On Sat, Sep 05, 2026 at 08:59:05PM +0530, Krishna Kurapati wrote:
eUSB2 (Embedded USB2) is a MIPI Alliance standard for chip-to-chip USB2
signaling. Unlike standard USB2, which uses 3.3V signaling, eUSB2 uses
low-voltage differential signaling (~0.4V) and requires a repeater to
interface with external USB2 ports. Because of these differences, eUSB2
PHY initialization sequences, voltage tuning, and register configuration
are distinct from USB2.
Additionally, eUSB2 targets handle wakeup interrupts differently
depending on device speed when operating in host mode. According to the
eUSB2 specification, remote wakeup signaling in host mode is detected
via different data-line assertions based on the connected device speed:
- Low-speed devices: the host repeater drives eD+ to logic '1' upon
detecting a K-state on the USB lines during remote wakeup (eUSB2
spec, Section 5.5.14).
- Full-speed/high-speed devices: the host repeater drives eD- to
logic '1' upon detecting a K-state during remote wakeup (eUSB2 spec,
Sections 5.5.15 and 5.5.18).
Since the eUSB2 PHY's DP and DM lines need to be configured differently
from USB2 PHYs, controllers should be able to query the PHY type and
configure wakeup interrupts accordingly.
Add PHY_TYPE_EUSB2 to distinguish eUSB2 PHYs from standard USB2 PHYs.
Acked-by: Krzysztof Kozlowski <redacted>
Signed-off-by: Krishna Kurapati <redacted>
Reviewed-by: Manivannan Sadhasivam <redacted>
- Mani
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