[RFC qemu 4/6] hw/pcie: Provide a utility function for control of EP / SW USP link

[Jonathan Cameron <Jonathan.Cameron@huawei.com>]

Whilst similar to existing PCIESlot link configuration a few registers
need to be set differently so that the downstream device presents
a 'configured' state that is then used to 'train' the upstream port
on the link.  Basically that means setting the status register to
reflect it succeeding in training up to target settings.

Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
---
 include/hw/pci/pcie.h |  2 ++
 hw/pci/pcie.c         | 18 ++++++++++++++++++
 2 files changed, 20 insertions(+)

diff --git a/include/hw/pci/pcie.h b/include/hw/pci/pcie.h
index 5eddb90976..b8d59732bc 100644
--- a/include/hw/pci/pcie.h
+++ b/include/hw/pci/pcie.h
@@ -141,6 +141,8 @@ void pcie_acs_reset(PCIDevice *dev);
 void pcie_ari_init(PCIDevice *dev, uint16_t offset);
 void pcie_dev_ser_num_init(PCIDevice *dev, uint16_t offset, uint64_t ser_num);
 void pcie_ats_init(PCIDevice *dev, uint16_t offset, bool aligned);
+void pcie_cap_fill_link_ep_usp(PCIDevice *dev, PCIExpLinkWidth width,
+                               PCIExpLinkSpeed speed);
 
 void pcie_cap_slot_pre_plug_cb(HotplugHandler *hotplug_dev, DeviceState *dev,
                                Error **errp);
diff --git a/hw/pci/pcie.c b/hw/pci/pcie.c
index b14d59573e..89734b50a2 100644
--- a/hw/pci/pcie.c
+++ b/hw/pci/pcie.c
@@ -154,6 +154,24 @@ static void pcie_cap_fill_lnk(uint8_t *exp_cap, PCIExpLinkWidth width,
     }    
 }
 
+void pcie_cap_fill_link_ep_usp(PCIDevice *dev, PCIExpLinkWidth width,
+                               PCIExpLinkSpeed speed)
+{
+    uint8_t *exp_cap = dev->config + dev->exp.exp_cap;
+
+    /*
+     * For an end point or USP need to set the current status as well
+     * as the capabilities.
+     */
+    pci_long_test_and_clear_mask(exp_cap + PCI_EXP_LNKSTA,
+                                 PCI_EXP_LNKSTA_CLS | PCI_EXP_LNKSTA_NLW);
+    pci_long_test_and_set_mask(exp_cap + PCI_EXP_LNKSTA,
+                               QEMU_PCI_EXP_LNKSTA_NLW(width) |
+                               QEMU_PCI_EXP_LNKSTA_CLS(speed));
+    
+    pcie_cap_fill_lnk(exp_cap, width, speed);
+}
+
 static void pcie_cap_fill_slot_lnk(PCIDevice *dev)
 {
     PCIESlot *s = (PCIESlot *)object_dynamic_cast(OBJECT(dev), TYPE_PCIE_SLOT);
-- 
2.43.0