drivers: udc_dwc2: Add option to prefer 8-bit UTMI interface

The UDC DWC2 may support both 8- and 16-bit UTMI+ PHY interface widths.
Added a Kconfig option that allows the user to prefer 8-bit interface
width, if the hardware supports it.

Signed-off-by: Rafał Kuźnia <[email protected]>

Author: e-rk

drivers/usb/common/usb_dwc2_hw.h

@@ -486,6 +486,9 @@ USB_DWC2_GET_FIELD_DEFINE(ghwcfg3_xfersizewidth, GHWCFG3_XFERSIZEWIDTH)
 #define USB_DWC2_GHWCFG4_NUMCTLEPS_MASK		(0xFUL << USB_DWC2_GHWCFG4_NUMCTLEPS_POS)
 #define USB_DWC2_GHWCFG4_PHYDATAWIDTH_POS	14UL
 #define USB_DWC2_GHWCFG4_PHYDATAWIDTH_MASK	(0x3UL << USB_DWC2_GHWCFG4_PHYDATAWIDTH_POS)
+#define USB_DWC2_GHWCFG4_PHYDATAWIDTH_8_BIT	0UL
+#define USB_DWC2_GHWCFG4_PHYDATAWIDTH_16_BIT	1UL
+#define USB_DWC2_GHWCFG4_PHYDATAWIDTH_8_16_BIT	2UL
 #define USB_DWC2_GHWCFG4_ENHANCEDLPMSUPT_POS	13UL
 #define USB_DWC2_GHWCFG4_ENHANCEDLPMSUPT	BIT(USB_DWC2_GHWCFG4_ENHANCEDLPMSUPT_POS)
 #define USB_DWC2_GHWCFG4_ACGSUPT_POS		12UL

drivers/usb/udc/Kconfig.dwc2

@@ -48,3 +48,11 @@ config UDC_DWC2_USBHS_VBUS_READY_TIMEOUT
 	  UDC DWC2 USBHS VBUS ready event timeout. If the VBUS is not ready
 	  and the Nordic USBHS controller is used, the udc_enable() is
 	  blocked for this amount of time. Set it to zero to wait forever.
+
+config UDC_DWC2_PREFER_8BIT_UTMI
+	bool "Prefer 8-bit UTMI+ PHY interface width"
+	depends on UDC_DWC2
+	help
+	  UDC DWC2 may support both 8- and 16-bit UTMI+ PHY interface widths.
+	  Enable this config to prefer 8-bit interface. Otherwise 16-bit interface
+	  will be used.

drivers/usb/udc/udc_dwc2.c

@@ -1895,7 +1895,10 @@ static int udc_dwc2_init_controller(const struct device *dev)
 		hs_phy = false;
 	}
 
-	if (usb_dwc2_get_ghwcfg4_phydatawidth(ghwcfg4)) {
+	if (IS_ENABLED(CONFIG_UDC_DWC2_PREFER_8BIT_UTMI) &&
+	    usb_dwc2_get_ghwcfg4_phydatawidth(ghwcfg4) == USB_DWC2_GHWCFG4_PHYDATAWIDTH_8_16_BIT) {
+		LOG_DBG("Using 8-bit UTMI+");
+	} else if (usb_dwc2_get_ghwcfg4_phydatawidth(ghwcfg4)) {
 		gusbcfg |= USB_DWC2_GUSBCFG_PHYIF_16_BIT;
 	}