usb: dwc2: Add a quirk to allow speed negotiation for Hisilicon Hi6220

The Hi6220's usb controller is limited in that it does not
support "Split Transactions", so it does not support communicating
with low-speed and full-speed devices behind a high-speed hub.

Thus it requires a quirk so that we can manually drop the usb
speed when low/full-speed are attached, and bump back to high
speed when they are removed.

Cc: Wei Xu <xuwei5@hisilicon.com>
Cc: Guodong Xu <guodong.xu@linaro.org>
Cc: Amit Pundir <amit.pundir@linaro.org>
Cc: Rob Herring <robh+dt@kernel.org>
Cc: John Youn <johnyoun@synopsys.com>
Cc: Douglas Anderson <dianders@chromium.org>
Cc: Chen Yu <chenyu56@huawei.com>
Cc: Vardan Mikayelyan <mvardan@synopsys.com>
Cc: Kishon Vijay Abraham I <kishon@ti.com>
Cc: Felipe Balbi <felipe.balbi@linux.intel.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: linux-usb@vger.kernel.org
Signed-off-by: Chen Yu <chenyu56@huawei.com>
[jstultz: Reworked to simplify the patch, and made
 commit log to be more specific about the issue]
Signed-off-by: John Stultz <john.stultz@linaro.org>
Signed-off-by: John Youn <johnyoun@synopsys.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

drivers/usb/dwc2/core.h

@@ -444,6 +444,11 @@ enum dwc2_ep0_state {
  *			in DWORDS with possible values from from
  *			16-32768 (default: 256, 256, 256, 256, 768,
  *			768, 768, 768, 0, 0, 0, 0, 0, 0, 0).
+ * @change_speed_quirk: Change speed configuration to DWC2_SPEED_PARAM_FULL
+ *                      while full&low speed device connect. And change speed
+ *                      back to DWC2_SPEED_PARAM_HIGH while device is gone.
+ *			0 - No (default)
+ *			1 - Yes
  *
  * The following parameters may be specified when starting the module. These
  * parameters define how the DWC_otg controller should be configured. A
@@ -501,6 +506,8 @@ struct dwc2_core_params {
 	u32 g_rx_fifo_size;
 	u32 g_np_tx_fifo_size;
 	u32 g_tx_fifo_size[MAX_EPS_CHANNELS];
+
+	bool change_speed_quirk;
 };
 
 /**

drivers/usb/dwc2/hcd.c

@@ -4868,6 +4868,61 @@ static void _dwc2_hcd_clear_tt_buffer_complete(struct usb_hcd *hcd,
 	spin_unlock_irqrestore(&hsotg->lock, flags);
 }
 
+/*
+ * HPRT0_SPD_HIGH_SPEED: high speed
+ * HPRT0_SPD_FULL_SPEED: full speed
+ */
+static void dwc2_change_bus_speed(struct usb_hcd *hcd, int speed)
+{
+	struct dwc2_hsotg *hsotg = dwc2_hcd_to_hsotg(hcd);
+
+	if (hsotg->params.speed == speed)
+		return;
+
+	hsotg->params.speed = speed;
+	queue_work(hsotg->wq_otg, &hsotg->wf_otg);
+}
+
+static void dwc2_free_dev(struct usb_hcd *hcd, struct usb_device *udev)
+{
+	struct dwc2_hsotg *hsotg = dwc2_hcd_to_hsotg(hcd);
+
+	if (!hsotg->params.change_speed_quirk)
+		return;
+
+	/*
+	 * On removal, set speed to default high-speed.
+	 */
+	if (udev->parent && udev->parent->speed > USB_SPEED_UNKNOWN &&
+	    udev->parent->speed < USB_SPEED_HIGH) {
+		dev_info(hsotg->dev, "Set speed to default high-speed\n");
+		dwc2_change_bus_speed(hcd, HPRT0_SPD_HIGH_SPEED);
+	}
+}
+
+static int dwc2_reset_device(struct usb_hcd *hcd, struct usb_device *udev)
+{
+	struct dwc2_hsotg *hsotg = dwc2_hcd_to_hsotg(hcd);
+
+	if (!hsotg->params.change_speed_quirk)
+		return 0;
+
+	if (udev->speed == USB_SPEED_HIGH) {
+		dev_info(hsotg->dev, "Set speed to high-speed\n");
+		dwc2_change_bus_speed(hcd, HPRT0_SPD_HIGH_SPEED);
+	} else if ((udev->speed == USB_SPEED_FULL ||
+				udev->speed == USB_SPEED_LOW)) {
+		/*
+		 * Change speed setting to full-speed if there's
+		 * a full-speed or low-speed device plugged in.
+		 */
+		dev_info(hsotg->dev, "Set speed to full-speed\n");
+		dwc2_change_bus_speed(hcd, HPRT0_SPD_FULL_SPEED);
+	}
+
+	return 0;
+}
+
 static struct hc_driver dwc2_hc_driver = {
 	.description = "dwc2_hsotg",
 	.product_desc = "DWC OTG Controller",
@@ -5023,6 +5078,11 @@ int dwc2_hcd_init(struct dwc2_hsotg *hsotg, int irq)
 			dev_warn(hsotg->dev, "can't set coherent DMA mask\n");
 	}
 
+	if (hsotg->params.change_speed_quirk) {
+		dwc2_hc_driver.free_dev = dwc2_free_dev;
+		dwc2_hc_driver.reset_device = dwc2_reset_device;
+	}
+
 	hcd = usb_create_hcd(&dwc2_hc_driver, hsotg->dev, dev_name(hsotg->dev));
 	if (!hcd)
 		goto error1;

drivers/usb/dwc2/params.c

@@ -68,6 +68,7 @@ static void dwc2_set_his_params(struct dwc2_hsotg *hsotg)
 	p->ahbcfg = GAHBCFG_HBSTLEN_INCR16 <<
 		GAHBCFG_HBSTLEN_SHIFT;
 	p->uframe_sched = false;
+	p->change_speed_quirk = true;
 }
 
 static void dwc2_set_rk_params(struct dwc2_hsotg *hsotg)