dm: pci: Add APIs to find capability and extended capability

This introduces two new APIs dm_pci_find_capability() and
dm_pci_find_ext_capability() to get PCI capability address and
PCI express extended capability address for a given PCI device.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

drivers/pci/pci-uclass.c

@@ -1320,6 +1320,74 @@ void *dm_pci_map_bar(struct udevice *dev, int bar, int flags)
 	return dm_pci_bus_to_virt(dev, pci_bus_addr, flags, 0, MAP_NOCACHE);
 }
 
+int dm_pci_find_capability(struct udevice *dev, int cap)
+{
+	u16 status;
+	u8 header_type;
+	int ttl = PCI_FIND_CAP_TTL;
+	u8 id;
+	u16 ent;
+	u8 pos;
+
+	dm_pci_read_config16(dev, PCI_STATUS, &status);
+	if (!(status & PCI_STATUS_CAP_LIST))
+		return 0;
+
+	dm_pci_read_config8(dev, PCI_HEADER_TYPE, &header_type);
+	if ((header_type & 0x7f) == PCI_HEADER_TYPE_CARDBUS)
+		pos = PCI_CB_CAPABILITY_LIST;
+	else
+		pos = PCI_CAPABILITY_LIST;
+
+	dm_pci_read_config8(dev, pos, &pos);
+	while (ttl--) {
+		if (pos < PCI_STD_HEADER_SIZEOF)
+			break;
+		pos &= ~3;
+		dm_pci_read_config16(dev, pos, &ent);
+
+		id = ent & 0xff;
+		if (id == 0xff)
+			break;
+		if (id == cap)
+			return pos;
+		pos = (ent >> 8);
+	}
+
+	return 0;
+}
+
+int dm_pci_find_ext_capability(struct udevice *dev, int cap)
+{
+	u32 header;
+	int ttl;
+	int pos = PCI_CFG_SPACE_SIZE;
+
+	/* minimum 8 bytes per capability */
+	ttl = (PCI_CFG_SPACE_EXP_SIZE - PCI_CFG_SPACE_SIZE) / 8;
+
+	dm_pci_read_config32(dev, pos, &header);
+	/*
+	 * If we have no capabilities, this is indicated by cap ID,
+	 * cap version and next pointer all being 0.
+	 */
+	if (header == 0)
+		return 0;
+
+	while (ttl--) {
+		if (PCI_EXT_CAP_ID(header) == cap)
+			return pos;
+
+		pos = PCI_EXT_CAP_NEXT(header);
+		if (pos < PCI_CFG_SPACE_SIZE)
+			break;
+
+		dm_pci_read_config32(dev, pos, &header);
+	}
+
+	return 0;
+}
+
 UCLASS_DRIVER(pci) = {
 	.id		= UCLASS_PCI,
 	.name		= "pci",

include/pci.h

@@ -17,6 +17,7 @@
  * Under PCI, each device has 256 bytes of configuration address space,
  * of which the first 64 bytes are standardized as follows:
  */
+#define PCI_STD_HEADER_SIZEOF	64
 #define PCI_VENDOR_ID		0x00	/* 16 bits */
 #define PCI_DEVICE_ID		0x02	/* 16 bits */
 #define PCI_COMMAND		0x04	/* 16 bits */
@@ -1311,6 +1312,51 @@ pci_addr_t dm_pci_phys_to_bus(struct udevice *dev, phys_addr_t addr,
  */
 void *dm_pci_map_bar(struct udevice *dev, int bar, int flags);
 
+/**
+ * dm_pci_find_capability() - find a capability
+ *
+ * Tell if a device supports a given PCI capability. Returns the
+ * address of the requested capability structure within the device's
+ * PCI configuration space or 0 in case the device does not support it.
+ *
+ * Possible values for @cap:
+ *
+ *  %PCI_CAP_ID_MSI	Message Signalled Interrupts
+ *  %PCI_CAP_ID_PCIX	PCI-X
+ *  %PCI_CAP_ID_EXP	PCI Express
+ *  %PCI_CAP_ID_MSIX	MSI-X
+ *
+ * See PCI_CAP_ID_xxx for the complete capability ID codes.
+ *
+ * @dev:	PCI device to query
+ * @cap:	capability code
+ * @return:	capability address or 0 if not supported
+ */
+int dm_pci_find_capability(struct udevice *dev, int cap);
+
+/**
+ * dm_pci_find_ext_capability() - find an extended capability
+ *
+ * Tell if a device supports a given PCI express extended capability.
+ * Returns the address of the requested extended capability structure
+ * within the device's PCI configuration space or 0 in case the device
+ * does not support it.
+ *
+ * Possible values for @cap:
+ *
+ *  %PCI_EXT_CAP_ID_ERR	Advanced Error Reporting
+ *  %PCI_EXT_CAP_ID_VC	Virtual Channel
+ *  %PCI_EXT_CAP_ID_DSN	Device Serial Number
+ *  %PCI_EXT_CAP_ID_PWR	Power Budgeting
+ *
+ * See PCI_EXT_CAP_ID_xxx for the complete extended capability ID codes.
+ *
+ * @dev:	PCI device to query
+ * @cap:	extended capability code
+ * @return:	extended capability address or 0 if not supported
+ */
+int dm_pci_find_ext_capability(struct udevice *dev, int cap);
+
 #define dm_pci_virt_to_bus(dev, addr, flags) \
 	dm_pci_phys_to_bus(dev, (virt_to_phys(addr)), (flags))
 #define dm_pci_bus_to_virt(dev, addr, flags, len, map_flags) \