linux-kernel - [PATCH 1/1] usb: gadget: tegra-xudc: ACK ST_RC after clearing CTRL

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Message-ID: <20250418081228.1194779-1-waynec@nvidia.com>
Date: Fri, 18 Apr 2025 16:12:28 +0800
From: Wayne Chang <waynec@...dia.com>
To: <waynec@...dia.com>, <gregkh@...uxfoundation.org>,
	<thierry.reding@...il.com>, <jonathanh@...dia.com>
CC: <linux-usb@...r.kernel.org>, <linux-tegra@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <stable@...r.kernel.org>
Subject: [PATCH 1/1] usb: gadget: tegra-xudc: ACK ST_RC after clearing CTRL_RUN

We identified a bug where the ST_RC bit in the status register was not
being acknowledged after clearing the CTRL_RUN bit in the control
register. This could lead to unexpected behavior in the USB gadget
drivers.

This patch resolves the issue by adding the necessary code to explicitly
acknowledge ST_RC after clearing CTRL_RUN based on the programming
sequence, ensuring proper state transition.

Fixes: 49db427232fe ("usb: gadget: Add UDC driver for tegra XUSB device mode controller")
Cc: stable@...r.kernel.org
Signed-off-by: Wayne Chang <waynec@...dia.com>
---
 drivers/usb/gadget/udc/tegra-xudc.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/usb/gadget/udc/tegra-xudc.c b/drivers/usb/gadget/udc/tegra-xudc.c
index c7fdbc55fb0b..2957316fd3d0 100644
--- a/drivers/usb/gadget/udc/tegra-xudc.c
+++ b/drivers/usb/gadget/udc/tegra-xudc.c
@@ -1749,6 +1749,10 @@ static int __tegra_xudc_ep_disable(struct tegra_xudc_ep *ep)
 		val = xudc_readl(xudc, CTRL);
 		val &= ~CTRL_RUN;
 		xudc_writel(xudc, val, CTRL);
+
+		val = xudc_readl(xudc, ST);
+		if (val & ST_RC)
+			xudc_writel(xudc, ST_RC, ST);
 	}
 
 	dev_info(xudc->dev, "ep %u disabled\n", ep->index);
-- 
2.25.1