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Thu, 15 Jan 2026 15:04:08 -0800 (PST) Received: from localhost.localdomain ([2600:1700:fb0:1bc0::54]) by smtp.gmail.com with ESMTPSA id 006d021491bc7-661187a0000sm394787eaf.14.2026.01.15.15.04.07 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 15 Jan 2026 15:04:07 -0800 (PST) From: Chris Morgan To: u-boot@lists.denx.de Cc: thinhn@synopsys.com, neil.armstrong@linaro.org, quic_varada@quicinc.com, felipe.balbi@linux.intel.com, mkorpershoek@kernel.org, lukma@denx.de, trini@konsulko.com, marex@denx.de, macromorgan@hotmail.com Subject: [PATCH V2 3/4] usb: dwc3: gadget: Don't send unintended link state change Date: Thu, 15 Jan 2026 17:01:34 -0600 Message-ID: <20260115230135.183158-4-macroalpha82@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260115230135.183158-1-macroalpha82@gmail.com> References: <20260115230135.183158-1-macroalpha82@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-BeenThere: u-boot@lists.denx.de X-Mailman-Version: 2.1.39 Precedence: list List-Id: U-Boot discussion List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: u-boot-bounces@lists.denx.de Sender: "U-Boot" X-Virus-Scanned: clamav-milter 0.103.8 at phobos.denx.de X-Virus-Status: Clean From: Chris Morgan 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 Signed-off-by: Chris Morgan --- 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 d2ae892d554..24ae0c232f6 100644 --- 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 f28a9755dcb..e4f5a096956 100644 --- 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 */ -- 2.43.0