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Commit 5b8b5806 authored by Stewart Smith's avatar Stewart Smith Committed by Michael Ellerman
Browse files

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



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: 16b1d26e ("rtc/tpo: Driver to support rtc and wakeup on PowerNV platform")
Cc: stable@vger.kernel.org # v3.19+
Signed-off-by: default avatarStewart Smith <stewart@linux.vnet.ibm.com>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
parent 77720c82

drivers/rtc/rtc-opal.c

+10 −2
Original line number Original line Diff line number Diff line
@@ -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)

static int opal_get_rtc_time(struct device *dev, struct rtc_time *tm)

{

{

	long rc = OPAL_BUSY;

	long rc = OPAL_BUSY;

	int retries = 10;

	u32 y_m_d;

	u32 y_m_d;

	u64 h_m_s_ms;

	u64 h_m_s_ms;

	__be32 __y_m_d;

	__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);

		rc = opal_rtc_read(&__y_m_d, &__h_m_s_ms);

		if (rc == OPAL_BUSY_EVENT)

		if (rc == OPAL_BUSY_EVENT)

			opal_poll_events(NULL);

			opal_poll_events(NULL);

		else

		else if (retries-- && (rc == OPAL_HARDWARE

				       || rc == OPAL_INTERNAL_ERROR))

			msleep(10);

			msleep(10);

		else if (rc != OPAL_BUSY && rc != OPAL_BUSY_EVENT)

			break;

	}

	}





	if (rc != OPAL_SUCCESS)

	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)

static int opal_set_rtc_time(struct device *dev, struct rtc_time *tm)

{

{

	long rc = OPAL_BUSY;

	long rc = OPAL_BUSY;

	int retries = 10;

	u32 y_m_d = 0;

	u32 y_m_d = 0;

	u64 h_m_s_ms = 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);

		rc = opal_rtc_write(y_m_d, h_m_s_ms);

		if (rc == OPAL_BUSY_EVENT)

		if (rc == OPAL_BUSY_EVENT)

			opal_poll_events(NULL);

			opal_poll_events(NULL);

		else

		else if (retries-- && (rc == OPAL_HARDWARE

				       || rc == OPAL_INTERNAL_ERROR))

			msleep(10);

			msleep(10);

		else if (rc != OPAL_BUSY && rc != OPAL_BUSY_EVENT)

			break;

	}

	}





	return rc == OPAL_SUCCESS ? 0 : -EIO;

	return rc == OPAL_SUCCESS ? 0 : -EIO;