Re: [PATCH] PCI: Align MPS to upstream bridge for SAFE and PERFORMANCE mode

[Tyler Hicks <tyhicks@linux.microsoft.com>]

On 2022-06-10 23:01:31, Zhiqiang Hou wrote:
> From: Hou Zhiqiang <Zhiqiang.Hou@nxp.com>
> 
> The commit 27d868b5e6cf ("PCI: Set MPS to match upstream bridge")
> made the device's MPS matches upstream bridge for PCIE_BUS_DEFAULT
> mode, so that it's more likely that a hot-added device will work in
> a system with an optimized MPS configuration.
> 
> Obviously, the Linux itself optimizes the MPS settings in the
> PCIE_BUS_SAFE and PCIE_BUS_PERFORMANCE mode, so let's do this also
> for these modes.
> 
> Signed-off-by: Hou Zhiqiang <Zhiqiang.Hou@nxp.com>
> ---

Hi Bjorn - We have some interest in this patch and I am hoping it can be
considered in preparation for v6.1. I took a look at it and it makes
sense to me but I'm not an expert in this area. Thanks!

Tyler

>  drivers/pci/probe.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
> index 17a969942d37..2c5a1aefd9cb 100644
> --- a/drivers/pci/probe.c
> +++ b/drivers/pci/probe.c
> @@ -2034,7 +2034,9 @@ static void pci_configure_mps(struct pci_dev *dev)
>  	 * Fancier MPS configuration is done later by
>  	 * pcie_bus_configure_settings()
>  	 */
> -	if (pcie_bus_config != PCIE_BUS_DEFAULT)
> +	if (pcie_bus_config != PCIE_BUS_DEFAULT &&
> +	    pcie_bus_config != PCIE_BUS_SAFE &&
> +	    pcie_bus_config != PCIE_BUS_PERFORMANCE)
>  		return;
>  
>  	mpss = 128 << dev->pcie_mpss;
> @@ -2047,7 +2049,7 @@ static void pci_configure_mps(struct pci_dev *dev)
>  
>  	rc = pcie_set_mps(dev, p_mps);
>  	if (rc) {
> -		pci_warn(dev, "can't set Max Payload Size to %d; if necessary, use \"pci=pcie_bus_safe\" and report a bug\n",
> +		pci_warn(dev, "can't set Max Payload Size to %d; if necessary, use \"pci=pcie_bus_peer2peer\" and report a bug\n",
>  			 p_mps);
>  		return;
>  	}
> -- 
> 2.17.1
>