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 D4AEBC64EC4 for ; Fri, 3 Mar 2023 21:56:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233158AbjCCV4U (ORCPT ); Fri, 3 Mar 2023 16:56:20 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46584 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233162AbjCCVyu (ORCPT ); Fri, 3 Mar 2023 16:54:50 -0500 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 744616A1D8; Fri, 3 Mar 2023 13:48:39 -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 dfw.source.kernel.org (Postfix) with ESMTPS id 905B261961; Fri, 3 Mar 2023 21:48:21 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9CD15C433EF; Fri, 3 Mar 2023 21:48:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1677880101; bh=2jaC8aJ077MjDoclgM23HMTM/z/zu78pjt+RJAb7sbs=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=EO4gLCU+qV8JX6SBVQHK2KgzMZusCu9jFbeGI5+tHt3ICLCxzjhQZO0sK/1Q6xoRc EU4WVpCuGaMmcOFa07IntDrvk6Q6eZWW9dG4zm+vwxottw2+8fGQAI4HZArYX64SSN bsVEv/51l7bwRLztm2WG4ncnMWoptA2zYy8xDs7Qt6i09Oxn38x31ZB7dZIUBNVq6T 3KMbGI/B/TvYIm783o702/6moUoVOyweyOUPzIa29reJlgp8jVCBUpRSKHs+8R044S ZClDYoT5NxhfEY8tfIj/zqeHjHl2P7sVC/PF/uTsUPVwH770t9BP+YqPLRpsSrUE+2 86Mc5j5ibXKfQ== 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 5.4 08/20] tty: serial: fsl_lpuart: disable the CTS when send break signal Date: Fri, 3 Mar 2023 16:47:54 -0500 Message-Id: <20230303214806.1453287-8-sashal@kernel.org> X-Mailer: git-send-email 2.39.2 In-Reply-To: <20230303214806.1453287-1-sashal@kernel.org> References: <20230303214806.1453287-1-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: linux-kernel@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 e84cef42f4b78..790e482625796 100644 --- a/drivers/tty/serial/fsl_lpuart.c +++ b/drivers/tty/serial/fsl_lpuart.c @@ -1370,12 +1370,32 @@ 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