non-DT platforms (e.g. ACPI)
whether dev->dev.of_node is set.

Please use dev_of_node() instead of "dev->dev.of_node" so that the
code added here can be optimized away by the compiler on non-DT
platforms (due to the IS_ENABLED(CONFIG_OF)).

Thanks,

Lukas