From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 262E4C61DA3 for ; Fri, 3 Mar 2023 22:02:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233521AbjCCWCX (ORCPT ); Fri, 3 Mar 2023 17:02:23 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:32824 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232136AbjCCWA7 (ORCPT ); Fri, 3 Mar 2023 17:00:59 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8EAA264273; Fri, 3 Mar 2023 13:52:30 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 65B79B81A31; Fri, 3 Mar 2023 21:49:01 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 40875C4339C; Fri, 3 Mar 2023 21:49:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1677880141; bh=yE1Ac/ZY7CIZKEOnutqnUzKRE/nHXsgu8K43DWI48OM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=YKcuWICVzRT4scqr+ltL6JMnM4nHhou24tmN/x4XrHHnhFseBSBbsr+fEDVjPTD7n zzLgMH1ltuFIYgrd8hvA6Ivk+LJnN8NKZM73yp91DB90+pLMUlmcjudcjB8/kZKQjd sdIa1H/jq4bBLpdGFAUoa88niuU3vQ2/Mec5jn4upmImFEPMQnclMYgqknHwQpdztk wcOKyfDgH+pQAnQoyzvb9wmydoJWnhbX+9gCInN9UlTcYThCRhNfnsNNZmBb5OINl9 IbZHo22Mp6VpSqoYbCKIPNwZcu/Yr8Yd4vcLNnJS70HFBzc5jlpKpM7KlTJAZNrKBj 6pHKW7lZXrHhQ== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Sherry Sun , Greg Kroah-Hartman , Sasha Levin , jirislaby@kernel.org, linux-serial@vger.kernel.org Subject: [PATCH AUTOSEL 4.19 06/16] tty: serial: fsl_lpuart: disable the CTS when send break signal Date: Fri, 3 Mar 2023 16:48:39 -0500 Message-Id: <20230303214849.1454002-6-sashal@kernel.org> X-Mailer: git-send-email 2.39.2 In-Reply-To: <20230303214849.1454002-1-sashal@kernel.org> References: <20230303214849.1454002-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Sherry Sun [ Upstream commit c4c81db5cf8bc53d6160c3abf26d382c841aa434 ] LPUART IP has a bug that it treats the CTS as higher priority than the break signal, which cause the break signal sending through UARTCTRL_SBK may impacted by the CTS input if the HW flow control is enabled. Add this workaround patch to fix the IP bug, we can disable CTS before asserting SBK to avoid any interference from CTS, and re-enable it when break off. Such as for the bluetooth chip power save feature, host can let the BT chip get into sleep state by sending a UART break signal, and wake it up by turning off the UART break. If the BT chip enters the sleep mode successfully, it will pull up the CTS line, if the BT chip is woken up, it will pull down the CTS line. If without this workaround patch, the UART TX pin cannot send the break signal successfully as it affected by the BT CTS pin. After adding this patch, the BT power save feature can work well. Signed-off-by: Sherry Sun Link: https://lore.kernel.org/r/20221214031137.28815-2-sherry.sun@nxp.com Signed-off-by: Greg Kroah-Hartman Signed-off-by: Sasha Levin --- drivers/tty/serial/fsl_lpuart.c | 24 ++++++++++++++++++++++-- 1 file changed, 22 insertions(+), 2 deletions(-) diff --git a/drivers/tty/serial/fsl_lpuart.c b/drivers/tty/serial/fsl_lpuart.c index 069d02354c825..6ea1d23623e51 100644 --- a/drivers/tty/serial/fsl_lpuart.c +++ b/drivers/tty/serial/fsl_lpuart.c @@ -1195,12 +1195,32 @@ static void lpuart_break_ctl(struct uart_port *port, int break_state) static void lpuart32_break_ctl(struct uart_port *port, int break_state) { - unsigned long temp; + unsigned long temp, modem; + struct tty_struct *tty; + unsigned int cflag = 0; + + tty = tty_port_tty_get(&port->state->port); + if (tty) { + cflag = tty->termios.c_cflag; + tty_kref_put(tty); + } temp = lpuart32_read(port, UARTCTRL) & ~UARTCTRL_SBK; + modem = lpuart32_read(port, UARTMODIR); - if (break_state != 0) + if (break_state != 0) { temp |= UARTCTRL_SBK; + /* + * LPUART CTS has higher priority than SBK, need to disable CTS before + * asserting SBK to avoid any interference if flow control is enabled. + */ + if (cflag & CRTSCTS && modem & UARTMODIR_TXCTSE) + lpuart32_write(port, modem & ~UARTMODIR_TXCTSE, UARTMODIR); + } else { + /* Re-enable the CTS when break off. */ + if (cflag & CRTSCTS && !(modem & UARTMODIR_TXCTSE)) + lpuart32_write(port, modem | UARTMODIR_TXCTSE, UARTMODIR); + } lpuart32_write(port, temp, UARTCTRL); } -- 2.39.2