PCI: vmd: Add offset to bus numbers if necessary

Depending on platform configuration, certain VMD devices may have an
additional configuration option which specifies the range of bus numbers
allowed in a VMD PCIe domain. We determine this requirement by checking
the value of two vendor specific config registers in the VMD endpoint:

 VMCAP[0] | VMCONFIG[9:8] | Bus Numbers
----------------------------------------
    0     |       *       |     0-255
    1     |      00       |     0-127
    1     |      01       |   128-255
    1     |      10       |     0-255

This feature is also added as a bit in driver_data, to allow future
conforming device ids which support these features to be enabled through
sysfs new_id.

Signed-off-by: Jon Derrick <jonathan.derrick@intel.com>
[lorenzo.pieralisi@arm.com: updated commit subject]
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>

1 files changed, 29 insertions, 5 deletions

diff --git a/drivers/pci/host/vmd.c b/drivers/pci/host/vmd.c
index 1544121b74f3..34fa6cf0b0ee 100644
--- a/drivers/pci/host/vmd.c
+++ b/drivers/pci/host/vmd.c
@@ -24,6 +24,10 @@
 #define VMD_MEMBAR1     2
 #define VMD_MEMBAR2     4
 
+#define PCI_REG_VMCAP           0x40
+#define BUS_RESTRICT_CAP(vmcap) (vmcap & 0x1)
+#define PCI_REG_VMCONFIG        0x44
+#define BUS_RESTRICT_CFG(vmcfg) ((vmcfg >> 8) & 0x3)
 #define PCI_REG_VMLOCK          0x70
 #define MB2_SHADOW_EN(vmlock)   (vmlock & 0x2)
 
@@ -34,6 +38,12 @@ enum vmd_features {
          * resource assignment to enable guest virtualization
          */
         VMD_FEAT_HAS_MEMBAR_SHADOW      = (1 << 0),
+
+        /*
+         * Device may provide root port configuration information which limits
+         * bus numbering
+         */
+        VMD_FEAT_HAS_BUS_RESTRICTIONS   = (1 << 1),
 };
 
 /*
@@ -567,7 +577,7 @@ static int vmd_enable_domain(struct vmd_dev *vmd, unsigned long features)
         unsigned long flags;
         LIST_HEAD(resources);
         resource_size_t offset[2] = {0};
-        resource_size_t membar2_offset = 0x2000;
+        resource_size_t membar2_offset = 0x2000, busn_start = 0;
 
         /*
          * Shadow registers may exist in certain VMD device ids which allow
@@ -598,11 +608,25 @@ static int vmd_enable_domain(struct vmd_dev *vmd, unsigned long features)
                 }
         }
 
+        /*
+         * Certain VMD devices may have a root port configuration option which
+         * limits the bus range to between 0-127 or 128-255
+         */
+        if (features & VMD_FEAT_HAS_BUS_RESTRICTIONS) {
+                u32 vmcap, vmconfig;
+
+                pci_read_config_dword(vmd->dev, PCI_REG_VMCAP, &vmcap);
+                pci_read_config_dword(vmd->dev, PCI_REG_VMCONFIG, &vmconfig);
+                if (BUS_RESTRICT_CAP(vmcap) &&
+                    (BUS_RESTRICT_CFG(vmconfig) == 0x1))
+                        busn_start = 128;
+        }
+
         res = &vmd->dev->resource[VMD_CFGBAR];
         vmd->resources[0] = (struct resource) {
                 .name  = "VMD CFGBAR",
-                .start = 0,
-                .end   = (resource_size(res) >> 20) - 1,
+                .start = busn_start,
+                .end   = busn_start + (resource_size(res) >> 20) - 1,
                 .flags = IORESOURCE_BUS | IORESOURCE_PCI_FIXED,
         };
 
@@ -670,8 +694,8 @@ static int vmd_enable_domain(struct vmd_dev *vmd, unsigned long features)
         pci_add_resource_offset(&resources, &vmd->resources[1], offset[0]);
         pci_add_resource_offset(&resources, &vmd->resources[2], offset[1]);
 
-        vmd->bus = pci_create_root_bus(&vmd->dev->dev, 0, &vmd_ops, sd,
-                                       &resources);
+        vmd->bus = pci_create_root_bus(&vmd->dev->dev, busn_start, &vmd_ops,
+                                       sd, &resources);
         if (!vmd->bus) {
                 pci_free_resource_list(&resources);
                 irq_domain_remove(vmd->irq_domain);