| From 5b8b58063029f02da573120ef4dc9079822e3cda Mon Sep 17 00:00:00 2001 |
| From: Stewart Smith <stewart@linux.vnet.ibm.com> |
| Date: Tue, 2 Aug 2016 11:50:16 +1000 |
| Subject: rtc-opal: Fix handling of firmware error codes, prevent busy loops |
| |
| From: Stewart Smith <stewart@linux.vnet.ibm.com> |
| |
| 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 <stewart@linux.vnet.ibm.com> |
| Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| |
| --- |
| 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; |