linux-kernel - Re: [PATCH v5 1/1] PCI: of: Remove max-link-speed generation validation

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Message-ID: <vpnjb4tip76yiy4uhn3frun6forrb57bq5czjvkx77uxt7ooc3@twemnyweabv6>
Date: Thu, 18 Dec 2025 18:36:01 +0530
From: Manivannan Sadhasivam <mani@...nel.org>
To: Hans Zhang <18255117159@....com>
Cc: bhelgaas@...gle.com, helgaas@...nel.org, ilpo.jarvinen@...ux.intel.com, 
	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 1/1] PCI: of: Remove max-link-speed generation
 validation

On Thu, Dec 18, 2025 at 08:59:09PM +0800, Hans Zhang wrote:
> The current implementation of of_pci_get_max_link_speed() validates
> max-link-speed property values to be in the range 1~4 (Gen1~Gen4).
> However, this creates maintenance overhead as each new PCIe generation
> requires updating this validation logic.
> 
> Since device tree binding validation already enforces the allowed
> values through the schema, and the callers of this function perform
> their own validation checks, this intermediate validation becomes
> redundant.
> 
> Furthermore, with upcoming SOCs using Synopsys/Cadence IP requiring
> Gen5/Gen6 support, removing this hardcoded check enables seamless
> support for future PCIe generations without requiring kernel updates
> for each new speed grade.
> 
> Remove the max-link-speed > 4 validation check while retaining the
> property existence and non-zero check. This simplifies maintenance
> and aligns with the existing validation architecture where DT binding
> and driver-level checks provide sufficient validation.
> 
> Signed-off-by: Hans Zhang <18255117159@....com>
> ---
> Changes for v5:
> - Delete the check for speed. (Mani)
> 
> Changes for v4:
> https://patchwork.kernel.org/project/linux-pci/patch/20251105134701.182795-1-18255117159@163.com/
> 
> - Add pcie_max_supported_link_speed.(Ilpo)
> 
> Changes for v3:
> https://patchwork.kernel.org/project/linux-pci/patch/20251101164132.14145-1-18255117159@163.com/
> 
> - Modify the commit message.
> - Add Reviewed-by tag.
> 
> Changes for v2:
> https://patchwork.kernel.org/project/linux-pci/cover/20250529021026.475861-1-18255117159@163.com/
> - The following files have been deleted:
>   Documentation/devicetree/bindings/pci/pci.txt
> 
>   Update to this file again:
>   dtschema/schemas/pci/pci-bus-common.yaml
> ---
>  drivers/pci/of.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/drivers/pci/of.c b/drivers/pci/of.c
> index 3579265f1198..1f8435780247 100644
> --- a/drivers/pci/of.c
> +++ b/drivers/pci/of.c
> @@ -889,8 +889,7 @@ int of_pci_get_max_link_speed(struct device_node *node)
>  {
>  	u32 max_link_speed;
>  
> -	if (of_property_read_u32(node, "max-link-speed", &max_link_speed) ||
> -	    max_link_speed == 0 || max_link_speed > 4)
> +	if (of_property_read_u32(node, "max-link-speed", &max_link_speed))
>  		return -EINVAL;

It'd be good to return the actual errno as of_property_read_u32() can return
-EINVAL, -ENODATA and -EOVERFLOW.

With that change,

Acked-by: Manivannan Sadhasivam <mani@...nel.org>

- Mani

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