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 04C45C6FD1F for ; Fri, 10 Mar 2023 14:43:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232830AbjCJOnN (ORCPT ); Fri, 10 Mar 2023 09:43:13 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:32932 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232889AbjCJOm6 (ORCPT ); Fri, 10 Mar 2023 09:42:58 -0500 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 16767121176 for ; Fri, 10 Mar 2023 06:42:50 -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 A1C2661962 for ; Fri, 10 Mar 2023 14:42:49 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id B386EC433D2; Fri, 10 Mar 2023 14:42:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1678459369; bh=2jaC8aJ077MjDoclgM23HMTM/z/zu78pjt+RJAb7sbs=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=SqcznyXv0vXXIO+13kbRwEz/oM1wDKGGjf8tVCPCGxusar3y95/mwpa+RJFKJrpC7 mwFbt9S+5LEA1AzkoFF0xvzLCuiiq94dRDqxyn0suJZTSigSDFR4jkiWTaBUeqHUMI sf7y0qNn16U8jXIKaVZ0G1iP65/NDb/oj6e+F6XI= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Sherry Sun , Sasha Levin Subject: [PATCH 5.4 338/357] tty: serial: fsl_lpuart: disable the CTS when send break signal Date: Fri, 10 Mar 2023 14:40:27 +0100 Message-Id: <20230310133749.573686643@linuxfoundation.org> X-Mailer: git-send-email 2.39.2 In-Reply-To: <20230310133733.973883071@linuxfoundation.org> References: <20230310133733.973883071@linuxfoundation.org> User-Agent: quilt/0.67 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 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 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