Re: [PATCH v6 3/3] PCI: dwc: Use common speed conversion function

[Ilpo Järvinen]

On Mon, 6 Apr 2026, Hans Zhang wrote:

> Replace the private switch-based speed conversion in
> dw_pcie_link_set_max_speed() with the public pci_bus_speed2lnkctl2()
> function.
> 
> This eliminates duplicate conversion logic and ensures consistency with
> other PCIe drivers, while handling invalid speeds by falling back to
> hardware capabilities.
> 
> Signed-off-by: Hans Zhang <18255117159@xxxxxxx>
> Acked-by: Manivannan Sadhasivam <mani@xxxxxxxxxx>
> ---
>  drivers/pci/controller/dwc/pcie-designware.c | 18 +++---------------
>  1 file changed, 3 insertions(+), 15 deletions(-)
> 
> diff --git a/drivers/pci/controller/dwc/pcie-designware.c b/drivers/pci/controller/dwc/pcie-designware.c
> index 06792ba92aa7..ab8dee5d6c7a 100644
> --- a/drivers/pci/controller/dwc/pcie-designware.c
> +++ b/drivers/pci/controller/dwc/pcie-designware.c
> @@ -861,24 +861,12 @@ static void dw_pcie_link_set_max_speed(struct dw_pcie *pci)
>  	ctrl2 = dw_pcie_readl_dbi(pci, offset + PCI_EXP_LNKCTL2);
>  	ctrl2 &= ~PCI_EXP_LNKCTL2_TLS;
>  
> -	switch (pcie_get_link_speed(pci->max_link_speed)) {
> -	case PCIE_SPEED_2_5GT:
> -		link_speed = PCI_EXP_LNKCTL2_TLS_2_5GT;
> -		break;
> -	case PCIE_SPEED_5_0GT:
> -		link_speed = PCI_EXP_LNKCTL2_TLS_5_0GT;
> -		break;
> -	case PCIE_SPEED_8_0GT:
> -		link_speed = PCI_EXP_LNKCTL2_TLS_8_0GT;
> -		break;
> -	case PCIE_SPEED_16_0GT:
> -		link_speed = PCI_EXP_LNKCTL2_TLS_16_0GT;
> -		break;
> -	default:
> +	link_speed = pcie_get_link_speed(pci->max_link_speed);
> +	link_speed = pci_bus_speed2lnkctl2(link_speed);

Its signature is:

u16 pci_bus_speed2lnkctl2(enum pci_bus_speed speed)

Using link_speed variable both for in and out does contradict with the
expected typing.

Maybe it would be beneficial to rename the current 'link_speed' to 
'ctrl2_speed' (or something along those lines) to differentiate Link 
Control 2 speed representation from PCI core's internal link speed 
representation. And then reintroduce link_speed variable as the 
pci_bus_speed. ...But this is just my suggestion, there may be better ways 
to untangle this type abuse.

> +	if (link_speed == 0) {
>  		/* Use hardware capability */
>  		link_speed = FIELD_GET(PCI_EXP_LNKCAP_SLS, cap);
>  		ctrl2 &= ~PCI_EXP_LNKCTL2_HASD;
> -		break;
>  	}
>  
>  	dw_pcie_writel_dbi(pci, offset + PCI_EXP_LNKCTL2, ctrl2 | link_speed);
> 

-- 
 i.