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 57726C3525C for ; Tue, 18 Jan 2022 03:06:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1354539AbiARDGi (ORCPT ); Mon, 17 Jan 2022 22:06:38 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37232 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1353138AbiARDBN (ORCPT ); Mon, 17 Jan 2022 22:01:13 -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 121B7C08E87B; Mon, 17 Jan 2022 18:46:55 -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 7280561311; Tue, 18 Jan 2022 02:46:54 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id DF65AC36B05; Tue, 18 Jan 2022 02:46:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1642474013; bh=ybTUdVpSs4tP9fA30UA8SByCPb6Bm5xSjfuBftAAKl0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=aw7JRu10KH61hsQwq8/KEKWhH21O3+Jf7NaMM0AnvgqR0VNPE8+SfkYwyzAy+QuaE GCXhH7AWejxTSd/sorgeOY/P0ZhlbTTk08y0LZ7fbN0MwRgOYFxp8oXHaizgsuN7IZ IQBitUZK2SDbDmyhKbNTIM2YKbnNYpY8T+jBH7oZJTCMsOsPp6xrnI7/MVRxCAdNP0 U5K6vbQLlPM2KiHlvY946AbaIoIZUNpHGgj8lmsyHlCKtQD0LjtIpJTKIDgQXrNN5z 2BgY+bxfBhiU77h6ejLOAUbsiPzfGK9F7TDgxJ94wRB4z1A2uPeQVBsXbTYJOWCqGM RslgDP+4U9S1Q== 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 5.4 70/73] serial: pl010: Drop CR register reset on set_termios Date: Mon, 17 Jan 2022 21:44:29 -0500 Message-Id: <20220118024432.1952028-70-sashal@kernel.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20220118024432.1952028-1-sashal@kernel.org> References: <20220118024432.1952028-1-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-serial@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 2c37d11726aba..13f882e5e7b76 100644 --- a/drivers/tty/serial/amba-pl010.c +++ b/drivers/tty/serial/amba-pl010.c @@ -452,14 +452,11 @@ 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