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([37.142.145.227]) by smtp.googlemail.com with ESMTPSA id ffacd0b85a97d-48e71b959c1sm5457300f8f.45.2026.10.30.15.37.10 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 30 Oct 2026 15:37:12 -0700 (PDT) From: Michael Zaidman To: Jiri Kosina , Benjamin Tissoires Cc: Linus Walleij , Bartosz Golaszewski , Greg Kroah-Hartman , Jiri Slaby , Raman Varabets , Germain Hebert , Christina Quast , Rio Liu , Bruno Giacomazzi , linux-input@vger.kernel.org, linux-serial@vger.kernel.org, linux-gpio@vger.kernel.org, linux-i2c@vger.kernel.org, linux-kernel@vger.kernel.org, Michael Zaidman Subject: [PATCH v2 07/15] HID: ft260: uart: enable flow control Date: Sat, 31 Oct 2026 00:36:29 +0200 Message-ID: <20261030223637.86907-8-michael.zaidman@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20261030223637.86907-1-michael.zaidman@gmail.com> References: <20261030223637.86907-1-michael.zaidman@gmail.com> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit The FT260 is a full-speed USB device. Interrupt transfers poll at 1 ms with a 64-byte max packet size, so the theoretical UART payload ceiling is about 60 kB/s (~600 kbaud in 8N1). The chip advertises baud rates above 1M and small transfers can work there, but large transfers are not reliable above 460800 baud without flow control. Stop forcing FT260_UART_CFG_FLOW_CTRL_NONE after termios setup. Honor CRTSCTS (RTS/CTS) and IXON/IXOFF (XON/XOFF) when configuring the UART. Tested at 1500000 baud both directions against an FT2232H with XON/XOFF and with RTS/CTS (~2.9 MB transfers, no data corruption). Signed-off-by: Michael Zaidman --- drivers/hid/hid-ft260.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) diff --git a/drivers/hid/hid-ft260.c b/drivers/hid/hid-ft260.c index 6f8d72938702..4b0b55c98f90 100644 --- a/drivers/hid/hid-ft260.c +++ b/drivers/hid/hid-ft260.c @@ -1897,8 +1897,12 @@ static int ft260_uart_change_speed(struct ft260_device *port, if (termios->c_cflag & CRTSCTS) req.flow_ctrl = FT260_UART_CFG_FLOW_CTRL_RTS_CTS; + else if (termios->c_iflag & (IXON | IXOFF)) + req.flow_ctrl = FT260_UART_CFG_FLOW_CTRL_XON_XOFF; else - req.flow_ctrl = FT260_UART_CFG_FLOW_CTRL_OFF; + req.flow_ctrl = FT260_UART_CFG_FLOW_CTRL_NONE; + + req.breaking = FT260_UART_CFG_BREAKING_NO; ft260_dbg("configured termios: flow control: %d, baudrate: %d, ", req.flow_ctrl, baud); @@ -1906,9 +1910,6 @@ static int ft260_uart_change_speed(struct ft260_device *port, req.data_bit, req.parity, req.stop_bit, req.breaking); - req.flow_ctrl = FT260_UART_CFG_FLOW_CTRL_NONE; - req.breaking = FT260_UART_CFG_BREAKING_NO; - mutex_lock(&port->lock); ret = ft260_hid_feature_report_set(hdev, (u8 *)&req, sizeof(req)); -- 2.43.0