usb: dwc3: gadget: allow clock gating to work

The dwc3 core has internal clock gating support.

Let's allow that to happen by clearing the disable
bit in GCTL register.
Signed-off-by: NFelipe Balbi <balbi@ti.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

drivers/usb/dwc3/core.h

@@ -161,6 +161,7 @@
 #define DWC3_GCTL_CORESOFTRESET	(1 << 11)
 #define DWC3_GCTL_SCALEDOWN(n)	(n << 4)
 #define DWC3_GCTL_DISSCRAMBLE	(1 << 3)
+#define DWC3_GCTL_DSBLCLKGTNG	(1 << 0)
 
 /* Global USB2 PHY Configuration Register */
 #define DWC3_GUSB2PHYCFG_PHYSOFTRST (1 << 31)
@@ -170,6 +171,11 @@
 #define DWC3_GUSB3PIPECTL_PHYSOFTRST (1 << 31)
 #define DWC3_GUSB3PIPECTL_SUSPHY (1 << 17)
 
+/* Global HWPARAMS1 Register */
+#define DWC3_GHWPARAMS1_EN_PWROPT(n)	((n & (3 << 24)) >> 24)
+#define DWC3_GHWPARAMS1_EN_PWROPT_NO	0
+#define DWC3_GHWPARAMS1_EN_PWROPT_CLK	1
+
 /* Device Configuration Register */
 #define DWC3_DCFG_DEVADDR(addr)	((addr) << 3)
 #define DWC3_DCFG_DEVADDR_MASK	DWC3_DCFG_DEVADDR(0x7f)

drivers/usb/dwc3/gadget.c

@@ -1164,6 +1164,14 @@ static int dwc3_gadget_start(struct usb_gadget *g,
 	reg &= ~DWC3_GCTL_DISSCRAMBLE;
 	reg |= DWC3_GCTL_PRTCAPDIR(DWC3_GCTL_PRTCAP_DEVICE);
 
+	switch (DWC3_GHWPARAMS1_EN_PWROPT(dwc->hwparams.hwparams0)) {
+	case DWC3_GHWPARAMS1_EN_PWROPT_CLK:
+		reg &= ~DWC3_GCTL_DSBLCLKGTNG;
+		break;
+	default:
+		dev_dbg(dwc->dev, "No power optimization available\n");
+	}
+
 	/*
 	 * WORKAROUND: DWC3 revisions <1.90a have a bug
 	 * when The device fails to connect at SuperSpeed