usb: gadget: tegra-xudc: ACK ST_RC after clearing CTRL_RUN

commit 59820fde001500c167342257650541280c622b73 upstream.

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 <stable@kernel.org>
Signed-off-by: Wayne Chang <waynec@nvidia.com>
Link: https://lore.kernel.org/r/20250418081228.1194779-1-waynec@nvidia.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/usb/gadget/udc/tegra-xudc.c b/drivers/usb/gadget/udc/tegra-xudc.c
index fd7a9535973ed1a13c104c3dd346df970b02c073..771466cdf38590fb5d2c349cbe444cbcce46fb42 100644 (file)
--- a/drivers/usb/gadget/udc/tegra-xudc.c
+++ b/drivers/usb/gadget/udc/tegra-xudc.c
@@ -1743,6 +1743,10 @@ 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);