usb: dwc3: gadget: fix writing NYET threshold

commit 01ea6bf5cb58b20cc1bd159f0cf74a76cf04bb69 upstream.

Before writing a new value to the register, the old value needs to be
masked out for the new value to be programmed as intended, because at
least in some cases the reset value of that field is 0xf (max value).

At the moment, the dwc3 core initialises the threshold to the maximum
value (0xf), with the option to override it via a DT. No upstream DTs
seem to override it, therefore this commit doesn't change behaviour for
any upstream platform. Nevertheless, the code should be fixed to have
the desired outcome.

Do so.

Fixes: 80caf7d21adc ("usb: dwc3: add lpm erratum support")
Cc: stable@vger.kernel.org # 5.10+ (needs adjustment for 5.4)
Signed-off-by: André Draszik <andre.draszik@linaro.org>
Acked-by: Thinh Nguyen <Thinh.Nguyen@synopsys.com>
Link: https://lore.kernel.org/r/20241209-dwc3-nyet-fix-v2-1-02755683345b@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/usb/dwc3/core.h b/drivers/usb/dwc3/core.h
index 3d434c110bdb6e6735c02e72cc8c97158fe804e1..d4a37a1539d2cf3e00b4455f321b57acf760aaa4 100644 (file)
--- a/drivers/usb/dwc3/core.h
+++ b/drivers/usb/dwc3/core.h
@@ -430,6 +430,7 @@
 #define DWC3_DCTL_TRGTULST_SS_INACT    (DWC3_DCTL_TRGTULST(6))
 
 /* These apply for core versions 1.94a and later */
+#define DWC3_DCTL_NYET_THRES_MASK      (0xf << 20)
 #define DWC3_DCTL_NYET_THRES(n)                (((n) & 0xf) << 20)
 
 #define DWC3_DCTL_KEEP_CONNECT         BIT(19)

diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
index 7ab6307fba85f0b01da1939b49611059830d5d75..d39906248850a8eb112914c696f0644cbbdac247 100644 (file)
--- a/drivers/usb/dwc3/gadget.c
+++ b/drivers/usb/dwc3/gadget.c
@@ -4004,8 +4004,10 @@ static void dwc3_gadget_conndone_interrupt(struct dwc3 *dwc)
                WARN_ONCE(DWC3_VER_IS_PRIOR(DWC3, 240A) && dwc->has_lpm_erratum,
                                "LPM Erratum not available on dwc3 revisions < 2.40a\n");
 
-               if (dwc->has_lpm_erratum && !DWC3_VER_IS_PRIOR(DWC3, 240A))
+               if (dwc->has_lpm_erratum && !DWC3_VER_IS_PRIOR(DWC3, 240A)) {
+                       reg &= ~DWC3_DCTL_NYET_THRES_MASK;
                        reg |= DWC3_DCTL_NYET_THRES(dwc->lpm_nyet_threshold);
+               }
 
                dwc3_gadget_dctl_write_safe(dwc, reg);
        } else {