Re: [PATCH v3 1/3] PCI: Configure root port MPS during host probing

[Niklas Cassel <cassel@kernel.org>]

On Wed, May 07, 2025 at 01:34:37AM +0800, Hans Zhang wrote:

(snip)

>  static void pci_configure_mps(struct pci_dev *dev)
>  {
>  	struct pci_dev *bridge = pci_upstream_bridge(dev);
> @@ -2178,6 +2209,10 @@ static void pci_configure_mps(struct pci_dev *dev)
>  		return;
>  	}

We should probably add a comment explaining why we are doing this here.

Perhaps something like:

/*
 * Unless MPS strategy is PCIE_BUS_TUNE_OFF (don't touch MPS at all),
 * start off by setting root ports' MPS to MPSS. Depending on the MPS
 * strategy, and the MPSS of the devices below the root port, the MPS
 * of the root port might get overriden later.
 */


> +	if (pci_pcie_type(dev) == PCI_EXP_TYPE_ROOT_PORT &&
> +	    pcie_bus_config != PCIE_BUS_TUNE_OFF)
> +		pcie_write_mps(dev, 128 << dev->pcie_mpss);
> +
>  	if (!bridge || !pci_is_pcie(bridge))
>  		return;
>  


Kind regards,
Niklas