From: Chen Yu <cheny...@huawei.com>

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 <xuw...@hisilicon.com>
Cc: Guodong Xu <guodong...@linaro.org>
Cc: Amit Pundir <amit.pun...@linaro.org>
Cc: Rob Herring <robh...@kernel.org>
Cc: John Youn <johny...@synopsys.com>
Cc: Douglas Anderson <diand...@chromium.org>
Cc: Chen Yu <cheny...@huawei.com>
Cc: Kishon Vijay Abraham I <kis...@ti.com>
Cc: Felipe Balbi <felipe.ba...@linux.intel.com>
Cc: Greg Kroah-Hartman <gre...@linuxfoundation.org>
Cc: linux-...@vger.kernel.org
Signed-off-by: Chen Yu <cheny...@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.stu...@linaro.org>
---
v2:
* Fix build issue reported by kbuildbot
* Rework to avoid using new dts entry suggested by RobH
* Further tweaks from Chen Yu to try to address comments from
  John Youn
* Further simplified logic
---
 drivers/usb/dwc2/core.h     |  6 +++++
 drivers/usb/dwc2/hcd.c      | 60 +++++++++++++++++++++++++++++++++++++++++++++
 drivers/usb/dwc2/platform.c |  1 +
 3 files changed, 67 insertions(+)

diff --git a/drivers/usb/dwc2/core.h b/drivers/usb/dwc2/core.h
index 963ea1b..de1fa0c 100644
--- a/drivers/usb/dwc2/core.h
+++ b/drivers/usb/dwc2/core.h
@@ -417,6 +417,11 @@ enum dwc2_ep0_state {
  *                     needed.
  *                     0 - No (default)
  *                     1 - Yes
+ * @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
@@ -457,6 +462,7 @@ struct dwc2_core_params {
        int uframe_sched;
        int external_id_pin_ctl;
        int hibernation;
+       int change_speed_quirk;
 };
 
 /**
diff --git a/drivers/usb/dwc2/hcd.c b/drivers/usb/dwc2/hcd.c
index 008f5bc..7cf8d8e 100644
--- a/drivers/usb/dwc2/hcd.c
+++ b/drivers/usb/dwc2/hcd.c
@@ -4873,6 +4873,61 @@ 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->core_params->speed == speed)
+               return;
+
+       hsotg->core_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->core_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->core_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",
@@ -5028,6 +5083,11 @@ int dwc2_hcd_init(struct dwc2_hsotg *hsotg, int irq)
                        dev_warn(hsotg->dev, "can't set coherent DMA mask\n");
        }
 
+       if (hsotg->core_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;
diff --git a/drivers/usb/dwc2/platform.c b/drivers/usb/dwc2/platform.c
index 8e1728b..17eb5fd 100644
--- a/drivers/usb/dwc2/platform.c
+++ b/drivers/usb/dwc2/platform.c
@@ -85,6 +85,7 @@ static const struct dwc2_core_params params_hi6220 = {
        .uframe_sched                   = 0,
        .external_id_pin_ctl            = -1,
        .hibernation                    = -1,
+       .change_speed_quirk             = 1,
 };
 
 static const struct dwc2_core_params params_bcm2835 = {
-- 
2.7.4

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