From patchwork Fri Aug 15 17:42:32 2014 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sebastian Andrzej Siewior X-Patchwork-Id: 4728751 Return-Path: X-Original-To: patchwork-linux-arm@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork1.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.19.201]) by patchwork1.web.kernel.org (Postfix) with ESMTP id 18AE19F38D for ; Fri, 15 Aug 2014 17:47:05 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 3AA8620117 for ; Fri, 15 Aug 2014 17:47:04 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.9]) (using TLSv1.2 with cipher DHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 642E220103 for ; Fri, 15 Aug 2014 17:47:03 +0000 (UTC) Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.80.1 #2 (Red Hat Linux)) id 1XILXf-0001gr-6O; Fri, 15 Aug 2014 17:43:55 +0000 Received: from galois.linutronix.de ([2001:470:1f0b:db:abcd:42:0:1]) by bombadil.infradead.org with esmtps (Exim 4.80.1 #2 (Red Hat Linux)) id 1XILX9-0001R4-Ej for linux-arm-kernel@lists.infradead.org; Fri, 15 Aug 2014 17:43:24 +0000 Received: from localhost ([127.0.0.1] helo=bazinga.breakpoint.cc) by Galois.linutronix.de with esmtp (Exim 4.80) (envelope-from ) id 1XILWf-0006sE-QW; Fri, 15 Aug 2014 19:42:53 +0200 From: Sebastian Andrzej Siewior To: linux-serial@vger.kernel.org Subject: [PATCH 04/15] tty: serial: 8250_core: read only RX if there is something in the FIFO Date: Fri, 15 Aug 2014 19:42:32 +0200 Message-Id: <1408124563-31541-5-git-send-email-bigeasy@linutronix.de> X-Mailer: git-send-email 2.0.1 In-Reply-To: <1408124563-31541-1-git-send-email-bigeasy@linutronix.de> References: <1408124563-31541-1-git-send-email-bigeasy@linutronix.de> X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1, SHORTCIRCUIT=-0.0001 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20140815_104323_699960_4073D80F X-CRM114-Status: GOOD ( 12.30 ) X-Spam-Score: -0.7 (/) Cc: tony@atomide.com, Greg Kroah-Hartman , Sebastian Andrzej Siewior , linux-kernel@vger.kernel.org, balbi@ti.com, Vinod Koul , linux-omap@vger.kernel.org, linux-arm-kernel@lists.infradead.org X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.18-1 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org X-Spam-Status: No, score=-2.6 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_NONE, RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP The serial8250_do_startup() function unconditionally clears the interrupts and for that it reads from the RX-FIFO without checking if there is a byte in the FIFO or not. This works fine on OMAP4+ HW like AM335x or DRA7. OMAP3630 ES1.1 (which means probably all OMAP3 and earlier) does not like this: |Unhandled fault: external abort on non-linefetch (0x1028) at 0xfb020000 |Internal error: : 1028 [#1] ARM |Modules linked in: |CPU: 0 PID: 1 Comm: swapper Not tainted 3.16.0-00022-g7edcb57-dirty #1213 |task: de0572c0 ti: de058000 task.ti: de058000 |PC is at mem32_serial_in+0xc/0x1c |LR is at serial8250_do_startup+0x220/0x85c |Flags: nzCv IRQs on FIQs on Mode SVC_32 ISA ARM Segment kernel |Control: 10c5387d Table: 80004019 DAC: 00000015 |[] (mem32_serial_in) from [] (serial8250_do_startup+0x220/0x85c) |[] (serial8250_do_startup) from [] (omap_8250_startup+0x5c/0xe0) |[] (omap_8250_startup) from [] (serial8250_startup+0x18/0x2c) |[] (serial8250_startup) from [] (uart_startup+0x78/0x1d8) |[] (uart_startup) from [] (uart_open+0xe8/0x114) |[] (uart_open) from [] (tty_open+0x1a8/0x5a4) Signed-off-by: Sebastian Andrzej Siewior --- drivers/tty/serial/8250/8250_core.c | 11 ++++++----- 1 file changed, 6 insertions(+), 5 deletions(-) diff --git a/drivers/tty/serial/8250/8250_core.c b/drivers/tty/serial/8250/8250_core.c index ae268e3..cc90c19 100644 --- a/drivers/tty/serial/8250/8250_core.c +++ b/drivers/tty/serial/8250/8250_core.c @@ -2087,8 +2087,8 @@ int serial8250_do_startup(struct uart_port *port) /* * Clear the interrupt registers. */ - serial_port_in(port, UART_LSR); - serial_port_in(port, UART_RX); + if (serial_port_in(port, UART_LSR) & UART_LSR_DR) + serial_port_in(port, UART_RX); serial_port_in(port, UART_IIR); serial_port_in(port, UART_MSR); @@ -2249,8 +2249,8 @@ int serial8250_do_startup(struct uart_port *port) * saved flags to avoid getting false values from polling * routines or the previous session. */ - serial_port_in(port, UART_LSR); - serial_port_in(port, UART_RX); + if (serial_port_in(port, UART_LSR) & UART_LSR_DR) + serial_port_in(port, UART_RX); serial_port_in(port, UART_IIR); serial_port_in(port, UART_MSR); up->lsr_saved_flags = 0; @@ -2344,7 +2344,8 @@ void serial8250_do_shutdown(struct uart_port *port) * Read data port to reset things, and then unlink from * the IRQ chain. */ - serial_port_in(port, UART_RX); + if (serial_port_in(port, UART_LSR) & UART_LSR_DR) + serial_port_in(port, UART_RX); serial8250_rpm_put(up); del_timer_sync(&up->timer);