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rtc-opal: Fix handling of firmware error codes, prevent busy loops

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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>
This commit is contained in:
Stewart Smith 2016-08-02 11:50:16 +10:00 committed by Michael Ellerman
parent 77720c8291
commit 5b8b580630
1 changed files with 10 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

12
drivers/rtc/rtc-opal.c
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@ -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;