usb: dwc3: gadget: Check ENBLSLPM before sending ep command

Upstream Linux commit 87dd96111b0b.

When operating in USB 2.0 speeds (HS/FS), if GUSB2PHYCFG.ENBLSLPM or
GUSB2PHYCFG.SUSPHY is set, it must be cleared before issuing an endpoint
command.

Current implementation only save and restore GUSB2PHYCFG.SUSPHY
configuration. We must save and clear both GUSB2PHYCFG.ENBLSLPM and
GUSB2PHYCFG.SUSPHY settings. Restore them after the command is
completed.

DWC_usb3 3.30a and DWC_usb31 1.90a programming guide section 3.2.2

Signed-off-by: Thinh Nguyen <[email protected]>
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

@@ -300,26 +300,35 @@ int dwc3_send_gadget_ep_cmd(struct dwc3 *dwc, unsigned ep,
 		unsigned cmd, struct dwc3_gadget_ep_cmd_params *params)
 {
 	u32			timeout = 500;
+	u32			saved_config = 0;
 	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.
+	 * When operating in USB 2.0 speeds (HS/FS), if GUSB2PHYCFG.ENBLSLPM or
+	 * GUSB2PHYCFG.SUSPHY is set, it must be cleared before issuing an
+	 * endpoint command.
 	 *
-	 * We will also set SUSPHY bit to what it was before returning as stated
-	 * by the same section on Synopsys databook.
+	 * Save and clear both GUSB2PHYCFG.ENBLSLPM and GUSB2PHYCFG.SUSPHY
+	 * settings. Restore them after the command is completed.
+	 *
+	 * DWC_usb3 3.30a and DWC_usb31 1.90a programming guide section 3.2.2
 	 */
 	if (dwc->gadget.speed <= USB_SPEED_HIGH) {
 		reg = dwc3_readl(dwc->regs, DWC3_GUSB2PHYCFG(0));
 		if (unlikely(reg & DWC3_GUSB2PHYCFG_SUSPHY)) {
-			susphy = true;
+			saved_config |= DWC3_GUSB2PHYCFG_SUSPHY;
 			reg &= ~DWC3_GUSB2PHYCFG_SUSPHY;
-			dwc3_writel(dwc->regs, DWC3_GUSB2PHYCFG(0), reg);
 		}
+
+		if (reg & DWC3_GUSB2PHYCFG_ENBLSLPM) {
+			saved_config |= DWC3_GUSB2PHYCFG_ENBLSLPM;
+			reg &= ~DWC3_GUSB2PHYCFG_ENBLSLPM;
+		}
+
+		if (saved_config)
+			dwc3_writel(dwc->regs, DWC3_GUSB2PHYCFG(0), reg);
 	}
 
 	dwc3_writel(dwc->regs, DWC3_DEPCMDPAR0(ep), params->param0);
@@ -349,9 +358,9 @@ int dwc3_send_gadget_ep_cmd(struct dwc3 *dwc, unsigned ep,
 		udelay(1);
 	} while (1);
 
-	if (unlikely(susphy)) {
+	if (saved_config) {
 		reg = dwc3_readl(dwc->regs, DWC3_GUSB2PHYCFG(0));
-		reg |= DWC3_GUSB2PHYCFG_SUSPHY;
+		reg |= saved_config;
 		dwc3_writel(dwc->regs, DWC3_GUSB2PHYCFG(0), reg);
 	}