usb: dwc3: gadget: clear SUSPHY bit before ep cmds

Upstream Linux commit 2b0f11df84bb.

Synopsys Databook 2.60a has a note that if we're
sending an endpoint command we _must_ make sure that
DWC3_GUSB2PHY(n).SUSPHY bit is cleared.

This patch implements that particular detail.

Signed-off-by: Felipe Balbi <[email protected]>
Signed-off-by: Alexander Sverdlin <[email protected]>
Reviewed-by: Mattijs Korpershoek <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Mattijs Korpershoek <[email protected]>

drivers/usb/dwc3/gadget.c

@@ -301,8 +301,25 @@ int dwc3_send_gadget_ep_cmd(struct dwc3 *dwc, unsigned ep,
 {
 	u32			timeout = 500;
 	u32			reg;
+
+	int			susphy = false;
 	int			ret = -EINVAL;
 
+	/*
+	 * Synopsys Databook 2.60a states, on section 6.3.2.5.[1-8], that if
+	 * we're issuing an endpoint command, we must check if
+	 * GUSB2PHYCFG.SUSPHY bit is set. If it is, then we need to clear it.
+	 *
+	 * We will also set SUSPHY bit to what it was before returning as stated
+	 * by the same section on Synopsys databook.
+	 */
+	reg = dwc3_readl(dwc->regs, DWC3_GUSB2PHYCFG(0));
+	if (unlikely(reg & DWC3_GUSB2PHYCFG_SUSPHY)) {
+		susphy = true;
+		reg &= ~DWC3_GUSB2PHYCFG_SUSPHY;
+		dwc3_writel(dwc->regs, DWC3_GUSB2PHYCFG(0), reg);
+	}
+
 	dwc3_writel(dwc->regs, DWC3_DEPCMDPAR0(ep), params->param0);
 	dwc3_writel(dwc->regs, DWC3_DEPCMDPAR1(ep), params->param1);
 	dwc3_writel(dwc->regs, DWC3_DEPCMDPAR2(ep), params->param2);
@@ -330,6 +347,12 @@ int dwc3_send_gadget_ep_cmd(struct dwc3 *dwc, unsigned ep,
 		udelay(1);
 	} while (1);
 
+	if (unlikely(susphy)) {
+		reg = dwc3_readl(dwc->regs, DWC3_GUSB2PHYCFG(0));
+		reg |= DWC3_GUSB2PHYCFG_SUSPHY;
+		dwc3_writel(dwc->regs, DWC3_GUSB2PHYCFG(0), reg);
+	}
+
 	return ret;
 }