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 B15E8C4332F for ; Tue, 18 Jan 2022 03:17:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S245463AbiARDRt (ORCPT ); Mon, 17 Jan 2022 22:17:49 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39106 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1349269AbiARDG7 (ORCPT ); Mon, 17 Jan 2022 22:06:59 -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 8C3D3C014F34; Mon, 17 Jan 2022 18:49:03 -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 241E161336; Tue, 18 Jan 2022 02:49:03 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 90223C36AF4; Tue, 18 Jan 2022 02:49:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1642474142; bh=ybTUdVpSs4tP9fA30UA8SByCPb6Bm5xSjfuBftAAKl0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=CRBRXqP6gBr33YzF5xvfpL9kxaZ5IjdaPl5t0k3V2Lkcz+6flDT4xoJj/madINaFD CZ7HYIlVp05TWCYH4W+j44xW9wQjnyXX2qNYERozI5Ai38AsNqUgcLJQw141d7spl7 TMhDFzIvXoFuO/ptfThFCoWsl8IwfMPAKWQuX14QC9xKJF1YemDqz+R8zbhGJvUvOo B5lFV6vWYJmQdiEESCNFdxKq/aOy0Mdt88Zy73S1QEnG70XHBlLsdAAz6MAKGEvOD6 kxMrzd1eJ6TYkKPJpkMw5NFXeF+gfT2h6/Zzl1nI/hQYtHa3DQleCbCqEjsjutaTZB AF90kW4mVy4Dg== 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 4.19 57/59] serial: pl010: Drop CR register reset on set_termios Date: Mon, 17 Jan 2022 21:46:58 -0500 Message-Id: <20220118024701.1952911-57-sashal@kernel.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20220118024701.1952911-1-sashal@kernel.org> References: <20220118024701.1952911-1-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