[PATCH v3] usb: dwc3: core: Do core softreset when switch mode

[Thinh Nguyen <Thinh.Nguyen@synopsys.com>]

From: Yu Chen <chenyu56@huawei.com>
From: John Stultz <john.stultz@linaro.org>

According to the programming guide, to switch mode for DRD controller,
the driver needs to do the following.

To switch from device to host:
1. Reset controller with GCTL.CoreSoftReset
2. Set GCTL.PrtCapDir(host mode)
3. Reset the host with USBCMD.HCRESET
4. Then follow up with the initializing host registers sequence

To switch from host to device:
1. Reset controller with GCTL.CoreSoftReset
2. Set GCTL.PrtCapDir(device mode)
3. Reset the device with DCTL.CSftRst
4. Then follow up with the initializing registers sequence

Currently we're missing step 1) to do GCTL.CoreSoftReset and step 3) of
switching from host to device. John Stult reported a lockup issue seen
with HiKey960 platform without these steps[1]. Similar issue is observed
with Ferry's testing platform[2].

So, apply the required steps along with some fixes to Yu Chen's and John
Stultz's version. The main fixes to their versions are the missing wait
for clocks synchronization before clearing GCTL.CoreSoftReset and only
apply DCTL.CSftRst when switching from host to device.

[1] https://lore.kernel.org/linux-usb/20210108015115.27920-1-john.stultz@linaro.org/
[2] https://lore.kernel.org/linux-usb/0ba7a6ba-e6a7-9cd4-0695-64fc927e01f1@gmail.com/

Cc: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: Ferry Toth <fntoth@gmail.com>
Cc: Wesley Cheng <wcheng@codeaurora.org>
Cc: <stable@vger.kernel.org>
Fixes: 41ce1456e1db ("usb: dwc3: core: make dwc3_set_mode() work properly")
Signed-off-by: Yu Chen <chenyu56@huawei.com>
Signed-off-by: John Stultz <john.stultz@linaro.org>
Signed-off-by: Thinh Nguyen <Thinh.Nguyen@synopsys.com>
---
Changes in v3:
- Check if the desired mode is OTG, then keep the old flow
- Remove condition for OTG support only since the device can still be
  configured DRD host/device mode only
- Remove redundant hw_mode check since __dwc3_set_mode() only applies when
  hw_mode is DRD
Changes in v2:
- Initialize mutex per device and not as global mutex.
- Add additional checks for DRD only mode

 drivers/usb/dwc3/core.c | 27 +++++++++++++++++++++++++++
 drivers/usb/dwc3/core.h |  5 +++++
 2 files changed, 32 insertions(+)

diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
index 5c25e6a72dbd..2f118ad43571 100644
--- a/drivers/usb/dwc3/core.c
+++ b/drivers/usb/dwc3/core.c
@@ -114,6 +114,8 @@ void dwc3_set_prtcap(struct dwc3 *dwc, u32 mode)
 	dwc->current_dr_role = mode;
 }
 
+static int dwc3_core_soft_reset(struct dwc3 *dwc);
+
 static void __dwc3_set_mode(struct work_struct *work)
 {
 	struct dwc3 *dwc = work_to_dwc(work);
@@ -121,6 +123,8 @@ static void __dwc3_set_mode(struct work_struct *work)
 	int ret;
 	u32 reg;
 
+	mutex_lock(&dwc->mutex);
+
 	pm_runtime_get_sync(dwc->dev);
 
 	if (dwc->current_dr_role == DWC3_GCTL_PRTCAP_OTG)
@@ -154,6 +158,25 @@ static void __dwc3_set_mode(struct work_struct *work)
 		break;
 	}
 
+	/* For DRD host or device mode only */
+	if (dwc->desired_dr_role != DWC3_GCTL_PRTCAP_OTG) {
+		reg = dwc3_readl(dwc->regs, DWC3_GCTL);
+		reg |= DWC3_GCTL_CORESOFTRESET;
+		dwc3_writel(dwc->regs, DWC3_GCTL, reg);
+
+		/*
+		 * Wait for internal clocks to synchronized. DWC_usb31 and
+		 * DWC_usb32 may need at least 50ms (less for DWC_usb3). To
+		 * keep it consistent across different IPs, let's wait up to
+		 * 100ms before clearing GCTL.CORESOFTRESET.
+		 */
+		msleep(100);
+
+		reg = dwc3_readl(dwc->regs, DWC3_GCTL);
+		reg &= ~DWC3_GCTL_CORESOFTRESET;
+		dwc3_writel(dwc->regs, DWC3_GCTL, reg);
+	}
+
 	spin_lock_irqsave(&dwc->lock, flags);
 
 	dwc3_set_prtcap(dwc, dwc->desired_dr_role);
@@ -178,6 +201,8 @@ static void __dwc3_set_mode(struct work_struct *work)
 		}
 		break;
 	case DWC3_GCTL_PRTCAP_DEVICE:
+		dwc3_core_soft_reset(dwc);
+
 		dwc3_event_buffers_setup(dwc);
 
 		if (dwc->usb2_phy)
@@ -200,6 +225,7 @@ static void __dwc3_set_mode(struct work_struct *work)
 out:
 	pm_runtime_mark_last_busy(dwc->dev);
 	pm_runtime_put_autosuspend(dwc->dev);
+	mutex_unlock(&dwc->mutex);
 }
 
 void dwc3_set_mode(struct dwc3 *dwc, u32 mode)
@@ -1553,6 +1579,7 @@ static int dwc3_probe(struct platform_device *pdev)
 	dwc3_cache_hwparams(dwc);
 
 	spin_lock_init(&dwc->lock);
+	mutex_init(&dwc->mutex);
 
 	pm_runtime_set_active(dev);
 	pm_runtime_use_autosuspend(dev);
diff --git a/drivers/usb/dwc3/core.h b/drivers/usb/dwc3/core.h
index 695ff2d791e4..7e3afa5378e8 100644
--- a/drivers/usb/dwc3/core.h
+++ b/drivers/usb/dwc3/core.h
@@ -13,6 +13,7 @@
 
 #include <linux/device.h>
 #include <linux/spinlock.h>
+#include <linux/mutex.h>
 #include <linux/ioport.h>
 #include <linux/list.h>
 #include <linux/bitops.h>
@@ -947,6 +948,7 @@ struct dwc3_scratchpad_array {
  * @scratch_addr: dma address of scratchbuf
  * @ep0_in_setup: one control transfer is completed and enter setup phase
  * @lock: for synchronizing
+ * @mutex: for mode switching
  * @dev: pointer to our struct device
  * @sysdev: pointer to the DMA-capable device
  * @xhci: pointer to our xHCI child
@@ -1088,6 +1090,9 @@ struct dwc3 {
 	/* device lock */
 	spinlock_t		lock;
 
+	/* mode switching lock */
+	struct mutex		mutex;
+
 	struct device		*dev;
 	struct device		*sysdev;
 

base-commit: 4b853c236c7b5161a2e444bd8b3c76fe5aa5ddcb
-- 
2.28.0