usb: dwc3: gadget: Don't send unintended link state change

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.

Note that this patch was submitted upstream in Linux in 2020 [1],
and I've confirmed I need it in U-Boot to enable gadget mode.

[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/patch/drivers/usb/dwc3?id=5b738211fb59e114727381d07c647a77c0010996

Signed-off-by: Thinh Nguyen <thinhn@synopsys.com>
Signed-off-by: Chris Morgan <macromorgan@hotmail.com>
Reviewed-by: Mattijs Korpershoek <mkorpershoek@kernel.org>
Link: https://lore.kernel.org/r/20260115230135.183158-4-macroalpha82@gmail.com
Signed-off-by: Mattijs Korpershoek <mkorpershoek@kernel.org>

diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
index d2ae892d5544d62d304d599fb1c89a9133746d95..24ae0c232f63daa9026440b752576c52f7a51a36 100644 (file)
--- a/drivers/usb/dwc3/gadget.c
+++ b/drivers/usb/dwc3/gadget.c
@@ -62,7 +62,7 @@ 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;
 }
@@ -1422,7 +1422,7 @@ 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 {
                udelay(2000);
@@ -2137,10 +2137,8 @@ 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);
        dwc->start_config_issued = false;
@@ -2189,7 +2187,7 @@ 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_stop_active_transfers(dwc);
@@ -2305,11 +2303,11 @@ static void dwc3_gadget_conndone_interrupt(struct dwc3 *dwc)
                if (dwc->has_lpm_erratum && dwc->revision >= DWC3_REVISION_240A)
                        reg |= DWC3_DCTL_LPM_ERRATA(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];
@@ -2417,7 +2415,7 @@ 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 f28a9755dcb3eda98a0e1b2662b2a368185aded6..e4f5a096956b40c24369004cd8a4eb3e8e294c98 100644 (file)
--- a/drivers/usb/dwc3/gadget.h
+++ b/drivers/usb/dwc3/gadget.h
@@ -104,4 +104,18 @@ static inline u32 dwc3_gadget_ep_get_transfer_index(struct dwc3 *dwc, u8 number)
        return 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 */