From patchwork Thu Sep 5 22:43:06 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Lode Willems X-Patchwork-Id: 825865 Received: from mout-p-101.mailbox.org (mout-p-101.mailbox.org [80.241.56.151]) (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 4CEE41917D9 for ; Thu, 5 Sep 2024 22:43:50 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=80.241.56.151 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1725576232; cv=none; b=D7B05Vqgt5luYaQZxiFZKy0nKjgU2yIf/n2PZgjKAQ4EklM1ciMlhiQauAVrcrF6g2L2Qnba+xuTwCWth60WDCNKUlyEZeVaNAZS34dpd7j3AV34QaL3Dh9nFJg70xl/gfOkC8JBoBXRAzPRuCYoW8uaA4gUKndwxoa4Wv3pYUI= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1725576232; c=relaxed/simple; bh=A83N4EdPeH6klcG/vMdyruELpo5wAk/YKpG1Wz3MBI0=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=jhzD7CQtFMWfo5GXPcLV7S+FAYxylzuIyUpadgl4OLNaLwqqoDo2WDXOsWWCKX0PJCmDypaIUgSYzNgQN0eaNNlXrELO4YGZWWbOEzo/EpP1VQ1Q/qNK9/5iuVIKgCHqwlULoC81aKJePKb2w5V8QxmTRWEpHjjIcIkAHXKK1U8= 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=G7i6gfra; arc=none smtp.client-ip=80.241.56.151 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="G7i6gfra" Received: from smtp2.mailbox.org (smtp2.mailbox.org [IPv6:2001:67c:2050:b231:465::2]) (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-101.mailbox.org (Postfix) with ESMTPS id 4X0Dt41LWpz9sw4; Fri, 6 Sep 2024 00:43:40 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=lodewillems.com; s=MBO0001; t=1725576220; 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=/JLNue/8wbisDanCTsQEB4YImoEx4/W/N9DUeZBDSuo=; b=G7i6gfra9fShom2c8P1ygOGlH/NzgqgsX0OQ57RrnRIGdkE8l5YPPxlL/E7++mQIBedO4I l5kDDme18q4+UtCakwXLxU1l7IcbO4Gl3cdFXddKyC+J4zxZDYJqeswR4XBy9DojDxNvgf PftNl6YEBgS9k6bY+CdHVg0Z9c92Rp3oe/3SCNx+OaO2h5jBnhWNcC2fYisZPKUgF0HTqQ EBwJgs0HD/F2c35mhdrWxZrgV+UFKw88JX67cHK3YYQaCX/uoUwMsZSZuIFMCpn4FFTS9f L2f+cHz37gWT5EOxP/zJ3hqRBX1X/FDw1zHjBa9zNaB59CnELiL56LstVQIPag== From: Lode Willems To: Johan Hovold Cc: Lode Willems , linux-usb@vger.kernel.org Subject: [PATCH] USB: serial: CH341: add hardware flow control RTS/CTS Date: Fri, 6 Sep 2024 00:43:06 +0200 Message-ID: <20240905224326.7787-1-me@lodewillems.com> Precedence: bulk X-Mailing-List: linux-usb@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Rspamd-Queue-Id: 4X0Dt41LWpz9sw4 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 CC: linux-usb@vger.kernel.org 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 0870c6533f80..c3b3cae33a41 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); } /*