usb: chipidea: add identification registers access APIs

Using hw_write_id_reg and hw_read_id_reg to write and read identification
registers contents, they can be used to get controller information, change
some system configurations, and so on.

Reviewed-by: Stefan Agner <[e-mail]>
Signed-off-by: Peter Chen <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/usb/chipidea/ci.h

···
 /******************************************************************************
  * REGISTERS
  *****************************************************************************/
+/* Identification Registers */
+#define ID_ID				0x0
+#define ID_HWGENERAL			0x4
+#define ID_HWHOST			0x8
+#define ID_HWDEVICE			0xc
+#define ID_HWTXBUF			0x10
+#define ID_HWRXBUF			0x14
+#define ID_SBUSCFG			0x90
+
 /* register indices */
 enum ci_hw_regs {
 	CAP_CAPLENGTH,
···
 	ci->role = CI_ROLE_END;
 
 	ci->roles[role]->stop(ci);
+}
+
+/**
+ * hw_read_id_reg: reads from a identification register
+ * @ci: the controller
+ * @offset: offset from the beginning of identification registers region
+ * @mask: bitfield mask
+ *
+ * This function returns register contents
+ */
+static inline u32 hw_read_id_reg(struct ci_hdrc *ci, u32 offset, u32 mask)
+{
+	return ioread32(ci->hw_bank.abs + offset) & mask;
+}
+
+/**
+ * hw_write_id_reg: writes to a identification register
+ * @ci: the controller
+ * @offset: offset from the beginning of identification registers region
+ * @mask: bitfield mask
+ * @data: new value
+ */
+static inline void hw_write_id_reg(struct ci_hdrc *ci, u32 offset,
+			    u32 mask, u32 data)
+{
+	if (~mask)
+		data = (ioread32(ci->hw_bank.abs + offset) & ~mask)
+			| (data & mask);
+
+	iowrite32(data, ci->hw_bank.abs + offset);
 }
 
 /**