[PATCH] usb: dwc3: Soft reset phy on probe for host

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

When there's phy initialization, we need to initiate a soft-reset
sequence. That's done through USBCMD.HCRST in the xHCI driver and its
initialization, However, the dwc3 driver may modify core configs before
the soft-reset. This may result in some connection instability. So,
ensure the phy is ready before the controller updates the GCTL.PRTCAPDIR
or other settings by issuing phy soft-reset.

Note that some host-mode configurations may not expose device registers
to initiate the controller soft-reset (via DCTL.CoreSftRst). So we reset
through GUSB3PIPECTL and GUSB2PHYCFG instead.

Cc: stable@vger.kernel.org
Fixes: e835c0a4e23c ("usb: dwc3: don't reset device side if dwc3 was configured as host-only")
Reported-by: Kenta Sato <tosainu.maple@gmail.com>
Closes: https://lore.kernel.org/linux-usb/ZPUciRLUcjDywMVS@debian.me/
Signed-off-by: Thinh Nguyen <Thinh.Nguyen@synopsys.com>
---
 drivers/usb/dwc3/core.c | 39 ++++++++++++++++++++++++++++++++++++++-
 1 file changed, 38 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
index 9c6bf054f15d..343d2570189f 100644
--- a/drivers/usb/dwc3/core.c
+++ b/drivers/usb/dwc3/core.c
@@ -279,9 +279,46 @@ int dwc3_core_soft_reset(struct dwc3 *dwc)
 	 * XHCI driver will reset the host block. If dwc3 was configured for
 	 * host-only mode or current role is host, then we can return early.
 	 */
-	if (dwc->dr_mode == USB_DR_MODE_HOST || dwc->current_dr_role == DWC3_GCTL_PRTCAP_HOST)
+	if (dwc->current_dr_role == DWC3_GCTL_PRTCAP_HOST)
 		return 0;
 
+	/*
+	 * If the dr_mode is host and the dwc->current_dr_role is not the
+	 * corresponding DWC3_GCTL_PRTCAP_HOST, then the dwc3_core_init_mode
+	 * isn't executed yet. Ensure the phy is ready before the controller
+	 * updates the GCTL.PRTCAPDIR or other settings by soft-resetting
+	 * the phy.
+	 *
+	 * Note: GUSB3PIPECTL[n] and GUSB2PHYCFG[n] are port settings where n
+	 * is port index. If this is a multiport host, then we need to reset
+	 * all active ports.
+	 */
+	if (dwc->dr_mode == USB_DR_MODE_HOST) {
+		u32 usb3_port;
+		u32 usb2_port;
+
+		usb3_port = dwc3_readl(dwc->regs, DWC3_GUSB3PIPECTL(0));
+		usb3_port |= DWC3_GUSB3PIPECTL_PHYSOFTRST;
+		dwc3_writel(dwc->regs, DWC3_GUSB3PIPECTL(0), usb3_port);
+
+		usb2_port = dwc3_readl(dwc->regs, DWC3_GUSB2PHYCFG(0));
+		usb2_port |= DWC3_GUSB2PHYCFG_PHYSOFTRST;
+		dwc3_writel(dwc->regs, DWC3_GUSB2PHYCFG(0), usb2_port);
+
+		/* Small delay for phy reset assertion */
+		usleep_range(1000, 2000);
+
+		usb3_port &= ~DWC3_GUSB3PIPECTL_PHYSOFTRST;
+		dwc3_writel(dwc->regs, DWC3_GUSB3PIPECTL(0), usb3_port);
+
+		usb2_port &= ~DWC3_GUSB2PHYCFG_PHYSOFTRST;
+		dwc3_writel(dwc->regs, DWC3_GUSB2PHYCFG(0), usb2_port);
+
+		/* Wait for clock synchronization */
+		msleep(50);
+		return 0;
+	}
+
 	reg = dwc3_readl(dwc->regs, DWC3_DCTL);
 	reg |= DWC3_DCTL_CSFTRST;
 	reg &= ~DWC3_DCTL_RUN_STOP;

base-commit: 0bb80ecc33a8fb5a682236443c1e740d5c917d1d
-- 
2.38.1