From nobody Mon Sep 29 21:12:46 2025 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 76AC1C00140 for ; Tue, 16 Aug 2022 00:42:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S243971AbiHPAmS (ORCPT ); Mon, 15 Aug 2022 20:42:18 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49000 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S244919AbiHPAjo (ORCPT ); Mon, 15 Aug 2022 20:39:44 -0400 Received: from sin.source.kernel.org (sin.source.kernel.org [145.40.73.55]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E31CAD34F9; Mon, 15 Aug 2022 13:38:43 -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 sin.source.kernel.org (Postfix) with ESMTPS id C6898CE12C6; Mon, 15 Aug 2022 20:38:41 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 47EE5C433C1; Mon, 15 Aug 2022 20:38:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1660595920; bh=wiCUhAHDhxGJi4ufS9Hr7pAE+pr7JKbHhtWjygcB68g=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=MTyNcYHoAvXzX4Xb6P/G5omJcdat1toIjRbjvzAnEw6tR1k7NFzfBmxSP5g9tsoZH iBKuLkwhGrwtN5awWwifJ82p0OPESw73EuQlLlkjL5qh30Wp4DtvDgP+NsQicHoNH0 6YHmm2xQtSg3LVoiD/6+6Aq/sOs1b8vTlei0hCN0= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Andy Shevchenko , =?UTF-8?q?Ilpo=20J=C3=A4rvinen?= , Sasha Levin Subject: [PATCH 5.19 0899/1157] serial: 8250: Create serial_lsr_in() Date: Mon, 15 Aug 2022 20:04:15 +0200 Message-Id: <20220815180515.413383265@linuxfoundation.org> X-Mailer: git-send-email 2.37.2 In-Reply-To: <20220815180439.416659447@linuxfoundation.org> References: <20220815180439.416659447@linuxfoundation.org> User-Agent: quilt/0.67 MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Ilpo J=C3=A4rvinen [ Upstream commit bdb70c424df1543bc02ee2639aecebd20318c599 ] LSR register readers need to be careful in order to not lose bits that are not preserved across reads. Create a helper that takes care of storing the non-preserved bits into lsr_save_flags. Reviewed-by: Andy Shevchenko Signed-off-by: Ilpo J=C3=A4rvinen Link: https://lore.kernel.org/r/20220608095431.18376-3-ilpo.jarvinen@linux.= intel.com Signed-off-by: Greg Kroah-Hartman Signed-off-by: Sasha Levin --- drivers/tty/serial/8250/8250.h | 20 ++++++++++++++++++++ drivers/tty/serial/8250/8250_core.c | 3 +-- drivers/tty/serial/8250/8250_port.c | 15 ++++----------- 3 files changed, 25 insertions(+), 13 deletions(-) diff --git a/drivers/tty/serial/8250/8250.h b/drivers/tty/serial/8250/8250.h index 696030cfcb09..c89cb881d9b0 100644 --- a/drivers/tty/serial/8250/8250.h +++ b/drivers/tty/serial/8250/8250.h @@ -123,6 +123,26 @@ static inline void serial_out(struct uart_8250_port *u= p, int offset, int value) up->port.serial_out(&up->port, offset, value); } =20 +/** + * serial_lsr_in - Read LSR register and preserve flags across reads + * @up: uart 8250 port + * + * Read LSR register and handle saving non-preserved flags across reads. + * The flags that are not preserved across reads are stored into + * up->lsr_saved_flags. + * + * Returns LSR value or'ed with the preserved flags (if any). + */ +static inline unsigned int serial_lsr_in(struct uart_8250_port *up) +{ + unsigned int lsr =3D up->lsr_saved_flags; + + lsr |=3D serial_in(up, UART_LSR); + up->lsr_saved_flags =3D lsr & LSR_SAVE_FLAGS; + + return lsr; +} + /* * For the 16C950 */ diff --git a/drivers/tty/serial/8250/8250_core.c b/drivers/tty/serial/8250/= 8250_core.c index 3f56dbc9432b..82726cda6066 100644 --- a/drivers/tty/serial/8250/8250_core.c +++ b/drivers/tty/serial/8250/8250_core.c @@ -277,8 +277,7 @@ static void serial8250_backup_timeout(struct timer_list= *t) * the "Diva" UART used on the management processor on many HP * ia64 and parisc boxes. */ - lsr =3D serial_in(up, UART_LSR); - up->lsr_saved_flags |=3D lsr & LSR_SAVE_FLAGS; + lsr =3D serial_lsr_in(up); if ((iir & UART_IIR_NO_INT) && (up->ier & UART_IER_THRI) && (!uart_circ_empty(&up->port.state->xmit) || up->port.x_char) && (lsr & UART_LSR_THRE)) { diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/= 8250_port.c index 3c36a06a20b0..c9d8c0de56e5 100644 --- a/drivers/tty/serial/8250/8250_port.c +++ b/drivers/tty/serial/8250/8250_port.c @@ -1514,11 +1514,9 @@ static inline void __stop_tx(struct uart_8250_port *= p) struct uart_8250_em485 *em485 =3D p->em485; =20 if (em485) { - unsigned char lsr =3D serial_in(p, UART_LSR); + unsigned char lsr =3D serial_lsr_in(p); u64 stop_delay =3D 0; =20 - p->lsr_saved_flags |=3D lsr & LSR_SAVE_FLAGS; - if (!(lsr & UART_LSR_THRE)) return; /* @@ -1573,10 +1571,8 @@ static inline void __start_tx(struct uart_port *port) =20 if (serial8250_set_THRI(up)) { if (up->bugs & UART_BUG_TXEN) { - unsigned char lsr; + unsigned char lsr =3D serial_lsr_in(up); =20 - lsr =3D serial_in(up, UART_LSR); - up->lsr_saved_flags |=3D lsr & LSR_SAVE_FLAGS; if (lsr & UART_LSR_THRE) serial8250_tx_chars(up); } @@ -2007,8 +2003,7 @@ static unsigned int serial8250_tx_empty(struct uart_p= ort *port) serial8250_rpm_get(up); =20 spin_lock_irqsave(&port->lock, flags); - lsr =3D serial_port_in(port, UART_LSR); - up->lsr_saved_flags |=3D lsr & LSR_SAVE_FLAGS; + lsr =3D serial_lsr_in(up); spin_unlock_irqrestore(&port->lock, flags); =20 serial8250_rpm_put(up); @@ -2084,9 +2079,7 @@ static void wait_for_lsr(struct uart_8250_port *up, i= nt bits) =20 /* Wait up to 10ms for the character(s) to be sent. */ for (;;) { - status =3D serial_in(up, UART_LSR); - - up->lsr_saved_flags |=3D status & LSR_SAVE_FLAGS; + status =3D serial_lsr_in(up); =20 if ((status & bits) =3D=3D bits) break; --=20 2.35.1