usb: dwc2: Change TxFIFO and RxFIFO flushing flow

Before flushing fifos required to check AHB master state and
lush when AHB master is in IDLE state.
Acked-by: John Youn <johnyoun@synopsys.com>
Signed-off-by: Minas Harutyunyan <hminas@synopsys.com>
Signed-off-by: Grigor Tovmasyan <tovmasya@synopsys.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

drivers/usb/dwc2/core.c

@@ -675,6 +675,11 @@ void dwc2_flush_tx_fifo(struct dwc2_hsotg *hsotg, const int num)
 
 	dev_vdbg(hsotg->dev, "Flush Tx FIFO %d\n", num);
 
+	/* Wait for AHB master IDLE state */
+	if (dwc2_hsotg_wait_bit_set(hsotg, GRSTCTL, GRSTCTL_AHBIDLE, 10000))
+		dev_warn(hsotg->dev, "%s:  HANG! AHB Idle GRSCTL\n",
+			 __func__);
+
 	greset = GRSTCTL_TXFFLSH;
 	greset |= num << GRSTCTL_TXFNUM_SHIFT & GRSTCTL_TXFNUM_MASK;
 	dwc2_writel(greset, hsotg->regs + GRSTCTL);
@@ -698,6 +703,11 @@ void dwc2_flush_rx_fifo(struct dwc2_hsotg *hsotg)
 
 	dev_vdbg(hsotg->dev, "%s()\n", __func__);
 
+	/* Wait for AHB master IDLE state */
+	if (dwc2_hsotg_wait_bit_set(hsotg, GRSTCTL, GRSTCTL_AHBIDLE, 10000))
+		dev_warn(hsotg->dev, "%s:  HANG! AHB Idle GRSCTL\n",
+			 __func__);
+
 	greset = GRSTCTL_RXFFLSH;
 	dwc2_writel(greset, hsotg->regs + GRSTCTL);