On 2/4/26 1:12 PM, Siddharth Vadapalli wrote:
The cdns3_bind() function is responsible for identifying the appropriate
driver to bind to the USB Controller's device-tree node. If the device-tree
node has the 'dr_mode' property set to 'otg', the existing approach fails
to bind a driver, leading to loss of functionality.
To address this, use the VBUS Valid field of the OTG Status register to
determine the role as follows:
- If VBUS Valid field is set, it indicates that a USB Host is supplying
power and the Controller should assume the Peripheral role.
- If VBUS Valid field is clear, it indicates the absence of a USB Host and
the Controller should assume the Host role.
Additionally, when 'dr_mode' happens to be 'otg' and the STRAP settings
are not specified, use VBUS Valid to determine the role in cdns3_drd_init()
and assign it to cdns->dr_mode.
Signed-off-by: Siddharth Vadapalli <[email protected]>
---
Hello,
This patch is based on commit
a8d982e1f17 x86: cpu: Fix crash on FTRACE enabled builds
of the master branch of U-Boot.
Patch has been tested in the context of USB DFU boot on the J784S4 SoC
with a Cadence USB 3.0 Controller. Since the Linux device-tree for the
J784S4-EVM specifies the 'dr_mode' as OTG, due to reuse of Linux
device-tree by U-Boot, the 'dr_mode' of 'otg' causes USB DFU Boot to fail.
While one approach to fix it is to update 'dr_mode' to 'peripheral' in
the 'k3-j784s4-u-boot.dtsi' file as a HACK, it doesn't scale to other
SoCs and all of their 'u-boot.dtsi' files will have to be udpated as well.
While I am providing Texas Instruments SoCs as an example, I presume that
SoCs from other vendors are also affected by the 'dr_mode' being 'otg'.
This patch addresses the issue by using the VBUS Valid bit of the OTG
status register to override 'dr_mode' from 'otg' to a deterministic role
to enable functionality.
The USB DFU Boot Logs for the R5 SPL stage on J784S4 SoC with the current
U-Boot master as of commit
a8d982e1f17 x86: cpu: Fix crash on FTRACE enabled builds
are:
https://gist.github.com/Siddharth-Vadapalli-at-TI/b910f326b6c9fad760190bd299ae3ff3
and the logs indicate that USB DFU Boot fails. The failure is specifically
due to 'dr_mode' being 'otg' and the cdns3_bind() function failing to bind
the device-tree node to the peripheral driver required for DFU Boot.
The USB DFU Boot Logs for the R5 SPL stage with just this patch applied
while leaving 'dr_mode' at its existing value of 'otg' are:
https://gist.github.com/Siddharth-Vadapalli-at-TI/033b9772b6ab105b96806adf890848fe
Regards,
Siddharth.
drivers/usb/cdns3/core.c | 53 ++++++++++++++++++++++++++++++++++++++++
drivers/usb/cdns3/drd.c | 11 +++++++++
2 files changed, 64 insertions(+)
diff --git a/drivers/usb/cdns3/core.c b/drivers/usb/cdns3/core.c
index 4434dc15bec..b7be5c48fc9 100644
--- a/drivers/usb/cdns3/core.c
+++ b/drivers/usb/cdns3/core.c
@@ -392,6 +392,55 @@ static const struct udevice_id cdns3_ids[] = {
{ },
};
+/*
+ * The VBUS Valid Bit in the OTG Status register can be used to determine
+ * the role. When VBUS Valid is set, it indicates that a USB Host is supplying
+ * power, so the Controller should assume the PERIPHERAL role. If it isn't set,
+ * it indicates the absence of a USB Host, so the Controller should assume the
+ * HOST role. If the OTG Status register is inaccessible, return OTG role.
+ */
+static enum usb_dr_mode cdns3_get_otg_mode(ofnode node)
+{
+ struct cdns3 cdns, *cdnsp;
+ void __iomem *otg_regs;
+ fdt_addr_t otg_addr;
+ int otg_reg_index;
+ int vbus;
+
+ otg_reg_index = ofnode_stringlist_search(node, "reg-names", "otg");
+ if (otg_reg_index < 0)
+ return USB_DR_MODE_OTG;
This is wrong, the function should return error and possibly mode via
function parameter , do not conflate return value and mode please .
