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 663D3C04FDF for ; Tue, 1 Aug 2023 09:48:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233562AbjHAJsf (ORCPT ); Tue, 1 Aug 2023 05:48:35 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45220 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233833AbjHAJsS (ORCPT ); Tue, 1 Aug 2023 05:48:18 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D9EAF3582 for ; Tue, 1 Aug 2023 02:46:42 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 50D69614DF for ; Tue, 1 Aug 2023 09:46:42 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 630FFC433C7; Tue, 1 Aug 2023 09:46:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1690883201; bh=l6Pcvzb0AvMm9DsHofV8Ursvkib+BQffG9sT3tfszYQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=V3WTRPsAP6+KL7IQg7znDSWmxbSmrIgQt7ZDSJAkf1W4ZDB034sYcmzwn7u78fyt8 h62H83aaQSlwSnm6EjsEuUcE+8QpS8GynQHAISfnqrdB3nItkvix+zcgdfkt+o+qAx kV/JlSEnCaGhrucQExNd6Gn4Rn7Zaf+wNbWJ2jnA= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, stable , Ruihong Luo , =?UTF-8?q?Ilpo=20J=C3=A4rvinen?= , Andy Shevchenko Subject: [PATCH 6.4 151/239] serial: 8250_dw: Preserve original value of DLF register Date: Tue, 1 Aug 2023 11:20:15 +0200 Message-ID: <20230801091931.102302108@linuxfoundation.org> X-Mailer: git-send-email 2.41.0 In-Reply-To: <20230801091925.659598007@linuxfoundation.org> References: <20230801091925.659598007@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: Ruihong Luo commit 748c5ea8b8796ae8ee80b8d3a3d940570b588d59 upstream. Preserve the original value of the Divisor Latch Fraction (DLF) register. When the DLF register is modified without preservation, it can disrupt the baudrate settings established by firmware or bootloader, leading to data corruption and the generation of unreadable or distorted characters. Fixes: 701c5e73b296 ("serial: 8250_dw: add fractional divisor support") Cc: stable Signed-off-by: Ruihong Luo Link: https://lore.kernel.org/stable/20230713004235.35904-1-colorsu1922%40gmail.com Reviewed-by: Ilpo Järvinen Reviewed-by: Andy Shevchenko Link: https://lore.kernel.org/r/20230713004235.35904-1-colorsu1922@gmail.com Signed-off-by: Greg Kroah-Hartman --- drivers/tty/serial/8250/8250_dwlib.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) --- a/drivers/tty/serial/8250/8250_dwlib.c +++ b/drivers/tty/serial/8250/8250_dwlib.c @@ -244,7 +244,7 @@ void dw8250_setup_port(struct uart_port struct dw8250_port_data *pd = p->private_data; struct dw8250_data *data = to_dw8250_data(pd); struct uart_8250_port *up = up_to_u8250p(p); - u32 reg; + u32 reg, old_dlf; pd->hw_rs485_support = dw8250_detect_rs485_hw(p); if (pd->hw_rs485_support) { @@ -270,9 +270,11 @@ void dw8250_setup_port(struct uart_port dev_dbg(p->dev, "Designware UART version %c.%c%c\n", (reg >> 24) & 0xff, (reg >> 16) & 0xff, (reg >> 8) & 0xff); + /* Preserve value written by firmware or bootloader */ + old_dlf = dw8250_readl_ext(p, DW_UART_DLF); dw8250_writel_ext(p, DW_UART_DLF, ~0U); reg = dw8250_readl_ext(p, DW_UART_DLF); - dw8250_writel_ext(p, DW_UART_DLF, 0); + dw8250_writel_ext(p, DW_UART_DLF, old_dlf); if (reg) { pd->dlf_size = fls(reg);