On 27/02/26 5:21 PM, Marek Vasut wrote:
On 2/27/26 6:59 AM, Siddharth Vadapalli wrote:
While commit bfb530e06ca6 ("usb: cdns3: use VBUS Valid to determine role
for dr_mode OTG") enhances the driver, it causes boot failure for non-USB
boot mode when the 'dr_mode' is 'otg'. The reason for it is that the
cdns3_get_otg_mode() function reads the USB Controller registers to
determine the appropriate role. If the boot mode happens to be USB, then
the USB Controller will be powered ON and the registers are accessible.
For non-USB boot modes, the USB Controller is not necessarily powered ON
as a result of which the register accesses cause boot failure.
Another issue is that the error code from cdns3_get_otg_mode() is
returned
as-is by cdns3_bind(). The cdns3_bind() function already has a comment
near the 'fail' label stating that an error code should __not__ be
returned
as it will cause the board to hang.
Fix the aforementioned issues in the following manner:
1. Probe the parent device before calling cdns3_get_otg_mode() to ensure
that the USB Controller is powered ON and its registers are
accessible.
2. If cdns3_get_otg_mode() returns an error code, instead of returning
the error code, jump to the 'fail' label and return '0'.
[...]
diff --git a/drivers/usb/cdns3/core.c b/drivers/usb/cdns3/core.c
index 10bc4cabed4..a775567b3bc 100644
--- a/drivers/usb/cdns3/core.c
+++ b/drivers/usb/cdns3/core.c
@@ -461,9 +461,18 @@ int cdns3_bind(struct udevice *parent)
/* Use VBUS Valid to determine role */
if (dr_mode == USB_DR_MODE_OTG) {
+ /*
+ * Since we perform register accesses in cdns3_get_otg_mode(),
+ * we need to ensure that the parent has been probed and that
+ * the USB Controller is powered ON.
+ */
+ ret = device_probe(parent);
+ if (ret)
+ goto fail;
+
ret = cdns3_get_otg_mode(parent, &dr_mode);
if (ret < 0)
- return ret;
+ goto fail;
}
Can you instead move this logic into driver .probe() ? Then you wouldn't
need the device_probe() hackage.
There are two users of cdns3_bind() which have registered their own
.bind() callback as cdns3_bind():
1. cdns3-starfive.c driver
2. cdns3-ti.c driver
Since .bind() is called before .probe(), and, since cdns3_bind() is also
the .bind() callback of the above drivers, device_probe() has to be
added here itself. Moreover, it is only due to the register accesses
being performed by the recently introduced cdns3_get_otg_mode() function
that we need the USB Controller to be powered ON at this stage.
Regards,
Siddharth.
