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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-arm-msm@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-GUID: KNfsymvDFJadnP5Kw-nNvy4_5-D051Gn X-Authority-Analysis: v=2.4 cv=IIIPywvG 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=ZpdpYltYx_vBUK5n70dp:22 a=o11hlXMYcrQWRnTjrNEA:9 a=3ZKOabzyN94A:10 a=QEXdDO2ut3YA:10 a=pJ04lnu7RYOZP9TFuWaZ:22 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwMzEzMDA5OSBTYWx0ZWRfX1E+4rCXx9/ng unIHCkGEXSu01p3JvqIrQaJbhllCmUf+AVkKceuwSgfwDKCVjDwaoO28WdgC5INct8LxiejOXDt l7zXEO7DCnWYUMLoPwjk7jpbVkR2nVTkb0UZpOb7gi6thy2R0yYUJTLtVUB4sD5ecYF99ansZ8g VuIP08p/WfN51kMdssVpiCUoKx/p0yZI4Q49glyvSsBQAZHtNpL4PS68Wac0/fu5zAcHewLWX/p Ge4IU7ns2O0GQxQwADaCLYBEJZMGqnALxdxb+CZuGSKFqgpJaINcW35nuRbov5cP5tRTO9aOLbf c6HoL+7Utwp83FwMVHqT2dxtiqan5fht5K8rfN1dPchN7d1/VYYf/5Rc2GooJwIKQRnV/F2J/PV Oj9KSpQsT6ZtV5xTkCB3O8jBuM/NVYs1+BMJcuhmPmoVZFg91TPFMrPgHzcIf+G8NECwJ2LqYbR 3FEOnSO3UhTgJU+SYBA== X-Proofpoint-ORIG-GUID: KNfsymvDFJadnP5Kw-nNvy4_5-D051Gn 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 suspectscore=0 bulkscore=0 priorityscore=1501 phishscore=0 lowpriorityscore=0 clxscore=1015 adultscore=0 impostorscore=0 spamscore=0 malwarescore=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