On 01/03/26 06:50, Marek Vasut wrote:
On 3/1/26 2:02 AM, Siddharth Vadapalli wrote:
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()
.bind callback is meant to BIND the driver instance (to a DT node), it is
not meant to initialize the hardware. .probe callback is meant to
I agree. But that's exactly where the issue lies. When 'dr_mode' is set to
OTG, cdns3_bind() is unable to determine if the driver to bind to the DT
node is "cdns-usb3-host" or "cdns-usb3-peripheral".
Since [0], we attempt to identify if OTG should imply 'peripheral' or
'host'. But to do that, [0] needs to read the VBUS Valid field of the OTG
Status register. And register access requires the USB Controller to be
powered ON.
[0]: bfb530e06ca6 ("usb: cdns3: use VBUS Valid to determine role for
dr_mode OTG")
initialize the hardware. This is fundamental part of the U-Boot DM lazy
initialization scheme. If something does initialize hardware in .bind, then
it is very likely wrong.
, 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.
So, can we fix this so the HW initialization won't be happening in bind,
but instead in .probe ?
That isn't possible when 'dr_mode' is OTG because the .probe() callback
itself is determined by cdns3_bind(). Whether it is "cdns-usb3-host"
driver's .probe() callback or "cdns-usb3-peripheral" driver's .probe()
callback depends on cdns3_bind() being able to decide which driver to bind
to the DT node. And for cdns3_bind() to decide the driver when 'dr_mode' is
OTG, we need to read the VBUS Valid field. So cdns3_bind() needs to ensure
that the USB Controller is powered ON (device_probe() of parent).
