usb: dwc2: add helper function for setting SPLIT HC registers

The split register setting is used for both SSPLIT and CSPLIT transactions,
the bit for CSPLIT has to be set seperately.

Signed-off-by: Stefan Brüns <stefan.bruens@rwth-aachen.de>
diff --git a/drivers/usb/host/dwc2.c b/drivers/usb/host/dwc2.c
index 0e710d9..7fbbc4b 100644
--- a/drivers/usb/host/dwc2.c
+++ b/drivers/usb/host/dwc2.c
@@ -432,10 +432,23 @@
 	 */
 	writel(hcchar, &hc_regs->hcchar);
 
-	/* Program the HCSPLIT register for SPLITs */
+	/* Program the HCSPLIT register, default to no SPLIT */
 	writel(0, &hc_regs->hcsplt);
 }
 
+static void dwc_otg_hc_init_split(struct dwc2_hc_regs *hc_regs,
+				  uint8_t hub_devnum, uint8_t hub_port)
+{
+	uint32_t hcsplt = 0;
+
+	hcsplt = DWC2_HCSPLT_SPLTENA;
+	hcsplt |= hub_devnum << DWC2_HCSPLT_HUBADDR_OFFSET;
+	hcsplt |= hub_port << DWC2_HCSPLT_PRTADDR_OFFSET;
+
+	/* Program the HCSPLIT register for SPLITs */
+	writel(hcsplt, &hc_regs->hcsplt);
+}
+
 /*
  * DWC2 to USB API interface
  */