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 56686C43334 for ; Thu, 23 Jun 2022 17:49:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235184AbiFWRtl (ORCPT ); Thu, 23 Jun 2022 13:49:41 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34586 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235343AbiFWRry (ORCPT ); Thu, 23 Jun 2022 13:47:54 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5C6A4A17F3; Thu, 23 Jun 2022 10:11:17 -0700 (PDT) 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 1B7AB61D02; Thu, 23 Jun 2022 17:11:17 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id A4430C341C5; Thu, 23 Jun 2022 17:11:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1656004276; bh=QD0OPxsFQe0FpkE6nhAGjjP0t6YGreVfe/kZz0lqsXE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=xX2tz1lVF37KBUYYYEHza2buJPArdXGj4VKjfERlTgljhxqoZtqpSJjZf5jTcbOiy gTibivJ32cLTLnQz6eQYAsjvTuQtLx0yF3pEoCW8Zo1MX0SAND98WVE1GfDDnhRIiL uqbzW3CeprApI5awwzfNYv9a+3B5Ewg0dLWVXYFk= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, stable , =?UTF-8?q?Uwe=20Kleine-K=C3=B6nig?= , =?UTF-8?q?Uwe=20Kleine-K=C3=B6nig?= , =?UTF-8?q?Ilpo=20J=C3=A4rvinen?= Subject: [PATCH 4.14 222/237] serial: 8250: Store to lsr_save_flags after lsr read Date: Thu, 23 Jun 2022 18:44:16 +0200 Message-Id: <20220623164349.536818770@linuxfoundation.org> X-Mailer: git-send-email 2.36.1 In-Reply-To: <20220623164343.132308638@linuxfoundation.org> References: <20220623164343.132308638@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: Ilpo Järvinen commit be03b0651ffd8bab69dfd574c6818b446c0753ce upstream. Not all LSR register flags are preserved across reads. Therefore, LSR readers must store the non-preserved bits into lsr_save_flags. This fix was initially mixed into feature commit f6f586102add ("serial: 8250: Handle UART without interrupt on TEMT using em485"). However, that feature change had a flaw and it was reverted to make room for simpler approach providing the same feature. The embedded fix got reverted with the feature change. Re-add the lsr_save_flags fix and properly mark it's a fix. Link: https://lore.kernel.org/all/1d6c31d-d194-9e6a-ddf9-5f29af829f3@linux.intel.com/T/#m1737eef986bd20cf19593e344cebd7b0244945fc Fixes: e490c9144cfa ("tty: Add software emulated RS485 support for 8250") Cc: stable Acked-by: Uwe Kleine-König Signed-off-by: Uwe Kleine-König Signed-off-by: Ilpo Järvinen Link: https://lore.kernel.org/r/f4d774be-1437-a550-8334-19d8722ab98c@linux.intel.com Signed-off-by: Greg Kroah-Hartman --- drivers/tty/serial/8250/8250_port.c | 2 ++ 1 file changed, 2 insertions(+) --- a/drivers/tty/serial/8250/8250_port.c +++ b/drivers/tty/serial/8250/8250_port.c @@ -1524,6 +1524,8 @@ static inline void __stop_tx(struct uart if (em485) { unsigned char lsr = serial_in(p, UART_LSR); + p->lsr_saved_flags |= lsr & LSR_SAVE_FLAGS; + /* * To provide required timeing and allow FIFO transfer, * __stop_tx_rs485() must be called only when both FIFO and