From 60db3a4d8cc9073cf56264785197ba75ee1caca4 Mon Sep 17 00:00:00 2001 From: Sinan Kaya Date: Fri, 20 Jan 2017 09:16:51 -0500 Subject: [PATCH] PCI: Enable PCIe Extended Tags if supported Every PCIe device can generate 5-bit transaction Tags, which allow up to 32 concurrent requests. Some devices can generate 8-bit Extended Tags, which allow up to 256 concurrent requests. Per the ECN mentioned below, all PCIe Receivers are expected to support Extended Tags, so devices are allowed (but not required) to enable them by default. If a device supports Extended Tags but does not enable them by default, enable them. This allows the device to have up to 256 outstanding transactions at a time, which may improve performance. [bhelgaas: changelog, check for PCIe device] Link: https://pcisig.com/sites/default/files/specification_documents/ECN_Extended_Tag_Enable_Default_05Sept2008_final.pdf Signed-off-by: Sinan Kaya Signed-off-by: Bjorn Helgaas --- drivers/pci/probe.c | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c index aca5b2466adb..3abc94212197 100644 --- a/drivers/pci/probe.c +++ b/drivers/pci/probe.c @@ -1661,12 +1661,30 @@ static void program_hpp_type2(struct pci_dev *dev, struct hpp_type2 *hpp) */ } +static void pci_configure_extended_tags(struct pci_dev *dev) +{ + u32 dev_cap; + int ret; + + if (!pci_is_pcie(dev)) + return; + + ret = pcie_capability_read_dword(dev, PCI_EXP_DEVCAP, &dev_cap); + if (ret) + return; + + if (dev_cap & PCI_EXP_DEVCAP_EXT_TAG) + pcie_capability_set_word(dev, PCI_EXP_DEVCTL, + PCI_EXP_DEVCTL_EXT_TAG); +} + static void pci_configure_device(struct pci_dev *dev) { struct hotplug_params hpp; int ret; pci_configure_mps(dev); + pci_configure_extended_tags(dev); memset(&hpp, 0, sizeof(hpp)); ret = pci_get_hp_params(dev, &hpp); -- 2.20.1