On Sun, Jun 13, 2021 at 05:29:15PM +0800, Dongdong Liu wrote:
> PCIe spec 5.0r1.0 section 2.2.6.2 implementation note, In configurations
> where a Requester with 10-Bit Tag Requester capability needs to target
> multiple Completers, one needs to ensure that the Requester sends 10-Bit
> Tag Requests only to Completers that have 10-Bit Tag Completer capability.
> So we enable 10-Bit Tag Requester for root port only when the devices
> under the root port support 10-Bit Tag Completer.
>
> Signed-off-by: Dongdong Liu <liudongdong3@xxxxxxxxxx>
> ---
> drivers/pci/pcie/portdrv_pci.c | 75 ++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 75 insertions(+)
>
> diff --git a/drivers/pci/pcie/portdrv_pci.c b/drivers/pci/pcie/portdrv_pci.c
> index c7ff1ee..baf413f 100644
> --- a/drivers/pci/pcie/portdrv_pci.c
> +++ b/drivers/pci/pcie/portdrv_pci.c
> @@ -90,6 +90,78 @@ static const struct dev_pm_ops pcie_portdrv_pm_ops = {
> #define PCIE_PORTDRV_PM_OPS NULL
> #endif /* !PM */
>
> +static int pci_10bit_tag_comp_support(struct pci_dev *dev, void *data)
> +{
> + u8 *support = data;
> +
> + if (*support == 0)
> + return 0;
> +
> + if (!pci_is_pcie(dev)) {
> + *support = 0;
> + return 0;
> + }
> +
> + /*
> + * PCIe spec 5.0r1.0 section 2.2.6.2 implementation note.
> + * For configurations where a Requester with 10-Bit Tag Requester
> + * capability targets Completers where some do and some do not have
> + * 10-Bit Tag Completer capability, how the Requester determines which
> + * NPRs include 10-Bit Tags is outside the scope of this specification.
> + * So we do not consider hotplug scenario.
> + */
> + if (dev->is_hotplug_bridge) {
> + *support = 0;
> + return 0;
> + }
> +
> + if (!(dev->pcie_devcap2 & PCI_EXP_DEVCAP2_10BIT_TAG_COMP)) {
> + *support = 0;
> + return 0;
> + }
> +
> + return 0;
> +}
> +
> +static void pci_configure_rp_10bit_tag(struct pci_dev *dev)
> +{
> + u8 support = 1;
> + struct pci_dev *pchild;
> +
> + if (dev->subordinate == NULL)
> + return;
> +
> + /* If no devices under the root port, no need to enable 10-Bit Tag. */
> + pchild = list_first_entry_or_null(&dev->subordinate->devices,
> + struct pci_dev, bus_list);
> + if (pchild == NULL)
> + return;
pchild is never used after this check, so this could be simplified to
a list_empty(&dev->subordinate->devices).
