From patchwork Wed Nov 13 18:08:27 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Lode Willems X-Patchwork-Id: 843070 Received: from mout-p-103.mailbox.org (mout-p-103.mailbox.org [80.241.56.161]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 777E82038D4; Wed, 13 Nov 2024 18:18:30 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=80.241.56.161 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1731521913; cv=none; b=AR8qNwdHpzl1TPOc5TPLGveFcKgkGBvd4gPujEBdxfZB/LcyFoWhIBcAwLtfoj/G5k1L2gaHwm3KsfhWv5CLg3o6pQ0/cW5ctds2JYQV5OZTIZ8t83G9eooNH7VfX35pTGebVO7ffDwvM6CQPjlWJlH/UaeCJz1FNXOAI4PiMk4= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1731521913; c=relaxed/simple; bh=rj2NLCwxfqX5S1Pk2cVGrE1lsmdAA+JKNUEah2kiwKc=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=FJR7IGxWNnMBKWr3L5Q+eDqyyav5tbjRv5yshX0ZT1AoU+TGX2yIPfBP2l6WXSpqPR0zAOJmPlPldxXENXOckY3aWuaBzuSwkaHJ97+4f1aknAnXdvmk58eG0kK4g9406Ab8kNHLlQKFDQuhU1I12GFcfQERMNc28QVkoUVBO2A= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=lodewillems.com; spf=pass smtp.mailfrom=lodewillems.com; dkim=pass (2048-bit key) header.d=lodewillems.com header.i=@lodewillems.com header.b=FiJmoXtu; arc=none smtp.client-ip=80.241.56.161 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=lodewillems.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=lodewillems.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=lodewillems.com header.i=@lodewillems.com header.b="FiJmoXtu" Received: from smtp102.mailbox.org (smtp102.mailbox.org [10.196.197.102]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by mout-p-103.mailbox.org (Postfix) with ESMTPS id 4XpWXh596yz9sdR; Wed, 13 Nov 2024 19:10:12 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=lodewillems.com; s=MBO0001; t=1731521412; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=N7znE+uJkFhUaDn+LNG3BIj1Ldrazv+bL1n4aDjRP/c=; b=FiJmoXtuUYaeJCgGdfTqrOj7V+059o6PknX+NT8A2Z+gUizdUfKsEHagn3z3vq1dJLYpch gAus0lAkzq4naj0C8MsA3XYZVPedxl4wb+jgYPilWoId0mO/iAhGia6ftLfMKac6ey/qr8 6baZ9MtbAuH6mQG0n/KGVr8kzh2ekuTCh+ZgRtGYcbyyWyQNjpWiAs+m/Davp6HSwJCvun 4UKumkvCWqYyDWL4QHyYuIfQGRlYpFhL0lAYsJI6F5IEgsi2wtoLU6JYLScmTVdaaZEktP LF78XYqm3MYIpbpKKwG9Ro3TYl9sXj9t+wRN7LHH42WUtg1Z6R4C4T40l73lhA== From: Lode Willems To: johan@kernel.org Cc: gregkh@linuxfoundation.org, linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, Lode Willems Subject: [PATCH RESEND] USB: serial: CH341: add hardware flow control RTS/CTS Date: Wed, 13 Nov 2024 19:08:27 +0100 Message-ID: <20241113180930.3741-1-me@lodewillems.com> Precedence: bulk X-Mailing-List: linux-usb@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 This adds support for enabling and disabling RTS/CTS hardware flow control. Tested using a CH340E in combination with a CP2102. Fixes part of the following bug report: Link: https://bugzilla.kernel.org/show_bug.cgi?id=197109 Signed-off-by: Lode Willems --- drivers/usb/serial/ch341.c | 41 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 41 insertions(+) diff --git a/drivers/usb/serial/ch341.c b/drivers/usb/serial/ch341.c index d10e4c4848a0..62237f657320 100644 --- a/drivers/usb/serial/ch341.c +++ b/drivers/usb/serial/ch341.c @@ -63,6 +63,7 @@ #define CH341_REG_DIVISOR 0x13 #define CH341_REG_LCR 0x18 #define CH341_REG_LCR2 0x25 +#define CH341_REG_FLOW_CTL 0x27 #define CH341_NBREAK_BITS 0x01 @@ -77,6 +78,9 @@ #define CH341_LCR_CS6 0x01 #define CH341_LCR_CS5 0x00 +#define CH341_FLOW_CTL_NONE 0x000 +#define CH341_FLOW_CTL_RTSCTS 0x101 + #define CH341_QUIRK_LIMITED_PRESCALER BIT(0) #define CH341_QUIRK_SIMULATE_BREAK BIT(1) @@ -478,6 +482,41 @@ static int ch341_open(struct tty_struct *tty, struct usb_serial_port *port) return r; } +static void ch341_set_flow_control(struct tty_struct *tty, + struct usb_serial_port *port, + const struct ktermios *old_termios) +{ + int r; + + if (old_termios && + C_CRTSCTS(tty) == (old_termios->c_cflag & CRTSCTS)) + return; + + if (C_CRTSCTS(tty)) { + r = ch341_control_out(port->serial->dev, CH341_REQ_WRITE_REG, + CH341_REG_FLOW_CTL | + ((u16)CH341_REG_FLOW_CTL << 8), + CH341_FLOW_CTL_RTSCTS); + if (r < 0) { + dev_err(&port->dev, + "%s - failed to enable flow control: %d\n", + __func__, r); + tty->termios.c_cflag &= ~CRTSCTS; + } + } else { + r = ch341_control_out(port->serial->dev, CH341_REQ_WRITE_REG, + CH341_REG_FLOW_CTL | + ((u16)CH341_REG_FLOW_CTL << 8), + CH341_FLOW_CTL_NONE); + if (r < 0) { + dev_err(&port->dev, + "%s - failed to disable flow control: %d\n", + __func__, r); + tty->termios.c_cflag |= CRTSCTS; + } + } +} + /* Old_termios contains the original termios settings and * tty->termios contains the new setting to be used. */ @@ -546,6 +585,8 @@ static void ch341_set_termios(struct tty_struct *tty, spin_unlock_irqrestore(&priv->lock, flags); ch341_set_handshake(port->serial->dev, priv->mcr); + + ch341_set_flow_control(tty, port, old_termios); } /*