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Fri, 26 Jun 2020 04:24:20 +0000 From: Phu Luu To: "johan@kernel.org" , "gregkh@linuxfoundation.org" , "linux-usb@vger.kernel.org" , "linux-kernel@vger.kernel.org" CC: Brant Merryman , Richard Hendricks , =?windows-1258?q?Ph=FA_L?= =?windows-1258?q?=FDu_An?= , "hungnd3@fsoft.com.vn" Subject: [PATCH v3 2/2] USB: serial: cp210x: Proper RTS control when buffers fill Thread-Topic: [PATCH v3 2/2] USB: serial: cp210x: Proper RTS control when buffers fill Thread-Index: AQHWS3Gpakt8lWkQAEeJtxJ+vFX8Lg== Date: Fri, 26 Jun 2020 04:24:20 +0000 Message-ID: Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: authentication-results: kernel.org; dkim=none (message not signed) header.d=none;kernel.org; dmarc=none action=none header.from=silabs.com; x-originating-ip: [59.153.237.173] x-ms-publictraffictype: Email x-ms-office365-filtering-correlation-id: 03ca8aa3-63a4-4581-b8ae-08d81988cbfe x-ms-traffictypediagnostic: DM6PR11MB3290: x-ms-exchange-transport-forked: True x-microsoft-antispam-prvs: x-ms-oob-tlc-oobclassifiers: OLM:1186; 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This allows data to flow out, but new data will not come into the port. When re-opening the port, if auto-CTS is enabled on the cp210x, then auto-RTS must be re-enabled in the driver. Signed-off-by: Phu Luu Signed-off-by: Brant Merryman --- 06/09/2020: Patch v3 2/2 Modified based on feedback from Johan Hovold 12/18/2019: Patch v2 Broken into two patches and modified based on feedback from Johan Hovold 12/09/2019: Initial submission of patch "Proper RTS control when buffers fill" drivers/usb/serial/cp210x.c | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) diff --git a/drivers/usb/serial/cp210x.c b/drivers/usb/serial/cp210x.c index bcceb4ad8be0..091441b1c5b9 100644 --- a/drivers/usb/serial/cp210x.c +++ b/drivers/usb/serial/cp210x.c @@ -917,6 +917,7 @@ static void cp210x_get_termios_port(struct usb_serial_port *port, u32 baud; u16 bits; u32 ctl_hs; + u32 flow_repl; cp210x_read_u32_reg(port, CP210X_GET_BAUDRATE, &baud); @@ -1017,6 +1018,23 @@ static void cp210x_get_termios_port(struct usb_serial_port *port, ctl_hs = le32_to_cpu(flow_ctl.ulControlHandshake); if (ctl_hs & CP210X_SERIAL_CTS_HANDSHAKE) { dev_dbg(dev, "%s - flow control = CRTSCTS\n", __func__); + /* + * When the port is closed, the CP210x hardware disables + * auto-RTS and RTS is deasserted but it leaves auto-CTS when + * in hardware flow control mode. This prevents new data from + * being received by the port. When re-opening the port, if + * auto-CTS is enabled on the cp210x, then auto-RTS must be + * re-enabled in the driver. + */ + flow_repl = le32_to_cpu(flow_ctl.ulFlowReplace); + flow_repl &= ~CP210X_SERIAL_RTS_MASK; + flow_repl |= CP210X_SERIAL_RTS_SHIFT(CP210X_SERIAL_RTS_FLOW_CTL); + flow_ctl.ulFlowReplace = cpu_to_le32(flow_repl); + cp210x_write_reg_block(port, + CP210X_SET_FLOW, + &flow_ctl, + sizeof(flow_ctl)); + cflag |= CRTSCTS; } else { dev_dbg(dev, "%s - flow control = NONE\n", __func__);