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 15C0AC4167D for ; Mon, 7 Mar 2022 10:21:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240899AbiCGKTd (ORCPT ); Mon, 7 Mar 2022 05:19:33 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40462 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240524AbiCGKBF (ORCPT ); Mon, 7 Mar 2022 05:01:05 -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 381521ADBE; Mon, 7 Mar 2022 01:50:03 -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 CB91D60010; Mon, 7 Mar 2022 09:50:02 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id CDC18C340F3; Mon, 7 Mar 2022 09:50:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1646646602; bh=28iw5wanEUAnHfqZ+jvoczZh8C45puLtYOCOE0FUdeY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=lJmrUmCN2ASloqZHSnOwuTGqZ8h6CfR11ARjSIKU1h7xro++d8L65mfRPtx1Q1+9t DWeibhbwk3IDVLfnYhwOFT6D3A/Brl05QPwMog3qHlfzzDjKkgAadCsV85XV8D/sme UwOB6BcLVmj+llVvr0WoxjgXjzVGBXAYITGXnrAk= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Valentin Caron , Sasha Levin Subject: [PATCH 5.16 034/186] serial: stm32: prevent TDR register overwrite when sending x_char Date: Mon, 7 Mar 2022 10:17:52 +0100 Message-Id: <20220307091655.049293702@linuxfoundation.org> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20220307091654.092878898@linuxfoundation.org> References: <20220307091654.092878898@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Valentin Caron [ Upstream commit d3d079bde07e1b7deaeb57506dc0b86010121d17 ] When sending x_char in stm32_usart_transmit_chars(), driver can overwrite the value of TDR register by the value of x_char. If this happens, the previous value that was present in TDR register will not be sent through uart. This code checks if the previous value in TDR register is sent before writing the x_char value into register. Fixes: 48a6092fb41f ("serial: stm32-usart: Add STM32 USART Driver") Cc: stable Signed-off-by: Valentin Caron Link: https://lore.kernel.org/r/20220111164441.6178-2-valentin.caron@foss.st.com Signed-off-by: Greg Kroah-Hartman Signed-off-by: Sasha Levin --- drivers/tty/serial/stm32-usart.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/drivers/tty/serial/stm32-usart.c b/drivers/tty/serial/stm32-usart.c index 2d3fbcbfaf108..93c2a5c956540 100644 --- a/drivers/tty/serial/stm32-usart.c +++ b/drivers/tty/serial/stm32-usart.c @@ -520,10 +520,22 @@ static void stm32_usart_transmit_chars(struct uart_port *port) struct stm32_port *stm32_port = to_stm32_port(port); const struct stm32_usart_offsets *ofs = &stm32_port->info->ofs; struct circ_buf *xmit = &port->state->xmit; + u32 isr; + int ret; if (port->x_char) { if (stm32_port->tx_dma_busy) stm32_usart_clr_bits(port, ofs->cr3, USART_CR3_DMAT); + + /* Check that TDR is empty before filling FIFO */ + ret = + readl_relaxed_poll_timeout_atomic(port->membase + ofs->isr, + isr, + (isr & USART_SR_TXE), + 10, 1000); + if (ret) + dev_warn(port->dev, "1 character may be erased\n"); + writel_relaxed(port->x_char, port->membase + ofs->tdr); port->x_char = 0; port->icount.tx++; -- 2.34.1