From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2FCD211C83 for ; Mon, 28 Aug 2023 10:37:40 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 78A71C433C7; Mon, 28 Aug 2023 10:37:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1693219060; bh=m+BUAl6LhaYkuAodSCfmpT10dKFia7ztCb6jxH32Yzk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=oLxH4qyTovvlbNhtEhlEGH/2kjZYpXk0se+lD6fMIYSgAGwWJNv7baws/X8LhwP0w l4ecSDTMhzjkowzEbQJ3R5JlYCAB+fuuoW/L5qct+bAdh1cgPD4B9sE3+5kOcgTyPB bwEO+488GSTi1HdJb1nCt6+n4pmMHHSRM4VRvb6c= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, stable , Sherry Sun Subject: [PATCH 5.4 058/158] tty: serial: fsl_lpuart: Clear the error flags by writing 1 for lpuart32 platforms Date: Mon, 28 Aug 2023 12:12:35 +0200 Message-ID: <20230828101159.264700233@linuxfoundation.org> X-Mailer: git-send-email 2.42.0 In-Reply-To: <20230828101157.322319621@linuxfoundation.org> References: <20230828101157.322319621@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 5.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Sherry Sun commit 282069845af388b08d622ad192b831dcd0549c62 upstream. Do not read the data register to clear the error flags for lpuart32 platforms, the additional read may cause the receive FIFO underflow since the DMA has already read the data register. Actually all lpuart32 platforms support write 1 to clear those error bits, let's use this method to better clear the error flags. Fixes: 42b68768e51b ("serial: fsl_lpuart: DMA support for 32-bit variant") Cc: stable Signed-off-by: Sherry Sun Link: https://lore.kernel.org/r/20230801022304.24251-1-sherry.sun@nxp.com Signed-off-by: Greg Kroah-Hartman --- drivers/tty/serial/fsl_lpuart.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) --- a/drivers/tty/serial/fsl_lpuart.c +++ b/drivers/tty/serial/fsl_lpuart.c @@ -1023,8 +1023,8 @@ static void lpuart_copy_rx_to_tty(struct unsigned long sr = lpuart32_read(&sport->port, UARTSTAT); if (sr & (UARTSTAT_PE | UARTSTAT_FE)) { - /* Read DR to clear the error flags */ - lpuart32_read(&sport->port, UARTDATA); + /* Clear the error flags */ + lpuart32_write(&sport->port, sr, UARTSTAT); if (sr & UARTSTAT_PE) sport->port.icount.parity++;