From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:45356 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S936419AbeBUNLl (ORCPT ); Wed, 21 Feb 2018 08:11:41 -0500 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Stewart Smith , Michael Ellerman Subject: [PATCH 4.15 099/163] rtc-opal: Fix handling of firmware error codes, prevent busy loops Date: Wed, 21 Feb 2018 13:48:48 +0100 Message-Id: <20180221124535.766623327@linuxfoundation.org> In-Reply-To: <20180221124529.931834518@linuxfoundation.org> References: <20180221124529.931834518@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: stable-owner@vger.kernel.org List-ID: 4.15-stable review patch. If anyone has any objections, please let me know. ------------------ From: Stewart Smith commit 5b8b58063029f02da573120ef4dc9079822e3cda upstream. According to the OPAL docs: skiboot-5.2.5/doc/opal-api/opal-rtc-read-3.txt skiboot-5.2.5/doc/opal-api/opal-rtc-write-4.txt OPAL_HARDWARE may be returned from OPAL_RTC_READ or OPAL_RTC_WRITE and this indicates either a transient or permanent error. Prior to this patch, Linux was not dealing with OPAL_HARDWARE being a permanent error particularly well, in that you could end up in a busy loop. This was not too hard to trigger on an AMI BMC based OpenPOWER machine doing a continuous "ipmitool mc reset cold" to the BMC, the result of that being that we'd get stuck in an infinite loop in opal_get_rtc_time(). We now retry a few times before returning the error higher up the stack. Fixes: 16b1d26e77b1 ("rtc/tpo: Driver to support rtc and wakeup on PowerNV platform") Cc: stable@vger.kernel.org # v3.19+ Signed-off-by: Stewart Smith Signed-off-by: Michael Ellerman Signed-off-by: Greg Kroah-Hartman --- drivers/rtc/rtc-opal.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) --- a/drivers/rtc/rtc-opal.c +++ b/drivers/rtc/rtc-opal.c @@ -58,6 +58,7 @@ static void tm_to_opal(struct rtc_time * static int opal_get_rtc_time(struct device *dev, struct rtc_time *tm) { long rc = OPAL_BUSY; + int retries = 10; u32 y_m_d; u64 h_m_s_ms; __be32 __y_m_d; @@ -67,8 +68,11 @@ static int opal_get_rtc_time(struct devi rc = opal_rtc_read(&__y_m_d, &__h_m_s_ms); if (rc == OPAL_BUSY_EVENT) opal_poll_events(NULL); - else + else if (retries-- && (rc == OPAL_HARDWARE + || rc == OPAL_INTERNAL_ERROR)) msleep(10); + else if (rc != OPAL_BUSY && rc != OPAL_BUSY_EVENT) + break; } if (rc != OPAL_SUCCESS) @@ -84,6 +88,7 @@ static int opal_get_rtc_time(struct devi static int opal_set_rtc_time(struct device *dev, struct rtc_time *tm) { long rc = OPAL_BUSY; + int retries = 10; u32 y_m_d = 0; u64 h_m_s_ms = 0; @@ -92,8 +97,11 @@ static int opal_set_rtc_time(struct devi rc = opal_rtc_write(y_m_d, h_m_s_ms); if (rc == OPAL_BUSY_EVENT) opal_poll_events(NULL); - else + else if (retries-- && (rc == OPAL_HARDWARE + || rc == OPAL_INTERNAL_ERROR)) msleep(10); + else if (rc != OPAL_BUSY && rc != OPAL_BUSY_EVENT) + break; } return rc == OPAL_SUCCESS ? 0 : -EIO;