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 fdbb9d73aa8e496c180241975181d6f3021c68a5..13a2f5276072adfa05ec79608ad689432ee3ee10 100644 (file)
--- a/drivers/usb/gadget/udc/tegra-xudc.c
+++ b/drivers/usb/gadget/udc/tegra-xudc.c
@@ -1737,6 +1737,10 @@ 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);