[PATCH v2 1/4] usb: dwc3: gadget: Don't send unintended link state change

[Thinh Nguyen <Thinh.Nguyen@xxxxxxxxxxxx>]

DCTL.ULSTCHNGREQ is a write-only field. When doing a read-modify-write
to DCTL, the driver must make sure that there's no unintended link state
change request from whatever is read from DCTL.ULSTCHNGREQ. Set link
state change to no-action when the driver writes to DCTL.

Signed-off-by: Thinh Nguyen <thinhn@xxxxxxxxxxxx>
---

Changes in v2:
 - Create inline function to do safe write to DCTL

 drivers/usb/dwc3/gadget.c | 16 +++++++---------
 drivers/usb/dwc3/gadget.h | 14 ++++++++++++++
 2 files changed, 21 insertions(+), 9 deletions(-)

diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
index 86dc1db788a9..85adc718808a 100644
--- a/drivers/usb/dwc3/gadget.c
+++ b/drivers/usb/dwc3/gadget.c
@@ -57,7 +57,7 @@ int dwc3_gadget_set_test_mode(struct dwc3 *dwc, int mode)
 		return -EINVAL;
 	}
 
-	dwc3_writel(dwc->regs, DWC3_DCTL, reg);
+	dwc3_gadget_dctl_write_safe(dwc, reg);
 
 	return 0;
 }
@@ -1822,7 +1822,7 @@ static int dwc3_gadget_run_stop(struct dwc3 *dwc, int is_on, int suspend)
 		dwc->pullups_connected = false;
 	}
 
-	dwc3_writel(dwc->regs, DWC3_DCTL, reg);
+	dwc3_gadget_dctl_write_safe(dwc, reg);
 
 	do {
 		reg = dwc3_readl(dwc->regs, DWC3_DSTS);
@@ -2745,10 +2745,8 @@ static void dwc3_gadget_disconnect_interrupt(struct dwc3 *dwc)
 
 	reg = dwc3_readl(dwc->regs, DWC3_DCTL);
 	reg &= ~DWC3_DCTL_INITU1ENA;
-	dwc3_writel(dwc->regs, DWC3_DCTL, reg);
-
 	reg &= ~DWC3_DCTL_INITU2ENA;
-	dwc3_writel(dwc->regs, DWC3_DCTL, reg);
+	dwc3_gadget_dctl_write_safe(dwc, reg);
 
 	dwc3_disconnect_gadget(dwc);
 
@@ -2800,7 +2798,7 @@ static void dwc3_gadget_reset_interrupt(struct dwc3 *dwc)
 
 	reg = dwc3_readl(dwc->regs, DWC3_DCTL);
 	reg &= ~DWC3_DCTL_TSTCTRL_MASK;
-	dwc3_writel(dwc->regs, DWC3_DCTL, reg);
+	dwc3_gadget_dctl_write_safe(dwc, reg);
 	dwc->test_mode = false;
 	dwc3_clear_stall_all_ep(dwc);
 
@@ -2904,11 +2902,11 @@ static void dwc3_gadget_conndone_interrupt(struct dwc3 *dwc)
 		if (dwc->has_lpm_erratum && dwc->revision >= DWC3_REVISION_240A)
 			reg |= DWC3_DCTL_NYET_THRES(dwc->lpm_nyet_threshold);
 
-		dwc3_writel(dwc->regs, DWC3_DCTL, reg);
+		dwc3_gadget_dctl_write_safe(dwc, reg);
 	} else {
 		reg = dwc3_readl(dwc->regs, DWC3_DCTL);
 		reg &= ~DWC3_DCTL_HIRD_THRES_MASK;
-		dwc3_writel(dwc->regs, DWC3_DCTL, reg);
+		dwc3_gadget_dctl_write_safe(dwc, reg);
 	}
 
 	dep = dwc->eps[0];
@@ -3017,7 +3015,7 @@ static void dwc3_gadget_linksts_change_interrupt(struct dwc3 *dwc,
 
 				reg &= ~u1u2;
 
-				dwc3_writel(dwc->regs, DWC3_DCTL, reg);
+				dwc3_gadget_dctl_write_safe(dwc, reg);
 				break;
 			default:
 				/* do nothing */
diff --git a/drivers/usb/dwc3/gadget.h b/drivers/usb/dwc3/gadget.h
index 5faf4d1249e0..fbc7d8013f0b 100644
--- a/drivers/usb/dwc3/gadget.h
+++ b/drivers/usb/dwc3/gadget.h
@@ -127,4 +127,18 @@ static inline void dwc3_gadget_ep_get_transfer_index(struct dwc3_ep *dep)
 	dep->resource_index = DWC3_DEPCMD_GET_RSC_IDX(res_id);
 }
 
+/**
+ * dwc3_gadget_dctl_write_safe - write to DCTL safe from link state change
+ * @dwc: pointer to our context structure
+ * @value: value to write to DCTL
+ *
+ * Use this function when doing read-modify-write to DCTL. It will not
+ * send link state change request.
+ */
+static inline void dwc3_gadget_dctl_write_safe(struct dwc3 *dwc, u32 value)
+{
+	value &= ~DWC3_DCTL_ULSTCHNGREQ_MASK;
+	dwc3_writel(dwc->regs, DWC3_DCTL, value);
+}
+
 #endif /* __DRIVERS_USB_DWC3_GADGET_H */
-- 
2.11.0