From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753167Ab3J2SHV (ORCPT ); Tue, 29 Oct 2013 14:07:21 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:59290 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752285Ab3J2SFN (ORCPT ); Tue, 29 Oct 2013 14:05:13 -0400 From: Kamal Mostafa To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: Henrik Rydberg , Guenter Roeck , Kamal Mostafa Subject: [PATCH 3.8 09/81] hwmon: (applesmc) Always read until end of data Date: Tue, 29 Oct 2013 11:03:30 -0700 Message-Id: <1383069882-11437-10-git-send-email-kamal@canonical.com> X-Mailer: git-send-email 1.8.1.2 In-Reply-To: <1383069882-11437-1-git-send-email-kamal@canonical.com> References: <1383069882-11437-1-git-send-email-kamal@canonical.com> X-Extended-Stable: 3.8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.8.13.12 -stable review patch. If anyone has any objections, please let me know. ------------------ From: Henrik Rydberg commit 25f2bd7f5add608c1d1405938f39c96927b275ca upstream. The crash reported and investigated in commit 5f4513 turned out to be caused by a change to the read interface on newer (2012) SMCs. Tests by Chris show that simply reading the data valid line is enough for the problem to go away. Additional tests show that the newer SMCs no longer wait for the number of requested bytes, but start sending data right away. Apparently the number of bytes to read is no longer specified as before, but instead found out by reading until end of data. Failure to read until end of data confuses the state machine, which eventually causes the crash. As a remedy, assuming bit0 is the read valid line, make sure there is nothing more to read before leaving the read function. Tested to resolve the original problem, and runtested on MBA3,1, MBP4,1, MBP8,2, MBP10,1, MBP10,2. The patch seems to have no effect on machines before 2012. Tested-by: Chris Murphy Signed-off-by: Henrik Rydberg Signed-off-by: Guenter Roeck Signed-off-by: Kamal Mostafa --- drivers/hwmon/applesmc.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/drivers/hwmon/applesmc.c b/drivers/hwmon/applesmc.c index f75abcc..0f646a7 100644 --- a/drivers/hwmon/applesmc.c +++ b/drivers/hwmon/applesmc.c @@ -230,6 +230,7 @@ static int send_argument(const char *key) static int read_smc(u8 cmd, const char *key, u8 *buffer, u8 len) { + u8 status, data = 0; int i; if (send_command(cmd) || send_argument(key)) { @@ -237,6 +238,7 @@ static int read_smc(u8 cmd, const char *key, u8 *buffer, u8 len) return -EIO; } + /* This has no effect on newer (2012) SMCs */ if (send_byte(len, APPLESMC_DATA_PORT)) { pr_warn("%.4s: read len fail\n", key); return -EIO; @@ -250,6 +252,17 @@ static int read_smc(u8 cmd, const char *key, u8 *buffer, u8 len) buffer[i] = inb(APPLESMC_DATA_PORT); } + /* Read the data port until bit0 is cleared */ + for (i = 0; i < 16; i++) { + udelay(APPLESMC_MIN_WAIT); + status = inb(APPLESMC_CMD_PORT); + if (!(status & 0x01)) + break; + data = inb(APPLESMC_DATA_PORT); + } + if (i) + pr_warn("flushed %d bytes, last value is: %d\n", i, data); + return 0; } -- 1.8.1.2