QCLINUX: arm64: dts: qcom: hamoa-iot-evk: support Bluetooth over both USB and UART#806
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… USB and UART On Hamoa boards, a single M.2 slot may host either a UART‑based or a USB‑based Bluetooth device, so the UART controller node is always present in DT while the USB path is hot‑pluggable. When Bluetooth operates over USB, the presence of the UART DT node still causes the hci_qca UART driver to probe, and during probe or power sequencing it may deassert BT_EN, cutting power to the shared Bluetooth device and disconnecting the USB interface. Model BT_EN as an always‑on fixed regulator so it cannot be toggled by the UART probe. This prevents the UART driver from interfering with Bluetooth operation when the device is connected over USB. Signed-off-by: Shuai Zhang <shuai.zhang@oss.qualcomm.com>
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On Hamoa boards, a single M.2 slot may host either a UART‑based or a USB‑based Bluetooth device, so the UART controller node is always present in DT while the USB path is hot‑pluggable. When Bluetooth operates over USB, the presence of the UART DT node still causes the hci_qca UART driver to probe, and during probe or power sequencing it may deassert BT_EN, cutting power to the shared Bluetooth device and disconnecting the USB interface.
Model BT_EN as an always‑on fixed regulator so it cannot be toggled by the UART probe. This prevents the UART driver from interfering with Bluetooth operation when the device is connected over USB.
Without this change, Bluetooth over USB does not work.
This is a temporary workaround. Once a proper M.2 binding or solution is upstreamed, both the DTS and driver changes will be reworked and re-submitted according to the M.2 model.
CRs-Fixed: 4464912