usb: dwc2: Don't reset the core after setting turnaround time

Every time the hub signals a reset while we (device) are hsotg->connected,
dwc2_hsotg_core_init_disconnected() is called, which in turn calls
dwc2_hs_phy_init().

GUSBCFG.USBTrdTim is cleared upon Core Soft Reset, so if
hsotg->params.phy_utmi_width is 8-bit, the value of GUSBCFG.USBTrdTim (the
default one: 0x5, corresponding to 16-bit) is always different from
hsotg->params.phy_utmi_width, thus dwc2_core_reset() is called every
time (usbcfg != usbcfg_old), which causes 2 issues:

1) The call to dwc2_core_reset() does another reset 300us after the initial
Chirp K of the first reset (which should last at least Tuch = 1ms), and
messes up the High-speed Detection Handshake: both hub and device drive
current into the D+ and D- lines at the same time.

2) GUSBCFG.USBTrdTim is cleared by the second reset, so its value is always
the default one (0x5).

Setting GUSBCFG.USBTrdTim after the potential call to dwc2_core_reset()
fixes both issues.  It is now set even when select_phy is false because the
cost of the Core Soft Reset is removed.

Fixes: 1e868545 ("usb: dwc2: gadget: Move gadget phy init into core phy init")
Signed-off-by: Clément Lassieur <clement@lassieur.org>
Link: https://lore.kernel.org/r/20210603155921.940651-1-clement@lassieur.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/dwc2/core.c

@@ -1111,15 +1111,6 @@ static int dwc2_hs_phy_init(struct dwc2_hsotg *hsotg, bool select_phy)
 		usbcfg &= ~(GUSBCFG_ULPI_UTMI_SEL | GUSBCFG_PHYIF16);
 		if (hsotg->params.phy_utmi_width == 16)
 			usbcfg |= GUSBCFG_PHYIF16;
-
-		/* Set turnaround time */
-		if (dwc2_is_device_mode(hsotg)) {
-			usbcfg &= ~GUSBCFG_USBTRDTIM_MASK;
-			if (hsotg->params.phy_utmi_width == 16)
-				usbcfg |= 5 << GUSBCFG_USBTRDTIM_SHIFT;
-			else
-				usbcfg |= 9 << GUSBCFG_USBTRDTIM_SHIFT;
-		}
 		break;
 	default:
 		dev_err(hsotg->dev, "FS PHY selected at HS!\n");
@@ -1141,6 +1132,24 @@ static int dwc2_hs_phy_init(struct dwc2_hsotg *hsotg, bool select_phy)
 	return retval;
 }
 
+static void dwc2_set_turnaround_time(struct dwc2_hsotg *hsotg)
+{
+	u32 usbcfg;
+
+	if (hsotg->params.phy_type != DWC2_PHY_TYPE_PARAM_UTMI)
+		return;
+
+	usbcfg = dwc2_readl(hsotg, GUSBCFG);
+
+	usbcfg &= ~GUSBCFG_USBTRDTIM_MASK;
+	if (hsotg->params.phy_utmi_width == 16)
+		usbcfg |= 5 << GUSBCFG_USBTRDTIM_SHIFT;
+	else
+		usbcfg |= 9 << GUSBCFG_USBTRDTIM_SHIFT;
+
+	dwc2_writel(hsotg, usbcfg, GUSBCFG);
+}
+
 int dwc2_phy_init(struct dwc2_hsotg *hsotg, bool select_phy)
 {
 	u32 usbcfg;
@@ -1158,6 +1167,9 @@ int dwc2_phy_init(struct dwc2_hsotg *hsotg, bool select_phy)
 		retval = dwc2_hs_phy_init(hsotg, select_phy);
 		if (retval)
 			return retval;
+
+		if (dwc2_is_device_mode(hsotg))
+			dwc2_set_turnaround_time(hsotg);
 	}
 
 	if (hsotg->hw_params.hs_phy_type == GHWCFG2_HS_PHY_TYPE_ULPI &&