From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1161303AbcE3OTn (ORCPT ); Mon, 30 May 2016 10:19:43 -0400 Received: from mailout2.w1.samsung.com ([210.118.77.12]:10719 "EHLO mailout2.w1.samsung.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754874AbcE3OTl (ORCPT ); Mon, 30 May 2016 10:19:41 -0400 X-AuditID: cbfec7f5-f792a6d000001302-9c-574c4bf93479 From: Krzysztof Kozlowski To: Greg Kroah-Hartman , Jiri Slaby , linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Chanwoo Choi , Bartlomiej Zolnierkiewicz , stable@vger.kernel.org, Krzysztof Kozlowski Subject: [PATCH stable] serial: samsung: Reorder the sequence of clock control when call s3c24xx_serial_set_termios() Date: Mon, 30 May 2016 16:19:10 +0200 Message-id: <1464617950-11595-1-git-send-email-k.kozlowski@samsung.com> X-Mailer: git-send-email 1.9.1 X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFvrDJMWRmVeSWpSXmKPExsVy+t/xq7o/vX3CDc79VbbYOGM9q8X1L89Z LZoXr2ezmLLhA5PF6xeGFpd3zWGzOLO4l91iwcZHjA4cHvvnrmH36NuyitFj/ZarLB6fN8kF sERx2aSk5mSWpRbp2yVwZdxvPsdUcE+ion3nDeYGxpOiXYycHBICJhJvFn1ghLDFJC7cW8/W xcjFISSwlFHi+LpZjBBOI5PE9uNXmUGq2ASMJTYvXwJWJSIwkVHi2OFtLCAOs8BKRom27gdM XYwcHMIC5RJPruSCNLAIqErMOrMMrJlXwF3ixbrV7BDr5CROHpvMOoGRewEjwypG0dTS5ILi pPRcI73ixNzi0rx0veT83E2MkDD5uoNx6TGrQ4wCHIxKPLwFmt7hQqyJZcWVuYcYJTiYlUR4 d3j5hAvxpiRWVqUW5ccXleakFh9ilOZgURLnnbnrfYiQQHpiSWp2ampBahFMlomDU6qBcYXz fhPPMxVBD/OrLjbfCS802XHo86uPdtwbHeRe/vmhzbBg/3TN/NzkaQeal+7x+qIkun5KWmJq wuvrs81WPN6r/Y1bTu75/rrS0yfNbH6ZN8dJczy47Cp/sbPszxGf6+oy8z5vlYg9nMT2g8Pb 7Wqs7VyvR/fuS/bm/PpzVForwYsz6+YOSSWW4oxEQy3mouJEAJQHKFMPAgAA Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Chanwoo Choi commit b8995f527aac143e83d3900ff39357651ea4e0f6 upstream. This patch fixes the broken serial log when changing the clock source of uart device. Before disabling the original clock source, this patch enables the new clock source to protect the clock off state for a split second. [k.kozlowski]: On SMP systems this opens a short time window when both clocks (old and new) are disabled and a second thread uses TTY/UART. This leads to broken log or imprecise external abort (on one of ARM64 boards): Unhandled fault: synchronous external abort (0x96000210) at 0xffffff8008080008 Internal error: : 96000210 [#1] PREEMPT SMP [] s3c24xx_serial_console_putchar+0x8/0x64 [] s3c24xx_serial_console_write+0x30/0x38 [] call_console_drivers.constprop.22+0x100/0x108 [] console_unlock+0x504/0x58c [] vprintk_emit+0x2cc/0x478 [] vprintk_default+0x38/0x40 [] printk+0xac/0xb8 [] audit_printk_skb+0x68/0x6c [] audit_log_end+0x13c/0x188 [] common_lsm_audit+0xb4/0x618 [] smack_log+0xe8/0x10c [] smk_tskacc+0x8c/0xa4 [] smk_curacc+0x2c/0x34 [] smack_inode_permission+0x60/0x70 [] security_inode_permission+0x58/0x80 [] __inode_permission+0x40/0xa0 [] inode_permission+0x14/0x4c [] may_open+0x5c/0x10c [] path_openat+0x13c/0xec8 [] do_filp_open+0x64/0xc0 [] do_sys_open+0x144/0x208 [] SyS_openat+0x10/0x18 [] __sys_trace_return+0x0/0x4 Signed-off-by: Chanwoo Choi Reviewed-by: Marek Szyprowski Signed-off-by: Greg Kroah-Hartman Cc: Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") [k.kozlowski: Backport to stable, update commit msg] Signed-off-by: Krzysztof Kozlowski --- The original Samsung serial driver was broken so this should be backported as far as possible including the 2.6.12. :) --- drivers/tty/serial/samsung.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/tty/serial/samsung.c b/drivers/tty/serial/samsung.c index ac7f8df54406..99bb23161dd6 100644 --- a/drivers/tty/serial/samsung.c +++ b/drivers/tty/serial/samsung.c @@ -1271,6 +1271,8 @@ static void s3c24xx_serial_set_termios(struct uart_port *port, /* check to see if we need to change clock source */ if (ourport->baudclk != clk) { + clk_prepare_enable(clk); + s3c24xx_serial_setsource(port, clk_sel); if (!IS_ERR(ourport->baudclk)) { @@ -1278,8 +1280,6 @@ static void s3c24xx_serial_set_termios(struct uart_port *port, ourport->baudclk = ERR_PTR(-EINVAL); } - clk_prepare_enable(clk); - ourport->baudclk = clk; ourport->baudclk_rate = clk ? clk_get_rate(clk) : 0; } -- 1.9.1