xen/arm: Implement pci access functions

Implement generic pci access functions to read/write the configuration
space.

Signed-off-by: Rahul Singh <rahul.singh@arm.com>
Reviewed-by: Bertrand Marquis <bertrand.marquis@arm.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>

xen/arch/arm/pci/pci-access.c

@@ -16,6 +16,7 @@
 #include <asm/io.h>
 
 #define INVALID_VALUE (~0U)
+#define PCI_ERR_VALUE(len) GENMASK(0, len * 8)
 
 int pci_generic_config_read(struct pci_host_bridge *bridge, pci_sbdf_t sbdf,
                             uint32_t reg, uint32_t len, uint32_t *value)
@@ -72,6 +73,62 @@ int pci_generic_config_write(struct pci_host_bridge *bridge, pci_sbdf_t sbdf,
     return 0;
 }
 
+static uint32_t pci_config_read(pci_sbdf_t sbdf, unsigned int reg,
+                                unsigned int len)
+{
+    uint32_t val = PCI_ERR_VALUE(len);
+    struct pci_host_bridge *bridge = pci_find_host_bridge(sbdf.seg, sbdf.bus);
+
+    if ( unlikely(!bridge) )
+        return val;
+
+    if ( unlikely(!bridge->ops->read) )
+        return val;
+
+    bridge->ops->read(bridge, sbdf, reg, len, &val);
+
+    return val;
+}
+
+static void pci_config_write(pci_sbdf_t sbdf, unsigned int reg,
+                             unsigned int len, uint32_t val)
+{
+    struct pci_host_bridge *bridge = pci_find_host_bridge(sbdf.seg, sbdf.bus);
+
+    if ( unlikely(!bridge) )
+        return;
+
+    if ( unlikely(!bridge->ops->write) )
+        return;
+
+    bridge->ops->write(bridge, sbdf, reg, len, val);
+}
+
+/*
+ * Wrappers for all PCI configuration access functions.
+ */
+
+#define PCI_OP_WRITE(size, type)                            \
+    void pci_conf_write##size(pci_sbdf_t sbdf,              \
+                              unsigned int reg, type val)   \
+{                                                           \
+    pci_config_write(sbdf, reg, size / 8, val);             \
+}
+
+#define PCI_OP_READ(size, type)                             \
+    type pci_conf_read##size(pci_sbdf_t sbdf,               \
+                              unsigned int reg)             \
+{                                                           \
+    return pci_config_read(sbdf, reg, size / 8);            \
+}
+
+PCI_OP_READ(8, uint8_t)
+PCI_OP_READ(16, uint16_t)
+PCI_OP_READ(32, uint32_t)
+PCI_OP_WRITE(8, uint8_t)
+PCI_OP_WRITE(16, uint16_t)
+PCI_OP_WRITE(32, uint32_t)
+
 /*
  * Local variables:
  * mode: C

xen/arch/arm/pci/pci-host-common.c

@@ -236,6 +236,25 @@ err_exit:
     return err;
 }
 
+/*
+ * This function will lookup an hostbridge based on the segment and bus
+ * number.
+ */
+struct pci_host_bridge *pci_find_host_bridge(uint16_t segment, uint8_t bus)
+{
+    struct pci_host_bridge *bridge;
+
+    list_for_each_entry( bridge, &pci_host_bridges, node )
+    {
+        if ( bridge->segment != segment )
+            continue;
+        if ( (bus < bridge->cfg->busn_start) || (bus > bridge->cfg->busn_end) )
+            continue;
+        return bridge;
+    }
+
+    return NULL;
+}
 /*
  * Local variables:
  * mode: C

xen/include/asm-arm/pci.h

@@ -81,6 +81,7 @@ int pci_generic_config_write(struct pci_host_bridge *bridge, pci_sbdf_t sbdf,
                              uint32_t reg, uint32_t len, uint32_t value);
 void __iomem *pci_ecam_map_bus(struct pci_host_bridge *bridge,
                                pci_sbdf_t sbdf, uint32_t where);
+struct pci_host_bridge *pci_find_host_bridge(uint16_t segment, uint8_t bus);
 
 static always_inline bool is_pci_passthrough_enabled(void)
 {