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 1C1CEC433EF for ; Tue, 18 Jan 2022 03:38:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1353437AbiARDit (ORCPT ); Mon, 17 Jan 2022 22:38:49 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45276 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1351864AbiARDeS (ORCPT ); Mon, 17 Jan 2022 22:34:18 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C11E7C037029; Mon, 17 Jan 2022 19:09:34 -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 86127B811C4; Tue, 18 Jan 2022 03:09:33 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5FA5BC36AEF; Tue, 18 Jan 2022 03:09:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1642475372; bh=mOa3viRnCiyugN9lsjwtjitWUVuvU+gNzpDpjLjWNzE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=PGnKZIIFDJwwqsU80Zp6EhSzqeKxoOOh5mWmWM4/ekTaOiaO9UR/bx7At8NE+5U1n HHpTApGyM2tsuRC6u4BZp155eip8Da1PX4Z+iFGziYLWSeUluoXH2o82Kog2FRRDJj bPwzhpdzSFL5v8eKFA2LuwQhabA1y5gFRPHhiBXTOJnZpjc95cpZMOkYhgYzUVh7WP KlzijziV+yln+QL1IRjKn0CRXyrl/tMf/Mtb7zAlWJI9DtE/tnc7yZoTv9pxUEnsDN 3OfrU/kic2nXeREYAgTVU87yv2LlfkWEOcu/kbfLtvcfQq4d9iIHOCORFPqsPczIef ClpucDrtbDJwA== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Lukas Wunner , Russell King , Greg Kroah-Hartman , Sasha Levin , linux@armlinux.org.uk, jirislaby@kernel.org, linux-serial@vger.kernel.org Subject: [PATCH AUTOSEL 4.4 27/29] serial: pl010: Drop CR register reset on set_termios Date: Mon, 17 Jan 2022 22:08:20 -0500 Message-Id: <20220118030822.1955469-27-sashal@kernel.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20220118030822.1955469-1-sashal@kernel.org> References: <20220118030822.1955469-1-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: Lukas Wunner [ Upstream commit 08a0c6dff91c965e39905cf200d22db989203ccb ] pl010_set_termios() briefly resets the CR register to zero. Where does this register write come from? The PL010 driver's IRQ handler ambauart_int() originally modified the CR register without holding the port spinlock. ambauart_set_termios() also modified that register. To prevent concurrent read-modify-writes by the IRQ handler and to prevent transmission while changing baudrate, ambauart_set_termios() had to disable interrupts. That is achieved by writing zero to the CR register. However in 2004 the PL010 driver was amended to acquire the port spinlock in the IRQ handler, obviating the need to disable interrupts in ->set_termios(): https://git.kernel.org/history/history/c/157c0342e591 That rendered the CR register write obsolete. Drop it. Cc: Russell King Signed-off-by: Lukas Wunner Link: https://lore.kernel.org/r/fcaff16e5b1abb4cc3da5a2879ac13f278b99ed0.1641128728.git.lukas@wunner.de Signed-off-by: Greg Kroah-Hartman Signed-off-by: Sasha Levin --- drivers/tty/serial/amba-pl010.c | 3 --- 1 file changed, 3 deletions(-) diff --git a/drivers/tty/serial/amba-pl010.c b/drivers/tty/serial/amba-pl010.c index 5d41d5b92619a..7f4ba92739663 100644 --- a/drivers/tty/serial/amba-pl010.c +++ b/drivers/tty/serial/amba-pl010.c @@ -465,14 +465,11 @@ pl010_set_termios(struct uart_port *port, struct ktermios *termios, if ((termios->c_cflag & CREAD) == 0) uap->port.ignore_status_mask |= UART_DUMMY_RSR_RX; - /* first, disable everything */ old_cr = readb(uap->port.membase + UART010_CR) & ~UART010_CR_MSIE; if (UART_ENABLE_MS(port, termios->c_cflag)) old_cr |= UART010_CR_MSIE; - writel(0, uap->port.membase + UART010_CR); - /* Set baud rate */ quot -= 1; writel((quot & 0xf00) >> 8, uap->port.membase + UART010_LCRM); -- 2.34.1