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[195.231.44.239]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-499b2b35386sm25640585e9.4.2026.08.20.02.17.36 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 20 Aug 2026 02:17:37 -0700 (PDT) Message-ID: <3f078f41-b971-424c-9258-b309a7d5d223@redhat.com> Date: Thu, 20 Aug 2026 11:17:35 +0200 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 net-next v5 0/3] net: wwan: support DTR/RTS on AT ports via MHI IP_CTRL To: Peter Hunt , loic.poulain@oss.qualcomm.com, mani@kernel.org, ryazanov.s.a@gmail.com Cc: johannes@sipsolutions.net, netdev@vger.kernel.org, mhi@lists.linux.dev, linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org References: <20260819224927.2274790-1-peter.hunt@opengear.com> From: Paolo Abeni Content-Language: en-US In-Reply-To: <20260819224927.2274790-1-peter.hunt@opengear.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 8/20/26 12:49 AM, Peter Hunt wrote: > Qualcomm/Sierra SDX55/SDX65 modems (e.g. EM9291) withhold unsolicited AT > result codes until the host asserts DTR. The in-tree mhi_wwan_ctrl driver > exposed AT ports but never signalled DTR, so URCs never reached userspace. > > Patch 1 extends the wwan core with an optional ->dtr_rts(port, mdmbits) port > op. The TIOCM bitmask state is tracked entirely in the wwan core; drivers > receive the full bitmask so they can drive DTR and RTS independently. The > core raises DTR/RTS on first open of any AT port whose driver implements > ->dtr_rts and drops them on last close, mirroring TTY semantics. In the > ioctl path mdmbits is re-read under data_lock inside ops_lock so the value > passed always reflects the committed state and concurrent ioctls are > correctly ordered. wwan_remove_port() also de-asserts on hot-unplug. > > Patch 2 enables the IP_CTRL MHI channel in the Sierra PCI table so that > the IP_CTRL driver (patch 3) is actually bound on those controllers. > > Patch 3 adds a second mhi_driver that binds the IP_CTRL channel and > registers a ->dtr_rts op so that the wwan core's open/close DTR raise/drop > and userspace TIOCMSET calls both reach the modem. A single recycled sink > buffer keeps the IP_CTRL DL ring live so the modem's transmit path does not > stall. The existing AT/QMI/MBIM data path is untouched. ## Form letter - net-next-closed We have already submitted our pull request with net-next material for v7.3, and therefore net-next is closed for new drivers, features, code refactoring and optimizations. We are currently accepting bug fixes only. Please repost when net-next reopens after Aug 31st. RFC patches sent for review only are obviously welcome at any time. See: https://www.kernel.org/doc/html/next/process/maintainer-netdev.html#development-cycle