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 09BD8C87FDD for ; Fri, 3 Mar 2023 21:51:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232695AbjCCVv0 (ORCPT ); Fri, 3 Mar 2023 16:51:26 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37686 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232069AbjCCVt3 (ORCPT ); Fri, 3 Mar 2023 16:49:29 -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 030EE6B5F3; Fri, 3 Mar 2023 13:45:56 -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 C228A61921; Fri, 3 Mar 2023 21:45:56 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id D0A04C433A4; Fri, 3 Mar 2023 21:45:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1677879956; bh=eyJN3ADA5oVBDcdDcIqcEf1aKewszDedfjIJZaz3EJA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=hOjd0OP4IoAXWEhgqDMeot5w40FH/lEBarUGDBxa+2Ad7JsPmytpIiE7Csvpwk0aE geuAxKIY/6AsbRITasw1Ay4wrpHEJLZd2xe/yj04hhS7bEKhb6FnMx4vQZWy0enAxb H0F2rfJvF3iVMLzNGBjUqlKsi/3FqvFQiJF2fEp0GuMbfFBOEr1LNhdVW77R5Tdq3Q OBQqXf2A5URKVDiAmU2LeEDZWx5+043vJwSpngYaL4Dm+gInHg9df1i2Z7YTqbgxAz n44EdRJSbWSETyDr2sEaNAUnMkopYX1eKx+p7aTHRFv7AAvJBqVpqKOrlPwlyBPtbG vgIstLEQc2ycQ== 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 5.15 11/50] tty: serial: fsl_lpuart: disable the CTS when send break signal Date: Fri, 3 Mar 2023 16:44:52 -0500 Message-Id: <20230303214531.1450154-11-sashal@kernel.org> X-Mailer: git-send-email 2.39.2 In-Reply-To: <20230303214531.1450154-1-sashal@kernel.org> References: <20230303214531.1450154-1-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 fc311df9f1c9d..1497098e100bf 100644 --- a/drivers/tty/serial/fsl_lpuart.c +++ b/drivers/tty/serial/fsl_lpuart.c @@ -1484,12 +1484,32 @@ 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