From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0a-001b2d01.pphosted.com (mx0a-001b2d01.pphosted.com [148.163.156.1]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 3s3K0W0RzWzDqVH for ; Tue, 2 Aug 2016 11:50:34 +1000 (AEST) Received: from pps.filterd (m0098396.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.11/8.16.0.11) with SMTP id u721mgRm139406 for ; Mon, 1 Aug 2016 21:50:32 -0400 Received: from e34.co.us.ibm.com (e34.co.us.ibm.com [32.97.110.152]) by mx0a-001b2d01.pphosted.com with ESMTP id 24gpjfcam2-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Mon, 01 Aug 2016 21:50:31 -0400 Received: from localhost by e34.co.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Mon, 1 Aug 2016 19:50:31 -0600 From: Stewart Smith To: linuxppc-dev@lists.ozlabs.org Cc: neelegup@linux.vnet.ibm.com, Stewart Smith , stable@vger.kernel.org Subject: [PATCH] rtc-opal: Fix handling of firmware error codes, prevent busy loops Date: Tue, 2 Aug 2016 11:50:16 +1000 Message-Id: <1470102616-18346-1-git-send-email-stewart@linux.vnet.ibm.com> List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , According to the OPAL docs: https://github.com/open-power/skiboot/blob/skiboot-5.2.5/doc/opal-api/opal-rtc-read-3.txt https://github.com/open-power/skiboot/blob/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. Cc: stable@vger.kernel.org Signed-off-by: Stewart Smith --- drivers/rtc/rtc-opal.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) diff --git a/drivers/rtc/rtc-opal.c b/drivers/rtc/rtc-opal.c index 9c18d6fd8107..fab19e3e2fba 100644 --- a/drivers/rtc/rtc-opal.c +++ b/drivers/rtc/rtc-opal.c @@ -58,6 +58,7 @@ static void tm_to_opal(struct rtc_time *tm, u32 *y_m_d, u64 *h_m_s_ms) 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 device *dev, struct rtc_time *tm) 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 device *dev, struct rtc_time *tm) 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 device *dev, struct rtc_time *tm) 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; -- 2.1.4