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    Subject[PATCH AUTOSEL for 4.9 166/281] rtc: opal: Handle disabled TPO in opal_get_tpo_time()
    Date
    From: Vaibhav Jain <vaibhav@linux.vnet.ibm.com>

    [ Upstream commit 6dc1cf6f932bb0ea4d8f5e913a0a401ecacd2f03 ]

    On PowerNV platform when Timed-Power-On(TPO) is disabled, read of
    stored TPO yields value with all date components set to '0' inside
    opal_get_tpo_time(). The function opal_to_tm() then converts it to an
    offset from year 1900 yielding alarm-time == "1900-00-01
    00:00:00". This causes problems with __rtc_read_alarm() that
    expecting an offset from "1970-00-01 00:00:00" and returned alarm-time
    results in a -ve value for time64_t. Which ultimately results in this
    error reported in kernel logs with a seemingly garbage value:

    "rtc rtc0: invalid alarm value: -2-1--1041528741
    2005511117:71582844:32"

    We fix this by explicitly handling the case of all alarm date-time
    components being '0' inside opal_get_tpo_time() and returning -ENOENT
    in such a case. This signals generic rtc that no alarm is set and it
    bails out from the alarm initialization flow without reporting the
    above error.

    Signed-off-by: Vaibhav Jain <vaibhav@linux.vnet.ibm.com>
    Reported-by: Steve Best <sbest@redhat.com>
    Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
    Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
    ---
    drivers/rtc/rtc-opal.c | 10 ++++++++++
    1 file changed, 10 insertions(+)

    diff --git a/drivers/rtc/rtc-opal.c b/drivers/rtc/rtc-opal.c
    index e4324dcf9508..aa53fceaa5e0 100644
    --- a/drivers/rtc/rtc-opal.c
    +++ b/drivers/rtc/rtc-opal.c
    @@ -150,6 +150,16 @@ static int opal_get_tpo_time(struct device *dev, struct rtc_wkalrm *alarm)

    y_m_d = be32_to_cpu(__y_m_d);
    h_m_s_ms = ((u64)be32_to_cpu(__h_m) << 32);
    +
    + /* check if no alarm is set */
    + if (y_m_d == 0 && h_m_s_ms == 0) {
    + pr_debug("No alarm is set\n");
    + rc = -ENOENT;
    + goto exit;
    + } else {
    + pr_debug("Alarm set to %x %llx\n", y_m_d, h_m_s_ms);
    + }
    +
    opal_to_tm(y_m_d, h_m_s_ms, &alarm->time);

    exit:
    --
    2.14.1
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