On 10-01-2020 16:46, Thierry Reding wrote:
On Fri, Dec 20, 2019 at 04:08:30PM +0800, JC Kuo wrote:
On 12/19/19 9:05 PM, Thierry Reding wrote:
On Wed, Dec 18, 2019 at 02:46:14PM +0530, Nagarjuna Kristam wrote:
Add usb-role-switch property for Tegra210 and Tegra186 platforms. This
entry is used by XUSB pad controller driver to register for role changes
for OTG/Peripheral capable USB 2 ports.
Signed-off-by: Nagarjuna Kristam<nkristam@xxxxxxxxxx>
---
V2:
- Moved usb-role-switch to seperate Required section as suggested by Thierry.
- Added reference to usb/usb-conn-gpio.txt for connector subnode.
---
.../devicetree/bindings/phy/nvidia,tegra124-xusb-padctl.txt | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/Documentation/devicetree/bindings/phy/nvidia,tegra124-xusb-padctl.txt b/Documentation/devicetree/bindings/phy/nvidia,tegra124-xusb-padctl.txt
index 9fb682e..23bf354 100644
--- a/Documentation/devicetree/bindings/phy/nvidia,tegra124-xusb-padctl.txt
+++ b/Documentation/devicetree/bindings/phy/nvidia,tegra124-xusb-padctl.txt
@@ -174,6 +174,12 @@ Required properties:
- "device": for USB device mode
- "otg": for USB OTG mode
+Required properties for OTG/Peripheral capable USB2 ports:
+- usb-role-switch: Boolean property to indicate that the port support OTG or
"supports", and also, why if it supports OTG*or* peripheral? Doesn't
OTG imply peripheral? OTG means it can be either peripheral or host,
right? So I think the end of that sentence can be just:
"... the port supports OTG."
An USB OTG port is capable of both USB host and peripheral operations. An USB
peripheral port can only act as an USB peripheral.
The micro USB ports found on Jetson TX1/TX2 platforms are micro-AB ports which
should implement both host and peripheral capabilities. We say such ports
support OTG. The micro USB port found on Jetson Nano is a micro-B port which
should implement peripheral capability only. We say such ports support
peripheral, rather than OTG.
I the port supports only peripheral mode, why do we need to have a
usb-role-switch property? Shouldn't we in that case have a mode property
with value "device"?
usb-mode-switch is only needed if mode = "otg", isn't it? In all other
cases the functionality is fixed (either host or peripheral) and the
mode cannot be switched.
Thierry
usb-role-switch is needed when mode == "otg" or "peripheral".
Device mode is detected via vbus GPIO irrespective of mode being
peripheral only or OTG.
Host mode is detected via id-gpio, in OTG case.
When mode is peripheral, role changes happens between USB_ROLE_DEVICE
and USB_ROLE_NONE, which are generally based on Vbus GPIO(hot plug)
detection.
When mode is otg, role changes happens between USB_ROLE_HOST,
USB_ROLE_DEVICE and USB_ROLE_NONE, which are detected via id-gpio,
vbus-gpio and no detection respectively.
-Nagarjuna
