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[78.88.45.245]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-b976cdb6936sm42936166b.37.2026.03.13.05.34.52 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 13 Mar 2026 05:34:54 -0700 (PDT) Message-ID: Date: Fri, 13 Mar 2026 13:34:51 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v1] arm64: dts: qcom: hamoa-iot-evk: support Bluetooth over both USB and UART To: Shuai Zhang , Bjorn Andersson , Konrad Dybcio , Rob Herring , Krzysztof Kozlowski , Conor Dooley Cc: linux-arm-msm@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-bluetooth@vger.kernel.org, cheng.jiang@oss.qualcomm.com, quic_chezhou@quicinc.com, wei.deng@oss.qualcomm.com, jinwang.li@oss.qualcomm.com, mengshi.wu@oss.qualcomm.com References: <20260311090921.1892191-1-shuai.zhang@oss.qualcomm.com> <97a3f3f2-e9e2-44ac-a682-0e0f0c100a45@oss.qualcomm.com> Content-Language: en-US From: Konrad Dybcio In-Reply-To: <97a3f3f2-e9e2-44ac-a682-0e0f0c100a45@oss.qualcomm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Proofpoint-ORIG-GUID: -3uwXm4q7a5vf8Eq9jN7mYNTfWvxSi7m X-Authority-Analysis: v=2.4 cv=FLwWBuos c=1 sm=1 tr=0 ts=69b40470 cx=c_pps a=7E5Bxpl4vBhpaufnMqZlrw==:117 a=FpWmc02/iXfjRdCD7H54yg==:17 a=IkcTkHD0fZMA:10 a=Yq5XynenixoA:10 a=s4-Qcg_JpJYA:10 a=VkNPw1HP01LnGYTKEx00:22 a=u7WPNUs3qKkmUXheDGA7:22 a=yOCtJkima9RkubShWh1s:22 a=o11hlXMYcrQWRnTjrNEA:9 a=3ZKOabzyN94A:10 a=QEXdDO2ut3YA:10 a=pJ04lnu7RYOZP9TFuWaZ:22 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwMzEzMDA5OSBTYWx0ZWRfXwUF+VVZ1wE9+ MKurw2NNRHb3v+8U00HnNH49S7mOL/AJQHFc5kqx/ZRKktG7mBVX1H/iPIRc7OuQ0fepMr3DiXw 2Rhccr/KD8tLFYZZERM/UsBJE+6kNTCj089oVN0+8qh/ESBzd43Ri6EPi022vOy1PP4BFZ6w51w SJEQY5NzjdmagtnYXk9sxTNtLZE5NeCIvFb0rmq6U9zBDbNyLA4JwGFs7rgXq8QxM02s3aG1FRF 9AtOPscJ9dN2oVb6z5m+canMiGF8Z5TzbpOvZgncYVdLXlhuR53I3Ayl2yBKEFVrCsrQAWPcsiU y57Xrdlh2Se0DAZc/yWwExWvxZ9dlpWSZWHCPGRY5vo9hVDEqOQEQXdpCV5ZyFrWsGRgV9JCcdL pDvi/vMEvNI7L/+CE5pGIPvKZoRvIhZXNNNtNI2qfjweP2h2euNyshLYvHDqzqLixcFP6/og4xr S/xVu242rosP4ld9zWA== X-Proofpoint-GUID: -3uwXm4q7a5vf8Eq9jN7mYNTfWvxSi7m X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.51,FMLib:17.12.100.49 definitions=2026-03-13_02,2026-03-13_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 impostorscore=0 bulkscore=0 malwarescore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 adultscore=0 phishscore=0 suspectscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2603050001 definitions=main-2603130099 On 3/13/26 7:37 AM, Shuai Zhang wrote: > Hi Konrad > > On 3/11/2026 9:07 PM, Konrad Dybcio wrote: >> On 3/11/26 10:09 AM, Shuai Zhang wrote: >>> When Bluetooth supports both USB and UART, the BT UART driver is >>> always loaded, while USB is hot-pluggable. As a result, when Bluetooth >>> is used over USB, the UART driver still be probed and drive BT_EN low, >>> which causes the Bluetooth device on USB to be disconnected. >> Is bluetooth connected over UART *and* USB simultaneously? > BT uses either UART or USB, never both at the same time. > > On platforms supporting both, the UART driver is always probed, while USB is hot‑pluggable. > > As a result, when BT runs over USB, the UART driver still probes and pulls BT_EN low, > > unintentionally powering off the USB BT device. Please describe in more detail how that difference can appear in practice. Is there an M.2 slot, into which different kinds of cards (i.e. ones with BT-over-USB vs BT-over-UART) may be plugged in? Konrad